上一节我们分析了bootoader中传过来的cmdline中的命令是如何解析并执行的。
同时也是对bootloader中传过来的console进行了记录。
console也就是我们所说的控制台，可以是任何常见的输出设备，比如serial，比如framebuffer，比如网口。
本节主要以最常见的串口为例说明。
如果有搜索过内核代码，可以看到绝大多数的console都是串口设备。
所以内核对用作串口程序进行了进一步的封装，抽象出的serial_core.c文件中，对console的注册留有了接口。
console的注册函数是register_console，这个函数我们后面说。
void register_console(struct console *newcon)
这里我们先简单看一下串口驱动。
这里以三星的为例，这里不会详细分析代码，只会说一下串口驱动的架构。
串口驱动主要由下面这个来表示
struct uart_driver {
struct module *owner;
const char *driver_name;
const char *dev_name;
int major;
int minor;
int nr;
struct console *cons;
/*
* these are private; the low level driver should not
* touch these; they should be initialised to NULL
*/
struct uart_state *state;
struct tty_driver *tty_driver;
};
三星的实现如下，这里的console是console使用的
static struct uart_driver s3c24xx_uart_drv = {
.owner = THIS_MODULE,
.driver_name = "s3c2410_serial",
.nr = CONFIG_SERIAL_SAMSUNG_UARTS,
.cons = S3C24XX_SERIAL_CONSOLE,
.dev_name = S3C24XX_SERIAL_NAME,
.major = S3C24XX_SERIAL_MAJOR,
.minor = S3C24XX_SERIAL_MINOR,
};
static struct console s3c24xx_serial_console = {
.name = S3C24XX_SERIAL_NAME,
.device = uart_console_device,
.flags = CON_PRINTBUFFER,
.index = -1,
.write = s3c24xx_serial_console_write,
.setup = s3c24xx_serial_console_setup,
.data = &s3c24xx_uart_drv,
};
#define S3C24XX_SERIAL_NAME "ttySAC"
#define S3C24XX_SERIAL_MAJOR 204
#define S3C24XX_SERIAL_MINOR 64
/* 串口设备数量由具体的CPU决定 */
CONFIG_SERIAL_SAMSUNG_UARTS这里我们只关注名字为"ttySAC"，所以我们uboot的传参就是console = "ttySACx"
后面的这个x，内核解析为了index。
接下来再看一下一个uart端口是如何描述
内核抽象出了公共的部分。
struct uart_port {
spinlock_t lock; /* port lock */
unsigned long iobase; /* in/out[bwl] */
unsigned char __iomem *membase; /* read/write[bwl] */
unsigned int (*serial_in)(struct uart_port *, int);
void (*serial_out)(struct uart_port *, int, int);
void (*set_termios)(struct uart_port *,
struct ktermios *new,
struct ktermios *old);
void (*set_ldisc)(struct uart_port *,
struct ktermios *);
unsigned int (*get_mctrl)(struct uart_port *);
void (*set_mctrl)(struct uart_port *, unsigned int);
unsigned int (*get_divisor)(struct uart_port *,
unsigned int baud,
unsigned int *frac);
void (*set_divisor)(struct uart_port *,
unsigned int baud,
unsigned int quot,
unsigned int quot_frac);
int (*startup)(struct uart_port *port);
void (*shutdown)(struct uart_port *port);
void (*throttle)(struct uart_port *port);
void (*unthrottle)(struct uart_port *port);
int (*handle_irq)(struct uart_port *);
void (*pm)(struct uart_port *, unsigned int state,
unsigned int old);
void (*handle_break)(struct uart_port *);
int (*rs485_config)(struct uart_port *,
struct serial_rs485 *rs485);
unsigned int irq; /* irq number */
unsigned long irqflags; /* irq flags */
unsigned int uartclk; /* base uart clock */
unsigned int fifosize; /* tx fifo size */
unsigned char x_char; /* xon/xoff char */
unsigned char regshift; /* reg offset shift */
unsigned char iotype; /* io access style */
unsigned char quirks; /* internal quirks */
#define UPIO_PORT (SERIAL_IO_PORT) /* 8b I/O port access */
#define UPIO_HUB6 (SERIAL_IO_HUB6) /* Hub6 ISA card */
#define UPIO_MEM (SERIAL_IO_MEM) /* driver-specific */
#define UPIO_MEM32 (SERIAL_IO_MEM32) /* 32b little endian */
#define UPIO_AU (SERIAL_IO_AU) /* Au1x00 and RT288x type IO */
#define UPIO_TSI (SERIAL_IO_TSI) /* Tsi108/109 type IO */
#define UPIO_MEM32BE (SERIAL_IO_MEM32BE) /* 32b big endian */
#define UPIO_MEM16 (SERIAL_IO_MEM16) /* 16b little endian */
/* quirks must be updated while holding port mutex */
#define UPQ_NO_TXEN_TEST BIT(0)
unsigned int read_status_mask; /* driver specific */
unsigned int ignore_status_mask; /* driver specific */
struct uart_state *state; /* pointer to parent state */
struct uart_icount icount; /* statistics */
struct console *cons; /* struct console, if any */
#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
unsigned long sysrq; /* sysrq timeout */
#endif
/* flags must be updated while holding port mutex */
upf_t flags;
/*
* These flags must be equivalent to the flags defined in
* include/uapi/linux/tty_flags.h which are the userspace definitions
* assigned from the serial_struct flags in uart_set_info()
* [for bit definitions in the UPF_CHANGE_MASK]
*
* Bits [0..UPF_LAST_USER] are userspace defined/visible/changeable
* The remaining bits are serial-core specific and not modifiable by
* userspace.
*/
#define UPF_FOURPORT ((__force upf_t) ASYNC_FOURPORT /* 1 */ )
#define UPF_SAK ((__force upf_t) ASYNC_SAK /* 2 */ )
#define UPF_SPD_HI ((__force upf_t) ASYNC_SPD_HI /* 4 */ )
#define UPF_SPD_VHI ((__force upf_t) ASYNC_SPD_VHI /* 5 */ )
#define UPF_SPD_CUST ((__force upf_t) ASYNC_SPD_CUST /* 0x0030 */ )
#define UPF_SPD_WARP ((__force upf_t) ASYNC_SPD_WARP /* 0x1010 */ )
#define UPF_SPD_MASK ((__force upf_t) ASYNC_SPD_MASK /* 0x1030 */ )
#define UPF_SKIP_TEST ((__force upf_t) ASYNC_SKIP_TEST /* 6 */ )
#define UPF_AUTO_IRQ ((__force upf_t) ASYNC_AUTO_IRQ /* 7 */ )
#define UPF_HARDPPS_CD ((__force upf_t) ASYNC_HARDPPS_CD /* 11 */ )
#define UPF_SPD_SHI ((__force upf_t) ASYNC_SPD_SHI /* 12 */ )
#define UPF_LOW_LATENCY ((__force upf_t) ASYNC_LOW_LATENCY /* 13 */ )
#define UPF_BUGGY_UART ((__force upf_t) ASYNC_BUGGY_UART /* 14 */ )
#define UPF_MAGIC_MULTIPLIER ((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ )
#define UPF_NO_THRE_TEST ((__force upf_t) (1 << 19))
/* Port has hardware-assisted h/w flow control */
#define UPF_AUTO_CTS ((__force upf_t) (1 << 20))
#define UPF_AUTO_RTS ((__force upf_t) (1 << 21))
#define UPF_HARD_FLOW ((__force upf_t) (UPF_AUTO_CTS | UPF_AUTO_RTS))
/* Port has hardware-assisted s/w flow control */
#define UPF_SOFT_FLOW ((__force upf_t) (1 << 22))
#define UPF_CONS_FLOW ((__force upf_t) (1 << 23))
#define UPF_SHARE_IRQ ((__force upf_t) (1 << 24))
#define UPF_EXAR_EFR ((__force upf_t) (1 << 25))
#define UPF_BUG_THRE ((__force upf_t) (1 << 26))
/* The exact UART type is known and should not be probed. */
#define UPF_FIXED_TYPE ((__force upf_t) (1 << 27))
#define UPF_BOOT_AUTOCONF ((__force upf_t) (1 << 28))
#define UPF_FIXED_PORT ((__force upf_t) (1 << 29))
#define UPF_DEAD ((__force upf_t) (1 << 30))
#define UPF_IOREMAP ((__force upf_t) (1 << 31))
#define __UPF_CHANGE_MASK 0x17fff
#define UPF_CHANGE_MASK ((__force upf_t) __UPF_CHANGE_MASK)
#define UPF_USR_MASK ((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY))
#if __UPF_CHANGE_MASK > ASYNC_FLAGS
#error Change mask not equivalent to userspace-visible bit defines
#endif
/*
* Must hold termios_rwsem, port mutex and port lock to change;
* can hold any one lock to read.
*/
upstat_t status;
#define UPSTAT_CTS_ENABLE ((__force upstat_t) (1 << 0))
#define UPSTAT_DCD_ENABLE ((__force upstat_t) (1 << 1))
#define UPSTAT_AUTORTS ((__force upstat_t) (1 << 2))
#define UPSTAT_AUTOCTS ((__force upstat_t) (1 << 3))
#define UPSTAT_AUTOXOFF ((__force upstat_t) (1 << 4))
#define UPSTAT_SYNC_FIFO ((__force upstat_t) (1 << 5))
int hw_stopped; /* sw-assisted CTS flow state */
unsigned int mctrl; /* current modem ctrl settings */
unsigned int timeout; /* character-based timeout */
unsigned int type; /* port type */
const struct uart_ops *ops;
unsigned int custom_divisor;
unsigned int line; /* port index */
unsigned int minor;
resource_size_t mapbase; /* for ioremap */
resource_size_t mapsize;
struct device *dev; /* parent device */
unsigned char hub6; /* this should be in the 8250 driver */
unsigned char suspended;
unsigned char unused[2];
const char *name; /* port name */
struct attribute_group *attr_group; /* port specific attributes */
const struct attribute_group **tty_groups; /* all attributes (serial core use only) */
struct serial_rs485 rs485;
void *private_data; /* generic platform data pointer */
};
不同厂家在内核的基础上继续封装实现自己独特的部分。
struct s3c24xx_uart_port {
unsigned char rx_claimed;
unsigned char tx_claimed;
unsigned int pm_level;
unsigned long baudclk_rate;
unsigned int min_dma_size;
unsigned int rx_irq;
unsigned int tx_irq;
unsigned int tx_in_progress;
unsigned int tx_mode;
unsigned int rx_mode;
struct s3c24xx_uart_info *info;
struct clk *clk;
struct clk *baudclk;
struct uart_port port;
struct s3c24xx_serial_drv_data *drv_data;
/* reference to platform data */
struct s3c2410_uartcfg *cfg;
struct s3c24xx_uart_dma *dma;
#ifdef CONFIG_ARM_S3C24XX_CPUFREQ
struct notifier_block freq_transition;
#endif
};三星一个SOC最多4个串口，所以这里根据配置最多定义了4个。
这里我们关注一个点，line，为串口的硬件编号，和次序一样。
#define __PORT_LOCK_UNLOCKED(i) \
__SPIN_LOCK_UNLOCKED(s3c24xx_serial_ports[i].port.lock)
static struct s3c24xx_uart_port
s3c24xx_serial_ports[CONFIG_SERIAL_SAMSUNG_UARTS] = {
[0] = {
.port = {
.lock = __PORT_LOCK_UNLOCKED(0),
.iotype = UPIO_MEM,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 0,
}
},
[1] = {
.port = {
.lock = __PORT_LOCK_UNLOCKED(1),
.iotype = UPIO_MEM,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 1,
}
},
#if CONFIG_SERIAL_SAMSUNG_UARTS > 2
[2] = {
.port = {
.lock = __PORT_LOCK_UNLOCKED(2),
.iotype = UPIO_MEM,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 2,
}
},
#endif
#if CONFIG_SERIAL_SAMSUNG_UARTS > 3
[3] = {
.port = {
.lock = __PORT_LOCK_UNLOCKED(3),
.iotype = UPIO_MEM,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 3,
}
}
#endif
};
#undef __PORT_LOCK_UNLOCKED其它标志之类比较常见，但其实我们都知道，重点在操作方法，也就是ops。
这是一个很复杂的结构，里面函数很多，但基本都是硬件操作相关的。这里就不再细看。
static struct uart_ops s3c24xx_serial_ops = {
.pm = s3c24xx_serial_pm,
.tx_empty = s3c24xx_serial_tx_empty,
.get_mctrl = s3c24xx_serial_get_mctrl,
.set_mctrl = s3c24xx_serial_set_mctrl,
.stop_tx = s3c24xx_serial_stop_tx,
.start_tx = s3c24xx_serial_start_tx,
.stop_rx = s3c24xx_serial_stop_rx,
.break_ctl = s3c24xx_serial_break_ctl,
.startup = s3c24xx_serial_startup,
.shutdown = s3c24xx_serial_shutdown,
.set_termios = s3c24xx_serial_set_termios,
.type = s3c24xx_serial_type,
.release_port = s3c24xx_serial_release_port,
.request_port = s3c24xx_serial_request_port,
.config_port = s3c24xx_serial_config_port,
.verify_port = s3c24xx_serial_verify_port,
#if defined(CONFIG_SERIAL_SAMSUNG_CONSOLE) && defined(CONFIG_CONSOLE_POLL)
.poll_get_char = s3c24xx_serial_get_poll_char,
.poll_put_char = s3c24xx_serial_put_poll_char,
#endif
};这里我们看一下驱动入口，
static const struct platform_device_id s3c24xx_serial_driver_ids[] = {
{
.name = "s3c2410-uart",
.driver_data = S3C2410_SERIAL_DRV_DATA,
}, {
.name = "s3c2412-uart",
.driver_data = S3C2412_SERIAL_DRV_DATA,
}, {
.name = "s3c2440-uart",
.driver_data = S3C2440_SERIAL_DRV_DATA,
}, {
.name = "s3c6400-uart",
.driver_data = S3C6400_SERIAL_DRV_DATA,
}, {
.name = "s5pv210-uart",
.driver_data = S5PV210_SERIAL_DRV_DATA,
}, {
.name = "exynos4210-uart",
.driver_data = EXYNOS4210_SERIAL_DRV_DATA,
}, {
.name = "exynos5433-uart",
.driver_data = EXYNOS5433_SERIAL_DRV_DATA,
},
{ },
};
MODULE_DEVICE_TABLE(platform, s3c24xx_serial_driver_ids);
#ifdef CONFIG_OF
static const struct of_device_id s3c24xx_uart_dt_match[] = {
{ .compatible = "samsung,s3c2410-uart",
.data = (void *)S3C2410_SERIAL_DRV_DATA },
{ .compatible = "samsung,s3c2412-uart",
.data = (void *)S3C2412_SERIAL_DRV_DATA },
{ .compatible = "samsung,s3c2440-uart",
.data = (void *)S3C2440_SERIAL_DRV_DATA },
{ .compatible = "samsung,s3c6400-uart",
.data = (void *)S3C6400_SERIAL_DRV_DATA },
{ .compatible = "samsung,s5pv210-uart",
.data = (void *)S5PV210_SERIAL_DRV_DATA },
{ .compatible = "samsung,exynos4210-uart",
.data = (void *)EXYNOS4210_SERIAL_DRV_DATA },
{ .compatible = "samsung,exynos5433-uart",
.data = (void *)EXYNOS5433_SERIAL_DRV_DATA },
{},
};
MODULE_DEVICE_TABLE(of, s3c24xx_uart_dt_match);
#endif
static struct platform_driver samsung_serial_driver = {
.probe = s3c24xx_serial_probe,
.remove = s3c24xx_serial_remove,
.id_table = s3c24xx_serial_driver_ids,
.driver = {
.name = "samsung-uart",
.pm = SERIAL_SAMSUNG_PM_OPS,
.of_match_table = of_match_ptr(s3c24xx_uart_dt_match),
},
};
module_platform_driver(samsung_serial_driver);
这里我们看一下不同的soc都绑定了自己的硬件特有的信息，比如fifo大小等。
#ifdef CONFIG_CPU_S3C2410
static struct s3c24xx_serial_drv_data s3c2410_serial_drv_data = {
.info = &(struct s3c24xx_uart_info) {
.name = "Samsung S3C2410 UART",
.type = PORT_S3C2410,
.fifosize = 16,
.rx_fifomask = S3C2410_UFSTAT_RXMASK,
.rx_fifoshift = S3C2410_UFSTAT_RXSHIFT,
.rx_fifofull = S3C2410_UFSTAT_RXFULL,
.tx_fifofull = S3C2410_UFSTAT_TXFULL,
.tx_fifomask = S3C2410_UFSTAT_TXMASK,
.tx_fifoshift = S3C2410_UFSTAT_TXSHIFT,
.def_clk_sel = S3C2410_UCON_CLKSEL0,
.num_clks = 2,
.clksel_mask = S3C2410_UCON_CLKMASK,
.clksel_shift = S3C2410_UCON_CLKSHIFT,
},
.def_cfg = &(struct s3c2410_uartcfg) {
.ucon = S3C2410_UCON_DEFAULT,
.ufcon = S3C2410_UFCON_DEFAULT,
},
};
#define S3C2410_SERIAL_DRV_DATA ((kernel_ulong_t)&s3c2410_serial_drv_data)
#else
#define S3C2410_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif
#ifdef CONFIG_CPU_S3C2412
static struct s3c24xx_serial_drv_data s3c2412_serial_drv_data = {
.info = &(struct s3c24xx_uart_info) {
.name = "Samsung S3C2412 UART",
.type = PORT_S3C2412,
.fifosize = 64,
.has_divslot = 1,
.rx_fifomask = S3C2440_UFSTAT_RXMASK,
.rx_fifoshift = S3C2440_UFSTAT_RXSHIFT,
.rx_fifofull = S3C2440_UFSTAT_RXFULL,
.tx_fifofull = S3C2440_UFSTAT_TXFULL,
.tx_fifomask = S3C2440_UFSTAT_TXMASK,
.tx_fifoshift = S3C2440_UFSTAT_TXSHIFT,
.def_clk_sel = S3C2410_UCON_CLKSEL2,
.num_clks = 4,
.clksel_mask = S3C2412_UCON_CLKMASK,
.clksel_shift = S3C2412_UCON_CLKSHIFT,
},
.def_cfg = &(struct s3c2410_uartcfg) {
.ucon = S3C2410_UCON_DEFAULT,
.ufcon = S3C2410_UFCON_DEFAULT,
},
};
#define S3C2412_SERIAL_DRV_DATA ((kernel_ulong_t)&s3c2412_serial_drv_data)
#else
#define S3C2412_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif
#if defined(CONFIG_CPU_S3C2440) || defined(CONFIG_CPU_S3C2416) || \
defined(CONFIG_CPU_S3C2443) || defined(CONFIG_CPU_S3C2442)
static struct s3c24xx_serial_drv_data s3c2440_serial_drv_data = {
.info = &(struct s3c24xx_uart_info) {
.name = "Samsung S3C2440 UART",
.type = PORT_S3C2440,
.fifosize = 64,
.has_divslot = 1,
.rx_fifomask = S3C2440_UFSTAT_RXMASK,
.rx_fifoshift = S3C2440_UFSTAT_RXSHIFT,
.rx_fifofull = S3C2440_UFSTAT_RXFULL,
.tx_fifofull = S3C2440_UFSTAT_TXFULL,
.tx_fifomask = S3C2440_UFSTAT_TXMASK,
.tx_fifoshift = S3C2440_UFSTAT_TXSHIFT,
.def_clk_sel = S3C2410_UCON_CLKSEL2,
.num_clks = 4,
.clksel_mask = S3C2412_UCON_CLKMASK,
.clksel_shift = S3C2412_UCON_CLKSHIFT,
},
.def_cfg = &(struct s3c2410_uartcfg) {
.ucon = S3C2410_UCON_DEFAULT,
.ufcon = S3C2410_UFCON_DEFAULT,
},
};
#define S3C2440_SERIAL_DRV_DATA ((kernel_ulong_t)&s3c2440_serial_drv_data)
#else
#define S3C2440_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif
#if defined(CONFIG_CPU_S3C6400) || defined(CONFIG_CPU_S3C6410)
static struct s3c24xx_serial_drv_data s3c6400_serial_drv_data = {
.info = &(struct s3c24xx_uart_info) {
.name = "Samsung S3C6400 UART",
.type = PORT_S3C6400,
.fifosize = 64,
.has_divslot = 1,
.rx_fifomask = S3C2440_UFSTAT_RXMASK,
.rx_fifoshift = S3C2440_UFSTAT_RXSHIFT,
.rx_fifofull = S3C2440_UFSTAT_RXFULL,
.tx_fifofull = S3C2440_UFSTAT_TXFULL,
.tx_fifomask = S3C2440_UFSTAT_TXMASK,
.tx_fifoshift = S3C2440_UFSTAT_TXSHIFT,
.def_clk_sel = S3C2410_UCON_CLKSEL2,
.num_clks = 4,
.clksel_mask = S3C6400_UCON_CLKMASK,
.clksel_shift = S3C6400_UCON_CLKSHIFT,
},
.def_cfg = &(struct s3c2410_uartcfg) {
.ucon = S3C2410_UCON_DEFAULT,
.ufcon = S3C2410_UFCON_DEFAULT,
},
};
#define S3C6400_SERIAL_DRV_DATA ((kernel_ulong_t)&s3c6400_serial_drv_data)
#else
#define S3C6400_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif
#ifdef CONFIG_CPU_S5PV210
static struct s3c24xx_serial_drv_data s5pv210_serial_drv_data = {
.info = &(struct s3c24xx_uart_info) {
.name = "Samsung S5PV210 UART",
.type = PORT_S3C6400,
.has_divslot = 1,
.rx_fifomask = S5PV210_UFSTAT_RXMASK,
.rx_fifoshift = S5PV210_UFSTAT_RXSHIFT,
.rx_fifofull = S5PV210_UFSTAT_RXFULL,
.tx_fifofull = S5PV210_UFSTAT_TXFULL,
.tx_fifomask = S5PV210_UFSTAT_TXMASK,
.tx_fifoshift = S5PV210_UFSTAT_TXSHIFT,
.def_clk_sel = S3C2410_UCON_CLKSEL0,
.num_clks = 2,
.clksel_mask = S5PV210_UCON_CLKMASK,
.clksel_shift = S5PV210_UCON_CLKSHIFT,
},
.def_cfg = &(struct s3c2410_uartcfg) {
.ucon = S5PV210_UCON_DEFAULT,
.ufcon = S5PV210_UFCON_DEFAULT,
},
.fifosize = { 256, 64, 16, 16 },
};
#define S5PV210_SERIAL_DRV_DATA ((kernel_ulong_t)&s5pv210_serial_drv_data)
#else
#define S5PV210_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif
#if defined(CONFIG_ARCH_EXYNOS)
#define EXYNOS_COMMON_SERIAL_DRV_DATA \
.info = &(struct s3c24xx_uart_info) { \
.name = "Samsung Exynos UART", \
.type = PORT_S3C6400, \
.has_divslot = 1, \
.rx_fifomask = S5PV210_UFSTAT_RXMASK, \
.rx_fifoshift = S5PV210_UFSTAT_RXSHIFT, \
.rx_fifofull = S5PV210_UFSTAT_RXFULL, \
.tx_fifofull = S5PV210_UFSTAT_TXFULL, \
.tx_fifomask = S5PV210_UFSTAT_TXMASK, \
.tx_fifoshift = S5PV210_UFSTAT_TXSHIFT, \
.def_clk_sel = S3C2410_UCON_CLKSEL0, \
.num_clks = 1, \
.clksel_mask = 0, \
.clksel_shift = 0, \
}, \
.def_cfg = &(struct s3c2410_uartcfg) { \
.ucon = S5PV210_UCON_DEFAULT, \
.ufcon = S5PV210_UFCON_DEFAULT, \
.has_fracval = 1, \
} \
static struct s3c24xx_serial_drv_data exynos4210_serial_drv_data = {
EXYNOS_COMMON_SERIAL_DRV_DATA,
.fifosize = { 256, 64, 16, 16 },
};
static struct s3c24xx_serial_drv_data exynos5433_serial_drv_data = {
EXYNOS_COMMON_SERIAL_DRV_DATA,
.fifosize = { 64, 256, 16, 256 },
};
#define EXYNOS4210_SERIAL_DRV_DATA ((kernel_ulong_t)&exynos4210_serial_drv_data)
#define EXYNOS5433_SERIAL_DRV_DATA ((kernel_ulong_t)&exynos5433_serial_drv_data)
#else
#define EXYNOS4210_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#define EXYNOS5433_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif
这里我们分析的4.19内核，设备树也是必须看的。
uart0: serial@e2900000 {
compatible = "samsung,s5pv210-uart";
reg = <0xe2900000 0x400>;
interrupt-parent = <&vic1>;
interrupts = <10>;
clock-names = "uart", "clk_uart_baud0",
"clk_uart_baud1";
clocks = <&clocks CLK_UART0>, <&clocks CLK_UART0>,
<&clocks SCLK_UART0>;
status = "disabled";
};
uart1: serial@e2900400 {
compatible = "samsung,s5pv210-uart";
reg = <0xe2900400 0x400>;
interrupt-parent = <&vic1>;
interrupts = <11>;
clock-names = "uart", "clk_uart_baud0",
"clk_uart_baud1";
clocks = <&clocks CLK_UART1>, <&clocks CLK_UART1>,
<&clocks SCLK_UART1>;
status = "disabled";
};
uart2: serial@e2900800 {
compatible = "samsung,s5pv210-uart";
reg = <0xe2900800 0x400>;
interrupt-parent = <&vic1>;
interrupts = <12>;
clock-names = "uart", "clk_uart_baud0",
"clk_uart_baud1";
clocks = <&clocks CLK_UART2>, <&clocks CLK_UART2>,
<&clocks SCLK_UART2>;
status = "disabled";
};
uart3: serial@e2900c00 {
compatible = "samsung,s5pv210-uart";
reg = <0xe2900c00 0x400>;
interrupt-parent = <&vic1>;
interrupts = <13>;
clock-names = "uart", "clk_uart_baud0",
"clk_uart_baud1";
clocks = <&clocks CLK_UART3>, <&clocks CLK_UART3>,
<&clocks SCLK_UART3>;
status = "disabled";
};
接下来这里就直接看probe
static int s3c24xx_serial_probe(struct platform_device *pdev)
{
struct device_node *np = pdev->dev.of_node;
struct s3c24xx_uart_port *ourport;
int index = probe_index;
int ret;
if (np) {
ret = of_alias_get_id(np, "serial");
if (ret >= 0)
index = ret;
}
dbg("s3c24xx_serial_probe(%p) %d\n", pdev, index);
if (index >= ARRAY_SIZE(s3c24xx_serial_ports)) {
dev_err(&pdev->dev, "serial%d out of range\n", index);
return -EINVAL;
}
ourport = &s3c24xx_serial_ports[index];
ourport->drv_data = s3c24xx_get_driver_data(pdev);
if (!ourport->drv_data) {
dev_err(&pdev->dev, "could not find driver data\n");
return -ENODEV;
}
ourport->baudclk = ERR_PTR(-EINVAL);
ourport->info = ourport->drv_data->info;
ourport->cfg = (dev_get_platdata(&pdev->dev)) ?
dev_get_platdata(&pdev->dev) :
ourport->drv_data->def_cfg;
if (np)
of_property_read_u32(np,
"samsung,uart-fifosize", &ourport->port.fifosize);
if (ourport->drv_data->fifosize[index])
ourport->port.fifosize = ourport->drv_data->fifosize[index];
else if (ourport->info->fifosize)
ourport->port.fifosize = ourport->info->fifosize;
/*
* DMA transfers must be aligned at least to cache line size,
* so find minimal transfer size suitable for DMA mode
*/
ourport->min_dma_size = max_t(int, ourport->port.fifosize,
dma_get_cache_alignment());
dbg("%s: initialising port %p...\n", __func__, ourport);
ret = s3c24xx_serial_init_port(ourport, pdev);
if (ret < 0)
return ret;
if (!s3c24xx_uart_drv.state) {
ret = uart_register_driver(&s3c24xx_uart_drv);
if (ret < 0) {
pr_err("Failed to register Samsung UART driver\n");
return ret;
}
}
dbg("%s: adding port\n", __func__);
uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);
platform_set_drvdata(pdev, &ourport->port);
/*
* Deactivate the clock enabled in s3c24xx_serial_init_port here,
* so that a potential re-enablement through the pm-callback overlaps
* and keeps the clock enabled in this case.
*/
clk_disable_unprepare(ourport->clk);
ret = s3c24xx_serial_cpufreq_register(ourport);
if (ret < 0)
dev_err(&pdev->dev, "failed to add cpufreq notifier\n");
probe_index++;
return 0;
}上面函数我们主要看四点。
1.序号，设备树有定义别名，优先使用设备树里面的，如何没有，则按注册时序编号。
static int s3c24xx_serial_probe(struct platform_device *pdev)
{
int index = probe_index;
int ret;
if (np) {
ret = of_alias_get_id(np, "serial");
if (ret >= 0)
index = ret;
}
.....
probe_index++;
return 0;
}设备树定义别名我们之前有过，三星默认是没定义的，定义的话也很简单serial0 = &uart0; serial1 = &uart1; ......
aliases {
csis0 = &csis0;
fimc0 = &fimc0;
fimc1 = &fimc1;
fimc2 = &fimc2;
i2c0 = &i2c0;
i2c1 = &i2c1;
i2c2 = &i2c2;
i2s0 = &i2s0;
i2s1 = &i2s1;
i2s2 = &i2s2;
pinctrl0 = &pinctrl0;
spi0 = &spi0;
spi1 = &spi1;
};
2.接下来就是去除设端口，根据设备获取对应的特有数据，初始化一些参数，进而进行硬件的初始化，中断申请，寄存器映射等。
ourport = &s3c24xx_serial_ports[index];
ourport->drv_data = s3c24xx_get_driver_data(pdev);
if (!ourport->drv_data) {
dev_err(&pdev->dev, "could not find driver data\n");
return -ENODEV;
}
ourport->baudclk = ERR_PTR(-EINVAL);
ourport->info = ourport->drv_data->info;
ourport->cfg = (dev_get_platdata(&pdev->dev)) ?
dev_get_platdata(&pdev->dev) :
ourport->drv_data->def_cfg;
if (np)
of_property_read_u32(np,
"samsung,uart-fifosize", &ourport->port.fifosize);
if (ourport->drv_data->fifosize[index])
ourport->port.fifosize = ourport->drv_data->fifosize[index];
else if (ourport->info->fifosize)
ourport->port.fifosize = ourport->info->fifosize;
/*
* DMA transfers must be aligned at least to cache line size,
* so find minimal transfer size suitable for DMA mode
*/
ourport->min_dma_size = max_t(int, ourport->port.fifosize,
dma_get_cache_alignment());
dbg("%s: initialising port %p...\n", __func__, ourport);
ret = s3c24xx_serial_init_port(ourport, pdev);
if (ret < 0)
return ret;
if (!s3c24xx_uart_drv.state) {
ret = uart_register_driver(&s3c24xx_uart_drv);
if (ret < 0) {
pr_err("Failed to register Samsung UART driver\n");
return ret;
}
}
当然这里我们就看一下资源串口初始化和资源申请，寄存器映射，当然中断这里申请了，在别的地方初始化的。
/* s3c24xx_serial_init_port
*
* initialise a single serial port from the platform device given
*/
static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
struct platform_device *platdev)
{
struct uart_port *port = &ourport->port;
struct s3c2410_uartcfg *cfg = ourport->cfg;
struct resource *res;
int ret;
dbg("s3c24xx_serial_init_port: port=%p, platdev=%p\n", port, platdev);
if (platdev == NULL)
return -ENODEV;
if (port->mapbase != 0)
return -EINVAL;
/* setup info for port */
port->dev = &platdev->dev;
/* Startup sequence is different for s3c64xx and higher SoC's */
if (s3c24xx_serial_has_interrupt_mask(port))
s3c24xx_serial_ops.startup = s3c64xx_serial_startup;
port->uartclk = 1;
if (cfg->uart_flags & UPF_CONS_FLOW) {
dbg("s3c24xx_serial_init_port: enabling flow control\n");
port->flags |= UPF_CONS_FLOW;
}
/* sort our the physical and virtual addresses for each UART */
res = platform_get_resource(platdev, IORESOURCE_MEM, 0);
if (res == NULL) {
dev_err(port->dev, "failed to find memory resource for uart\n");
return -EINVAL;
}
dbg("resource %pR)\n", res);
port->membase = devm_ioremap(port->dev, res->start, resource_size(res));
if (!port->membase) {
dev_err(port->dev, "failed to remap controller address\n");
return -EBUSY;
}
port->mapbase = res->start;
ret = platform_get_irq(platdev, 0);
if (ret < 0)
port->irq = 0;
else {
port->irq = ret;
ourport->rx_irq = ret;
ourport->tx_irq = ret + 1;
}
ret = platform_get_irq(platdev, 1);
if (ret > 0)
ourport->tx_irq = ret;
/*
* DMA is currently supported only on DT platforms, if DMA properties
* are specified.
*/
if (platdev->dev.of_node && of_find_property(platdev->dev.of_node,
"dmas", NULL)) {
ourport->dma = devm_kzalloc(port->dev,
sizeof(*ourport->dma),
GFP_KERNEL);
if (!ourport->dma) {
ret = -ENOMEM;
goto err;
}
}
ourport->clk = clk_get(&platdev->dev, "uart");
if (IS_ERR(ourport->clk)) {
pr_err("%s: Controller clock not found\n",
dev_name(&platdev->dev));
ret = PTR_ERR(ourport->clk);
goto err;
}
ret = clk_prepare_enable(ourport->clk);
if (ret) {
pr_err("uart: clock failed to prepare+enable: %d\n", ret);
clk_put(ourport->clk);
goto err;
}
/* Keep all interrupts masked and cleared */
if (s3c24xx_serial_has_interrupt_mask(port)) {
wr_regl(port, S3C64XX_UINTM, 0xf);
wr_regl(port, S3C64XX_UINTP, 0xf);
wr_regl(port, S3C64XX_UINTSP, 0xf);
}
dbg("port: map=%pa, mem=%p, irq=%d (%d,%d), clock=%u\n",
&port->mapbase, port->membase, port->irq,
ourport->rx_irq, ourport->tx_irq, port->uartclk);
/* reset the fifos (and setup the uart) */
s3c24xx_serial_resetport(port, cfg);
return 0;
err:
port->mapbase = 0;
return ret;
}
这里我们看一下串口的中断申请在那个函数里。
static struct uart_ops s3c24xx_serial_ops = {
.pm = s3c24xx_serial_pm,
.tx_empty = s3c24xx_serial_tx_empty,
.get_mctrl = s3c24xx_serial_get_mctrl,
.set_mctrl = s3c24xx_serial_set_mctrl,
.stop_tx = s3c24xx_serial_stop_tx,
.start_tx = s3c24xx_serial_start_tx,
.stop_rx = s3c24xx_serial_stop_rx,
.break_ctl = s3c24xx_serial_break_ctl,
.startup = s3c24xx_serial_startup,
.shutdown = s3c24xx_serial_shutdown,
.set_termios = s3c24xx_serial_set_termios,
.type = s3c24xx_serial_type,
.release_port = s3c24xx_serial_release_port,
.request_port = s3c24xx_serial_request_port,
.config_port = s3c24xx_serial_config_port,
.verify_port = s3c24xx_serial_verify_port,
#if defined(CONFIG_SERIAL_SAMSUNG_CONSOLE) && defined(CONFIG_CONSOLE_POLL)
.poll_get_char = s3c24xx_serial_get_poll_char,
.poll_put_char = s3c24xx_serial_put_poll_char,
#endif
};
static int s3c24xx_serial_startup(struct uart_port *port)
{
struct s3c24xx_uart_port *ourport = to_ourport(port);
int ret;
dbg("s3c24xx_serial_startup: port=%p (%08llx,%p)\n",
port, (unsigned long long)port->mapbase, port->membase);
rx_enabled(port) = 1;
ret = request_irq(ourport->rx_irq, s3c24xx_serial_rx_chars, 0,
s3c24xx_serial_portname(port), ourport);
if (ret != 0) {
dev_err(port->dev, "cannot get irq %d\n", ourport->rx_irq);
return ret;
}
ourport->rx_claimed = 1;
dbg("requesting tx irq...\n");
tx_enabled(port) = 1;
ret = request_irq(ourport->tx_irq, s3c24xx_serial_tx_chars, 0,
s3c24xx_serial_portname(port), ourport);
if (ret) {
dev_err(port->dev, "cannot get irq %d\n", ourport->tx_irq);
goto err;
}
ourport->tx_claimed = 1;
dbg("s3c24xx_serial_startup ok\n");
/* the port reset code should have done the correct
* register setup for the port controls */
return ret;
err:
s3c24xx_serial_shutdown(port);
return ret;
}
上面我们已经看到了发生和中断接收函数了，具体的细节就不再描述。
三、串口驱动的注册
if (!s3c24xx_uart_drv.state) {
ret = uart_register_driver(&s3c24xx_uart_drv);
if (ret < 0) {
pr_err("Failed to register Samsung UART driver\n");
return ret;
}
}
串口在linux系统中属于tty设备，tty设备是从古老的纸带打印机流传下来的。当时的输入，输出都是依靠纸带来传输。
后面有了串口之后，输入输出就都通过串口来传输。当然后面又有了新的显示器，键盘之类作为新的输入输出设备。
/**
* uart_register_driver - register a driver with the uart core layer
* @drv: low level driver structure
*
* Register a uart driver with the core driver. We in turn register
* with the tty layer, and initialise the core driver per-port state.
*
* We have a proc file in /proc/tty/driver which is named after the
* normal driver.
*
* drv->port should be NULL, and the per-port structures should be
* registered using uart_add_one_port after this call has succeeded.
*/
int uart_register_driver(struct uart_driver *drv)
{
struct tty_driver *normal;
int i, retval;
BUG_ON(drv->state);
/*
* Maybe we should be using a slab cache for this, especially if
* we have a large number of ports to handle.
*/
drv->state = kcalloc(drv->nr, sizeof(struct uart_state), GFP_KERNEL);
if (!drv->state)
goto out;
normal = alloc_tty_driver(drv->nr);
if (!normal)
goto out_kfree;
drv->tty_driver = normal;
normal->driver_name = drv->driver_name;
normal->name = drv->dev_name;
normal->major = drv->major;
normal->minor_start = drv->minor;
normal->type = TTY_DRIVER_TYPE_SERIAL;
normal->subtype = SERIAL_TYPE_NORMAL;
normal->init_termios = tty_std_termios;
normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;
normal->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
normal->driver_state = drv;
tty_set_operations(normal, &uart_ops);
/*
* Initialise the UART state(s).
*/
for (i = 0; i < drv->nr; i++) {
struct uart_state *state = drv->state + i;
struct tty_port *port = &state->port;
tty_port_init(port);
port->ops = &uart_port_ops;
}
retval = tty_register_driver(normal);
if (retval >= 0)
return retval;
for (i = 0; i < drv->nr; i++)
tty_port_destroy(&drv->state[i].port);
put_tty_driver(normal);
out_kfree:
kfree(drv->state);
out:
return -ENOMEM;
}这个函数是通过serial_core来内核帮我们定义好的，可以看到，主要做三件事，申请tty设备，初始化tty设备，注册tty设备。
这里不详细说了，后面驱动高级专题中，会和usb，tty，tcp/ip之类再详细开专题分析。
四、串口增加端口，其实就是注册console驱动。
dbg("%s: adding port\n", __func__);
uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);
platform_set_drvdata(pdev, &ourport->port);
/**
* uart_add_one_port - attach a driver-defined port structure
* @drv: pointer to the uart low level driver structure for this port
* @uport: uart port structure to use for this port.
*
* This allows the driver to register its own uart_port structure
* with the core driver. The main purpose is to allow the low
* level uart drivers to expand uart_port, rather than having yet
* more levels of structures.
*/
int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
{
struct uart_state *state;
struct tty_port *port;
int ret = 0;
struct device *tty_dev;
int num_groups;
BUG_ON(in_interrupt());
if (uport->line >= drv->nr)
return -EINVAL;
state = drv->state + uport->line;
port = &state->port;
mutex_lock(&port_mutex);
mutex_lock(&port->mutex);
if (state->uart_port) {
ret = -EINVAL;
goto out;
}
/* Link the port to the driver state table and vice versa */
atomic_set(&state->refcount, 1);
init_waitqueue_head(&state->remove_wait);
state->uart_port = uport;
uport->state = state;
state->pm_state = UART_PM_STATE_UNDEFINED;
uport->cons = drv->cons;
uport->minor = drv->tty_driver->minor_start + uport->line;
uport->name = kasprintf(GFP_KERNEL, "%s%d", drv->dev_name,
drv->tty_driver->name_base + uport->line);
if (!uport->name) {
ret = -ENOMEM;
goto out;
}
/*
* If this port is a console, then the spinlock is already
* initialised.
*/
if (!(uart_console(uport) && (uport->cons->flags & CON_ENABLED))) {
spin_lock_init(&uport->lock);
lockdep_set_class(&uport->lock, &port_lock_key);
}
if (uport->cons && uport->dev)
of_console_check(uport->dev->of_node, uport->cons->name, uport->line);
uart_configure_port(drv, state, uport);
port->console = uart_console(uport);
num_groups = 2;
if (uport->attr_group)
num_groups++;
uport->tty_groups = kcalloc(num_groups, sizeof(*uport->tty_groups),
GFP_KERNEL);
if (!uport->tty_groups) {
ret = -ENOMEM;
goto out;
}
uport->tty_groups[0] = &tty_dev_attr_group;
if (uport->attr_group)
uport->tty_groups[1] = uport->attr_group;
/*
* Register the port whether it's detected or not. This allows
* setserial to be used to alter this port's parameters.
*/
tty_dev = tty_port_register_device_attr_serdev(port, drv->tty_driver,
uport->line, uport->dev, port, uport->tty_groups);
if (likely(!IS_ERR(tty_dev))) {
device_set_wakeup_capable(tty_dev, 1);
} else {
dev_err(uport->dev, "Cannot register tty device on line %d\n",
uport->line);
}
/*
* Ensure UPF_DEAD is not set.
*/
uport->flags &= ~UPF_DEAD;
out:
mutex_unlock(&port->mutex);
mutex_unlock(&port_mutex);
return ret;
}上面就是注册端口了，这里要注意，端口是在uart_register_driver申请和创建的，地址在status里面。
接下来就是调用这个串口配置这个端口了
uart_configure_port(drv, state, uport);
static void
uart_configure_port(struct uart_driver *drv, struct uart_state *state,
struct uart_port *port)
{
unsigned int flags;
/*
* If there isn't a port here, don't do anything further.
*/
if (!port->iobase && !port->mapbase && !port->membase)
return;
/*
* Now do the auto configuration stuff. Note that config_port
* is expected to claim the resources and map the port for us.
*/
flags = 0;
if (port->flags & UPF_AUTO_IRQ)
flags |= UART_CONFIG_IRQ;
if (port->flags & UPF_BOOT_AUTOCONF) {
if (!(port->flags & UPF_FIXED_TYPE)) {
port->type = PORT_UNKNOWN;
flags |= UART_CONFIG_TYPE;
}
port->ops->config_port(port, flags);
}
if (port->type != PORT_UNKNOWN) {
unsigned long flags;
uart_report_port(drv, port);
/* Power up port for set_mctrl() */
uart_change_pm(state, UART_PM_STATE_ON);
/*
* Ensure that the modem control lines are de-activated.
* keep the DTR setting that is set in uart_set_options()
* We probably don't need a spinlock around this, but
*/
spin_lock_irqsave(&port->lock, flags);
port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR);
spin_unlock_irqrestore(&port->lock, flags);
/*
* If this driver supports console, and it hasn't been
* successfully registered yet, try to re-register it.
* It may be that the port was not available.
*/
if (port->cons && !(port->cons->flags & CON_ENABLED))
register_console(port->cons);
/*
* Power down all ports by default, except the
* console if we have one.
*/
if (!uart_console(port))
uart_change_pm(state, UART_PM_STATE_OFF);
}
}
配置端口主要还是注册console
register_console(port->cons);上面我们注意下面这个函数，会打印一些调试信息
uart_report_port(drv, port);
static inline void
uart_report_port(struct uart_driver *drv, struct uart_port *port)
{
char address[64];
switch (port->iotype) {
case UPIO_PORT:
snprintf(address, sizeof(address), "I/O 0x%lx", port->iobase);
break;
case UPIO_HUB6:
snprintf(address, sizeof(address),
"I/O 0x%lx offset 0x%x", port->iobase, port->hub6);
break;
case UPIO_MEM:
case UPIO_MEM16:
case UPIO_MEM32:
case UPIO_MEM32BE:
case UPIO_AU:
case UPIO_TSI:
snprintf(address, sizeof(address),
"MMIO 0x%llx", (unsigned long long)port->mapbase);
break;
default:
strlcpy(address, "*unknown*", sizeof(address));
break;
}
pr_info("%s%s%s at %s (irq = %d, base_baud = %d) is a %s\n",
port->dev ? dev_name(port->dev) : "",
port->dev ? ": " : "",
port->name,
address, port->irq, port->uartclk / 16, uart_type(port));
}
具体的如下，可以对比着看
/*
* The console driver calls this routine during kernel initialization
* to register the console printing procedure with printk() and to
* print any messages that were printed by the kernel before the
* console driver was initialized.
*
* This can happen pretty early during the boot process (because of
* early_printk) - sometimes before setup_arch() completes - be careful
* of what kernel features are used - they may not be initialised yet.
*
* There are two types of consoles - bootconsoles (early_printk) and
* "real" consoles (everything which is not a bootconsole) which are
* handled differently.
* - Any number of bootconsoles can be registered at any time.
* - As soon as a "real" console is registered, all bootconsoles
* will be unregistered automatically.
* - Once a "real" console is registered, any attempt to register a
* bootconsoles will be rejected
*/
void register_console(struct console *newcon)
{
int i;
unsigned long flags;
struct console *bcon = NULL;
struct console_cmdline *c;
static bool has_preferred;
if (console_drivers)
for_each_console(bcon)
if (WARN(bcon == newcon,
"console '%s%d' already registered\n",
bcon->name, bcon->index))
return;
/*
* before we register a new CON_BOOT console, make sure we don't
* already have a valid console
*/
if (console_drivers && newcon->flags & CON_BOOT) {
/* find the last or real console */
for_each_console(bcon) {
if (!(bcon->flags & CON_BOOT)) {
pr_info("Too late to register bootconsole %s%d\n",
newcon->name, newcon->index);
return;
}
}
}
if (console_drivers && console_drivers->flags & CON_BOOT)
bcon = console_drivers;
if (!has_preferred || bcon || !console_drivers)
has_preferred = preferred_console >= 0;
/*
* See if we want to use this console driver. If we
* didn't select a console we take the first one
* that registers here.
*/
if (!has_preferred) {
if (newcon->index < 0)
newcon->index = 0;
if (newcon->setup == NULL ||
newcon->setup(newcon, NULL) == 0) {
newcon->flags |= CON_ENABLED;
if (newcon->device) {
newcon->flags |= CON_CONSDEV;
has_preferred = true;
}
}
}
/*
* See if this console matches one we selected on
* the command line.
*/
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++) {
if (!newcon->match ||
newcon->match(newcon, c->name, c->index, c->options) != 0) {
/* default matching */
BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
if (strcmp(c->name, newcon->name) != 0)
continue;
if (newcon->index >= 0 &&
newcon->index != c->index)
continue;
if (newcon->index < 0)
newcon->index = c->index;
if (_braille_register_console(newcon, c))
return;
if (newcon->setup &&
newcon->setup(newcon, c->options) != 0)
break;
}
newcon->flags |= CON_ENABLED;
if (i == preferred_console) {
newcon->flags |= CON_CONSDEV;
has_preferred = true;
}
break;
}
if (!(newcon->flags & CON_ENABLED))
return;
/*
* If we have a bootconsole, and are switching to a real console,
* don't print everything out again, since when the boot console, and
* the real console are the same physical device, it's annoying to
* see the beginning boot messages twice
*/
if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
newcon->flags &= ~CON_PRINTBUFFER;
/*
* Put this console in the list - keep the
* preferred driver at the head of the list.
*/
console_lock();
if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
newcon->next = console_drivers;
console_drivers = newcon;
if (newcon->next)
newcon->next->flags &= ~CON_CONSDEV;
} else {
newcon->next = console_drivers->next;
console_drivers->next = newcon;
}
if (newcon->flags & CON_EXTENDED)
if (!nr_ext_console_drivers++)
pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
if (newcon->flags & CON_PRINTBUFFER) {
/*
* console_unlock(); will print out the buffered messages
* for us.
*/
logbuf_lock_irqsave(flags);
console_seq = syslog_seq;
console_idx = syslog_idx;
logbuf_unlock_irqrestore(flags);
/*
* We're about to replay the log buffer. Only do this to the
* just-registered console to avoid excessive message spam to
* the already-registered consoles.
*/
exclusive_console = newcon;
}
console_unlock();
console_sysfs_notify();
/*
* By unregistering the bootconsoles after we enable the real console
* we get the "console xxx enabled" message on all the consoles -
* boot consoles, real consoles, etc - this is to ensure that end
* users know there might be something in the kernel's log buffer that
* went to the bootconsole (that they do not see on the real console)
*/
pr_info("%sconsole [%s%d] enabled\n",
(newcon->flags & CON_BOOT) ? "boot" : "" ,
newcon->name, newcon->index);
if (bcon &&
((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
!keep_bootcon) {
/* We need to iterate through all boot consoles, to make
* sure we print everything out, before we unregister them.
*/
for_each_console(bcon)
if (bcon->flags & CON_BOOT)
unregister_console(bcon);
}
}注册console，其实就是把console使用链表方式next连接起来。
这就回到我们上一节的了，把注册的这个console和上节，uboot通过cmdline传过来的那些console和串口注册的做比较，如果名字和index都相同的话，则把这个串口表示使能CON_ENABLED，后面使用printk或printf的时候，就会调用使能的console打印信息。
#define MAX_CMDLINECONSOLES 8
static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
这里我们看一下细节，
在串口配置之前是要执行上面这个函数的，因为我们就是设备树传参的
if (uport->cons && uport->dev)
of_console_check(uport->dev->of_node, uport->cons->name, uport->line);
uart_configure_port(drv, state, uport);
/**
* of_console_check() - Test and setup console for DT setup
* @dn - Pointer to device node
* @name - Name to use for preferred console without index. ex. "ttyS"
* @index - Index to use for preferred console.
*
* Check if the given device node matches the stdout-path property in the
* /chosen node. If it does then register it as the preferred console and return
* TRUE. Otherwise return FALSE.
*/
bool of_console_check(struct device_node *dn, char *name, int index)
{
if (!dn || dn != of_stdout || console_set_on_cmdline)
return false;
/*
* XXX: cast `options' to char pointer to suppress complication
* warnings: printk, UART and console drivers expect char pointer.
*/
return !add_preferred_console(name, index, (char *)of_stdout_options);
}
/**
* add_preferred_console - add a device to the list of preferred consoles.
* @name: device name
* @idx: device index
* @options: options for this console
*
* The last preferred console added will be used for kernel messages
* and stdin/out/err for init. Normally this is used by console_setup
* above to handle user-supplied console arguments; however it can also
* be used by arch-specific code either to override the user or more
* commonly to provide a default console (ie from PROM variables) when
* the user has not supplied one.
*/
int add_preferred_console(char *name, int idx, char *options)
{
return __add_preferred_console(name, idx, options, NULL);
}
static int preferred_console = -1;
static int __add_preferred_console(char *name, int idx, char *options,
char *brl_options)
{
struct console_cmdline *c;
int i;
/*
* See if this tty is not yet registered, and
* if we have a slot free.
*/
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++) {
if (strcmp(c->name, name) == 0 && c->index == idx) {
if (!brl_options)
preferred_console = i;
return 0;
}
}
if (i == MAX_CMDLINECONSOLES)
return -E2BIG;
if (!brl_options)
preferred_console = i;
strlcpy(c->name, name, sizeof(c->name));
c->options = options;
braille_set_options(c, brl_options);
c->index = idx;
return 0;
}
可以看到这里是要判断的，只有名字以及port->line和console_cmdline[x].index匹配上，preferred_console 不为-1，而是和console_cmdline匹配上的下标值
比如我们uboot传的值是"console = ttySAC2"，所以ttySAC0匹配不成功，ttySAC2才能成功。
这里我们主要分析下面这个
void register_console(struct console *newcon)
{
......
if (!has_preferred || bcon || !console_drivers)
has_preferred = preferred_console >= 0;
/*
* See if we want to use this console driver. If we
* didn't select a console we take the first one
* that registers here.
*/
if (!has_preferred) {
if (newcon->index < 0)
newcon->index = 0;
if (newcon->setup == NULL ||
newcon->setup(newcon, NULL) == 0) {
newcon->flags |= CON_ENABLED;
if (newcon->device) {
newcon->flags |= CON_CONSDEV;
has_preferred = true;
}
}
}
/*
* See if this console matches one we selected on
* the command line.
*/
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++) {
if (!newcon->match ||
newcon->match(newcon, c->name, c->index, c->options) != 0) {
/* default matching */
BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
if (strcmp(c->name, newcon->name) != 0)
continue;
if (newcon->index >= 0 &&
newcon->index != c->index)
continue;
if (newcon->index < 0)
newcon->index = c->index;
if (_braille_register_console(newcon, c))
return;
if (newcon->setup &&
newcon->setup(newcon, c->options) != 0)
break;
}
newcon->flags |= CON_ENABLED;
if (i == preferred_console) {
newcon->flags |= CON_CONSDEV;
has_preferred = true;
}
break;
}
......
}
上面这个有三种情况，ttySAC0或1，ttySAC2，ttySAC3
第一种
从上向下走，
if (!has_preferred || bcon || !console_drivers)
has_preferred = preferred_console >= 0;
has_preferred 为 0
接下来执行下面这个，index会为0
*/
if (!has_preferred) {
if (newcon->index < 0)
newcon->index = 0;
if (newcon->setup == NULL ||
newcon->setup(newcon, NULL) == 0) {
newcon->flags |= CON_ENABLED;
if (newcon->device) {
newcon->flags |= CON_CONSDEV;
has_preferred = true;
}
}
}接下来执行下面这个，因为index为0，所以
/*
* See if this console matches one we selected on
* the command line.
*/
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++) {
if (!newcon->match ||
newcon->match(newcon, c->name, c->index, c->options) != 0) {
/* default matching */
BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
if (strcmp(c->name, newcon->name) != 0)
continue;
if (newcon->index >= 0 &&
newcon->index != c->index)
continue; //在这里重新遍历下一个,而因为没有下一个c-name[0]为空而跳出
if (newcon->index < 0)
newcon->index = c->index;
if (_braille_register_console(newcon, c))
return;
if (newcon->setup &&
newcon->setup(newcon, c->options) != 0)
break;
}
newcon->flags |= CON_ENABLED;
if (i == preferred_console) {
newcon->flags |= CON_CONSDEV;
has_preferred = true;
}
break;
}最后因为没使能而跳出整个函数
if (!(newcon->flags & CON_ENABLED))
return;
第二种
对于tyySAC2，
从上向下走，因为preferred_console 不为 -1
if (!has_preferred || bcon || !console_drivers)
has_preferred = preferred_console >= 0;
所以has_preferred 为 1
接下来不会执行这个
*/
if (!has_preferred) {
if (newcon->index < 0)
newcon->index = 0;
if (newcon->setup == NULL ||
newcon->setup(newcon, NULL) == 0) {
newcon->flags |= CON_ENABLED;
if (newcon->device) {
newcon->flags |= CON_CONSDEV;
has_preferred = true;
}
}
}
/*
* See if this console matches one we selected on
* the command line.
*/
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++) {
if (!newcon->match ||
newcon->match(newcon, c->name, c->index, c->options) != 0) {
/* default matching */
BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
if (strcmp(c->name, newcon->name) != 0)
continue;
if (newcon->index >= 0 &&
newcon->index != c->index)
continue;
if (newcon->index < 0) //-1小于0,所以newcon->index = c->index = 2
newcon->index = c->index;
if (_braille_register_console(newcon, c))
return;
if (newcon->setup &&
newcon->setup(newcon, c->options) != 0)
break;
}
/* 这里会执行 */
newcon->flags |= CON_ENABLED;
if (i == preferred_console) {
newcon->flags |= CON_CONSDEV; //这里也会执行
has_preferred = true;
}
break;
}
最后因为这个if进不去，也就不用退出
if (!(newcon->flags & CON_ENABLED))
return;
加入链表，进而打印enable信息
if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
newcon->next = console_drivers;
console_drivers = newcon;
if (newcon->next)
newcon->next->flags &= ~CON_CONSDEV;
} else {
newcon->next = console_drivers->next;
console_drivers->next = newcon;
}
......
pr_info("%sconsole [%s%d] enabled\n",
(newcon->flags & CON_BOOT) ? "boot" : "" ,
newcon->name, newcon->index);
对于第三种情况，我们回到配置
static void
uart_configure_port(struct uart_driver *drv, struct uart_state *state,
struct uart_port *port)
{
unsigned int flags;
/*
* If there isn't a port here, don't do anything further.
*/
if (!port->iobase && !port->mapbase && !port->membase)
return;
/*
* Now do the auto configuration stuff. Note that config_port
* is expected to claim the resources and map the port for us.
*/
flags = 0;
if (port->flags & UPF_AUTO_IRQ)
flags |= UART_CONFIG_IRQ;
if (port->flags & UPF_BOOT_AUTOCONF) {
if (!(port->flags & UPF_FIXED_TYPE)) {
port->type = PORT_UNKNOWN;
flags |= UART_CONFIG_TYPE;
}
port->ops->config_port(port, flags);
}
if (port->type != PORT_UNKNOWN) {
unsigned long flags;
uart_report_port(drv, port);
/* Power up port for set_mctrl() */
uart_change_pm(state, UART_PM_STATE_ON);
/*
* Ensure that the modem control lines are de-activated.
* keep the DTR setting that is set in uart_set_options()
* We probably don't need a spinlock around this, but
*/
spin_lock_irqsave(&port->lock, flags);
port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR);
spin_unlock_irqrestore(&port->lock, flags);
/*
* If this driver supports console, and it hasn't been
* successfully registered yet, try to re-register it.
* It may be that the port was not available.
*/
if (port->cons && !(port->cons->flags & CON_ENABLED))
register_console(port->cons);
/*
* Power down all ports by default, except the
* console if we have one.
*/
if (!uart_console(port))
uart_change_pm(state, UART_PM_STATE_OFF);
}
}虽然我们有四个串口
#define __PORT_LOCK_UNLOCKED(i) \
__SPIN_LOCK_UNLOCKED(s3c24xx_serial_ports[i].port.lock)
static struct s3c24xx_uart_port
s3c24xx_serial_ports[CONFIG_SERIAL_SAMSUNG_UARTS] = {
[0] = {
.port = {
.lock = __PORT_LOCK_UNLOCKED(0),
.iotype = UPIO_MEM,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 0,
}
},
[1] = {
.port = {
.lock = __PORT_LOCK_UNLOCKED(1),
.iotype = UPIO_MEM,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 1,
}
},
#if CONFIG_SERIAL_SAMSUNG_UARTS > 2
[2] = {
.port = {
.lock = __PORT_LOCK_UNLOCKED(2),
.iotype = UPIO_MEM,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 2,
}
},
#endif
#if CONFIG_SERIAL_SAMSUNG_UARTS > 3
[3] = {
.port = {
.lock = __PORT_LOCK_UNLOCKED(3),
.iotype = UPIO_MEM,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 3,
}
}
#endif
};
#undef __PORT_LOCK_UNLOCKED但只能有一个串口做console
static struct console s3c24xx_serial_console = {
.name = S3C24XX_SERIAL_NAME,
.device = uart_console_device,
.flags = CON_PRINTBUFFER,
.index = -1,
.write = s3c24xx_serial_console_write,
.setup = s3c24xx_serial_console_setup,
.data = &s3c24xx_uart_drv,
};
也就是在串口注册成功后，flag已经为CON_ENABLED，所以下面这个if进不去，所以串口3也是注册不了console的
/*
* If this driver supports console, and it hasn't been
* successfully registered yet, try to re-register it.
* It may be that the port was not available.
*/
if (port->cons && !(port->cons->flags & CON_ENABLED))
register_console(port->cons);
最后要说明一下，经过搜索，发现目前只有三星对串口驱动的名字叫做ttySACx
而其他厂家的有很多叫ttyS
所以设备树中，cmdline传参也是用和驱动名字一样的ttySx
