1.源码下载：
官网地址：https://www.kernel.org/
作者本次下载的内核版本为linux-5.1.7
2.input子系统：
由于最近工作中用到了keyadc，需要将用户按键上报给应用层，用到了input子系统，所以在此写一下对input子系统的理解，加深印象。
input子系统的头文件在linux-5.1.7/include/linux/input.h，我们看一下里面都有什么东西 。
1 /* 2 * Copyright (c) 1999-2002 Vojtech Pavlik 3 * 4 * This program is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 as published by 6 * the Free Software Foundation. 7 */ 8 #ifndef _INPUT_H 9 #define _INPUT_H 10 11 #include <linux/time.h> 12 #include <linux/list.h> 13 #include <uapi/linux/input.h> 14 /* Implementation details, userspace should not care about these */ 15 #define ABS_MT_FIRST ABS_MT_TOUCH_MAJOR 16 #define ABS_MT_LAST ABS_MT_TOOL_Y 17 18 /* 19 * In-kernel definitions. 20 */ 21 22 #include <linux/device.h> 23 #include <linux/fs.h> 24 #include <linux/timer.h> 25 #include <linux/mod_devicetable.h> 26 27 /** 28 * struct input_value - input value representation 29 * @type: type of value (EV_KEY, EV_ABS, etc) 30 * @code: the value code 31 * @value: the value 32 */ 33 struct input_value { 34 __u16 type; 35 __u16 code; 36 __s32 value; 37 }; 38 39 /** 40 * struct input_dev - represents an input device 41 * @name: name of the device 42 * @phys: physical path to the device in the system hierarchy 43 * @uniq: unique identification code for the device (if device has it) 44 * @id: id of the device (struct input_id) 45 * @propbit: bitmap of device properties and quirks 46 * @evbit: bitmap of types of events supported by the device (EV_KEY, 47 * EV_REL, etc.) 48 * @keybit: bitmap of keys/buttons this device has 49 * @relbit: bitmap of relative axes for the device 50 * @absbit: bitmap of absolute axes for the device 51 * @mscbit: bitmap of miscellaneous events supported by the device 52 * @ledbit: bitmap of leds present on the device 53 * @sndbit: bitmap of sound effects supported by the device 54 * @ffbit: bitmap of force feedback effects supported by the device 55 * @swbit: bitmap of switches present on the device 56 * @hint_events_per_packet: average number of events generated by the 57 * device in a packet (between EV_SYN/SYN_REPORT events). Used by 58 * event handlers to estimate size of the buffer needed to hold 59 * events. 60 * @keycodemax: size of keycode table 61 * @keycodesize: size of elements in keycode table 62 * @keycode: map of scancodes to keycodes for this device 63 * @getkeycode: optional legacy method to retrieve current keymap. 64 * @setkeycode: optional method to alter current keymap, used to implement 65 * sparse keymaps. If not supplied default mechanism will be used. 66 * The method is being called while holding event_lock and thus must 67 * not sleep 68 * @ff: force feedback structure associated with the device if device 69 * supports force feedback effects 70 * @repeat_key: stores key code of the last key pressed; used to implement 71 * software autorepeat 72 * @timer: timer for software autorepeat 73 * @rep: current values for autorepeat parameters (delay, rate) 74 * @mt: pointer to multitouch state 75 * @absinfo: array of &struct input_absinfo elements holding information 76 * about absolute axes (current value, min, max, flat, fuzz, 77 * resolution) 78 * @key: reflects current state of device's keys/buttons 79 * @led: reflects current state of device's LEDs 80 * @snd: reflects current state of sound effects 81 * @sw: reflects current state of device's switches 82 * @open: this method is called when the very first user calls 83 * input_open_device(). The driver must prepare the device 84 * to start generating events (start polling thread, 85 * request an IRQ, submit URB, etc.) 86 * @close: this method is called when the very last user calls 87 * input_close_device(). 88 * @flush: purges the device. Most commonly used to get rid of force 89 * feedback effects loaded into the device when disconnecting 90 * from it 91 * @event: event handler for events sent _to_ the device, like EV_LED 92 * or EV_SND. The device is expected to carry out the requested 93 * action (turn on a LED, play sound, etc.) The call is protected 94 * by @event_lock and must not sleep 95 * @grab: input handle that currently has the device grabbed (via 96 * EVIOCGRAB ioctl). When a handle grabs a device it becomes sole 97 * recipient for all input events coming from the device 98 * @event_lock: this spinlock is taken when input core receives 99 * and processes a new event for the device (in input_event()). 100 * Code that accesses and/or modifies parameters of a device 101 * (such as keymap or absmin, absmax, absfuzz, etc.) after device 102 * has been registered with input core must take this lock. 103 * @mutex: serializes calls to open(), close() and flush() methods 104 * @users: stores number of users (input handlers) that opened this 105 * device. It is used by input_open_device() and input_close_device() 106 * to make sure that dev->open() is only called when the first 107 * user opens device and dev->close() is called when the very 108 * last user closes the device 109 * @going_away: marks devices that are in a middle of unregistering and 110 * causes input_open_device*() fail with -ENODEV. 111 * @dev: driver model's view of this device 112 * @h_list: list of input handles associated with the device. When 113 * accessing the list dev->mutex must be held 114 * @node: used to place the device onto input_dev_list 115 * @num_vals: number of values queued in the current frame 116 * @max_vals: maximum number of values queued in a frame 117 * @vals: array of values queued in the current frame 118 * @devres_managed: indicates that devices is managed with devres framework 119 * and needs not be explicitly unregistered or freed. 120 */ 121 struct input_dev { 122 const char *name; 123 const char *phys; 124 const char *uniq; 125 struct input_id id; 126 127 unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)]; 128 129 unsigned long evbit[BITS_TO_LONGS(EV_CNT)]; 130 unsigned long keybit[BITS_TO_LONGS(KEY_CNT)]; 131 unsigned long relbit[BITS_TO_LONGS(REL_CNT)]; 132 unsigned long absbit[BITS_TO_LONGS(ABS_CNT)]; 133 unsigned long mscbit[BITS_TO_LONGS(MSC_CNT)]; 134 unsigned long ledbit[BITS_TO_LONGS(LED_CNT)]; 135 unsigned long sndbit[BITS_TO_LONGS(SND_CNT)]; 136 unsigned long ffbit[BITS_TO_LONGS(FF_CNT)]; 137 unsigned long swbit[BITS_TO_LONGS(SW_CNT)]; 138 139 unsigned int hint_events_per_packet; 140 141 unsigned int keycodemax; 142 unsigned int keycodesize; 143 void *keycode; 144 145 int (*setkeycode)(struct input_dev *dev, 146 const struct input_keymap_entry *ke, 147 unsigned int *old_keycode); 148 int (*getkeycode)(struct input_dev *dev, 149 struct input_keymap_entry *ke); 150 151 struct ff_device *ff; 152 153 unsigned int repeat_key; 154 struct timer_list timer; 155 156 int rep[REP_CNT]; 157 158 struct input_mt *mt; 159 160 struct input_absinfo *absinfo; 161 162 unsigned long key[BITS_TO_LONGS(KEY_CNT)]; 163 unsigned long led[BITS_TO_LONGS(LED_CNT)]; 164 unsigned long snd[BITS_TO_LONGS(SND_CNT)]; 165 unsigned long sw[BITS_TO_LONGS(SW_CNT)]; 166 167 int (*open)(struct input_dev *dev); 168 void (*close)(struct input_dev *dev); 169 int (*flush)(struct input_dev *dev, struct file *file); 170 int (*event)(struct input_dev *dev, unsigned int type, unsigned int code, int value); 171 172 struct input_handle __rcu *grab; 173 174 spinlock_t event_lock; 175 struct mutex mutex; 176 177 unsigned int users; 178 bool going_away; 179 180 struct device dev; 181 182 struct list_head h_list; 183 struct list_head node; 184 185 unsigned int num_vals; 186 unsigned int max_vals; 187 struct input_value *vals; 188 189 bool devres_managed; 190 }; 191 #define to_input_dev(d) container_of(d, struct input_dev, dev) 192 193 /* 194 * Verify that we are in sync with input_device_id mod_devicetable.h #defines 195 */ 196 197 #if EV_MAX != INPUT_DEVICE_ID_EV_MAX 198 #error "EV_MAX and INPUT_DEVICE_ID_EV_MAX do not match" 199 #endif 200 201 #if KEY_MIN_INTERESTING != INPUT_DEVICE_ID_KEY_MIN_INTERESTING 202 #error "KEY_MIN_INTERESTING and INPUT_DEVICE_ID_KEY_MIN_INTERESTING do not match" 203 #endif 204 205 #if KEY_MAX != INPUT_DEVICE_ID_KEY_MAX 206 #error "KEY_MAX and INPUT_DEVICE_ID_KEY_MAX do not match" 207 #endif 208 209 #if REL_MAX != INPUT_DEVICE_ID_REL_MAX 210 #error "REL_MAX and INPUT_DEVICE_ID_REL_MAX do not match" 211 #endif 212 213 #if ABS_MAX != INPUT_DEVICE_ID_ABS_MAX 214 #error "ABS_MAX and INPUT_DEVICE_ID_ABS_MAX do not match" 215 #endif 216 217 #if MSC_MAX != INPUT_DEVICE_ID_MSC_MAX 218 #error "MSC_MAX and INPUT_DEVICE_ID_MSC_MAX do not match" 219 #endif 220 221 #if LED_MAX != INPUT_DEVICE_ID_LED_MAX 222 #error "LED_MAX and INPUT_DEVICE_ID_LED_MAX do not match" 223 #endif 224 225 #if SND_MAX != INPUT_DEVICE_ID_SND_MAX 226 #error "SND_MAX and INPUT_DEVICE_ID_SND_MAX do not match" 227 #endif 228 229 #if FF_MAX != INPUT_DEVICE_ID_FF_MAX 230 #error "FF_MAX and INPUT_DEVICE_ID_FF_MAX do not match" 231 #endif 232 233 #if SW_MAX != INPUT_DEVICE_ID_SW_MAX 234 #error "SW_MAX and INPUT_DEVICE_ID_SW_MAX do not match" 235 #endif 236 237 #if INPUT_PROP_MAX != INPUT_DEVICE_ID_PROP_MAX 238 #error "INPUT_PROP_MAX and INPUT_DEVICE_ID_PROP_MAX do not match" 239 #endif 240 241 #define INPUT_DEVICE_ID_MATCH_DEVICE \ 242 (INPUT_DEVICE_ID_MATCH_BUS | INPUT_DEVICE_ID_MATCH_VENDOR | INPUT_DEVICE_ID_MATCH_PRODUCT) 243 #define INPUT_DEVICE_ID_MATCH_DEVICE_AND_VERSION \ 244 (INPUT_DEVICE_ID_MATCH_DEVICE | INPUT_DEVICE_ID_MATCH_VERSION) 245 246 struct input_handle; 247 248 /** 249 * struct input_handler - implements one of interfaces for input devices 250 * @private: driver-specific data 251 * @event: event handler. This method is being called by input core with 252 * interrupts disabled and dev->event_lock spinlock held and so 253 * it may not sleep 254 * @events: event sequence handler. This method is being called by 255 * input core with interrupts disabled and dev->event_lock 256 * spinlock held and so it may not sleep 257 * @filter: similar to @event; separates normal event handlers from 258 * "filters". 259 * @match: called after comparing device's id with handler's id_table 260 * to perform fine-grained matching between device and handler 261 * @connect: called when attaching a handler to an input device 262 * @disconnect: disconnects a handler from input device 263 * @start: starts handler for given handle. This function is called by 264 * input core right after connect() method and also when a process 265 * that "grabbed" a device releases it 266 * @legacy_minors: set to %true by drivers using legacy minor ranges 267 * @minor: beginning of range of 32 legacy minors for devices this driver 268 * can provide 269 * @name: name of the handler, to be shown in /proc/bus/input/handlers 270 * @id_table: pointer to a table of input_device_ids this driver can 271 * handle 272 * @h_list: list of input handles associated with the handler 273 * @node: for placing the driver onto input_handler_list 274 * 275 * Input handlers attach to input devices and create input handles. There 276 * are likely several handlers attached to any given input device at the 277 * same time. All of them will get their copy of input event generated by 278 * the device. 279 * 280 * The very same structure is used to implement input filters. Input core 281 * allows filters to run first and will not pass event to regular handlers 282 * if any of the filters indicate that the event should be filtered (by 283 * returning %true from their filter() method). 284 * 285 * Note that input core serializes calls to connect() and disconnect() 286 * methods. 287 */ 288 struct input_handler { 289 290 void *private; 291 292 void (*event)(struct input_handle *handle, unsigned int type, unsigned int code, int value); 293 void (*events)(struct input_handle *handle, 294 const struct input_value *vals, unsigned int count); 295 bool (*filter)(struct input_handle *handle, unsigned int type, unsigned int code, int value); 296 bool (*match)(struct input_handler *handler, struct input_dev *dev); 297 int (*connect)(struct input_handler *handler, struct input_dev *dev, const struct input_device_id *id); 298 void (*disconnect)(struct input_handle *handle); 299 void (*start)(struct input_handle *handle); 300 301 bool legacy_minors; 302 int minor; 303 const char *name; 304 305 const struct input_device_id *id_table; 306 307 struct list_head h_list; 308 struct list_head node; 309 }; 310 311 /** 312 * struct input_handle - links input device with an input handler 313 * @private: handler-specific data 314 * @open: counter showing whether the handle is 'open', i.e. should deliver 315 * events from its device 316 * @name: name given to the handle by handler that created it 317 * @dev: input device the handle is attached to 318 * @handler: handler that works with the device through this handle 319 * @d_node: used to put the handle on device's list of attached handles 320 * @h_node: used to put the handle on handler's list of handles from which 321 * it gets events 322 */ 323 struct input_handle { 324 325 void *private; 326 327 int open; 328 const char *name; 329 330 struct input_dev *dev; 331 struct input_handler *handler; 332 333 struct list_head d_node; 334 struct list_head h_node; 335 }; 336 337 struct input_dev __must_check *input_allocate_device(void); 338 struct input_dev __must_check *devm_input_allocate_device(struct device *); 339 void input_free_device(struct input_dev *dev); 340 341 static inline struct input_dev *input_get_device(struct input_dev *dev) 342 { 343 return dev ? to_input_dev(get_device(&dev->dev)) : NULL; 344 } 345 346 static inline void input_put_device(struct input_dev *dev) 347 { 348 if (dev) 349 put_device(&dev->dev); 350 } 351 352 static inline void *input_get_drvdata(struct input_dev *dev) 353 { 354 return dev_get_drvdata(&dev->dev); 355 } 356 357 static inline void input_set_drvdata(struct input_dev *dev, void *data) 358 { 359 dev_set_drvdata(&dev->dev, data); 360 } 361 362 int __must_check input_register_device(struct input_dev *); 363 void input_unregister_device(struct input_dev *); 364 365 void input_reset_device(struct input_dev *); 366 367 int __must_check input_register_handler(struct input_handler *); 368 void input_unregister_handler(struct input_handler *); 369 370 int __must_check input_get_new_minor(int legacy_base, unsigned int legacy_num, 371 bool allow_dynamic); 372 void input_free_minor(unsigned int minor); 373 374 int input_handler_for_each_handle(struct input_handler *, void *data, 375 int (*fn)(struct input_handle *, void *)); 376 377 int input_register_handle(struct input_handle *); 378 void input_unregister_handle(struct input_handle *); 379 380 int input_grab_device(struct input_handle *); 381 void input_release_device(struct input_handle *); 382 383 int input_open_device(struct input_handle *); 384 void input_close_device(struct input_handle *); 385 386 int input_flush_device(struct input_handle *handle, struct file *file); 387 388 void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value); 389 void input_inject_event(struct input_handle *handle, unsigned int type, unsigned int code, int value); 390 391 static inline void input_report_key(struct input_dev *dev, unsigned int code, int value) 392 { 393 input_event(dev, EV_KEY, code, !!value); 394 } 395 396 static inline void input_report_rel(struct input_dev *dev, unsigned int code, int value) 397 { 398 input_event(dev, EV_REL, code, value); 399 } 400 401 static inline void input_report_abs(struct input_dev *dev, unsigned int code, int value) 402 { 403 input_event(dev, EV_ABS, code, value); 404 } 405 406 static inline void input_report_ff_status(struct input_dev *dev, unsigned int code, int value) 407 { 408 input_event(dev, EV_FF_STATUS, code, value); 409 } 410 411 static inline void input_report_switch(struct input_dev *dev, unsigned int code, int value) 412 { 413 input_event(dev, EV_SW, code, !!value); 414 } 415 416 static inline void input_sync(struct input_dev *dev) 417 { 418 input_event(dev, EV_SYN, SYN_REPORT, 0); 419 } 420 421 static inline void input_mt_sync(struct input_dev *dev) 422 { 423 input_event(dev, EV_SYN, SYN_MT_REPORT, 0); 424 } 425 426 void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code); 427 428 /** 429 * input_set_events_per_packet - tell handlers about the driver event rate 430 * @dev: the input device used by the driver 431 * @n_events: the average number of events between calls to input_sync() 432 * 433 * If the event rate sent from a device is unusually large, use this 434 * function to set the expected event rate. This will allow handlers 435 * to set up an appropriate buffer size for the event stream, in order 436 * to minimize information loss. 437 */ 438 static inline void input_set_events_per_packet(struct input_dev *dev, int n_events) 439 { 440 dev->hint_events_per_packet = n_events; 441 } 442 443 void input_alloc_absinfo(struct input_dev *dev); 444 void input_set_abs_params(struct input_dev *dev, unsigned int axis, 445 int min, int max, int fuzz, int flat); 446 447 #define INPUT_GENERATE_ABS_ACCESSORS(_suffix, _item) \ 448 static inline int input_abs_get_##_suffix(struct input_dev *dev, \ 449 unsigned int axis) \ 450 { \ 451 return dev->absinfo ? dev->absinfo[axis]._item : 0; \ 452 } \ 453 \ 454 static inline void input_abs_set_##_suffix(struct input_dev *dev, \ 455 unsigned int axis, int val) \ 456 { \ 457 input_alloc_absinfo(dev); \ 458 if (dev->absinfo) \ 459 dev->absinfo[axis]._item = val; \ 460 } 461 462 INPUT_GENERATE_ABS_ACCESSORS(val, value) 463 INPUT_GENERATE_ABS_ACCESSORS(min, minimum) 464 INPUT_GENERATE_ABS_ACCESSORS(max, maximum) 465 INPUT_GENERATE_ABS_ACCESSORS(fuzz, fuzz) 466 INPUT_GENERATE_ABS_ACCESSORS(flat, flat) 467 INPUT_GENERATE_ABS_ACCESSORS(res, resolution) 468 469 int input_scancode_to_scalar(const struct input_keymap_entry *ke, 470 unsigned int *scancode); 471 472 int input_get_keycode(struct input_dev *dev, struct input_keymap_entry *ke); 473 int input_set_keycode(struct input_dev *dev, 474 const struct input_keymap_entry *ke); 475 476 bool input_match_device_id(const struct input_dev *dev, 477 const struct input_device_id *id); 478 479 void input_enable_softrepeat(struct input_dev *dev, int delay, int period); 480 481 extern struct class input_class; 482 483 /** 484 * struct ff_device - force-feedback part of an input device 485 * @upload: Called to upload an new effect into device 486 * @erase: Called to erase an effect from device 487 * @playback: Called to request device to start playing specified effect 488 * @set_gain: Called to set specified gain 489 * @set_autocenter: Called to auto-center device 490 * @destroy: called by input core when parent input device is being 491 * destroyed 492 * @private: driver-specific data, will be freed automatically 493 * @ffbit: bitmap of force feedback capabilities truly supported by 494 * device (not emulated like ones in input_dev->ffbit) 495 * @mutex: mutex for serializing access to the device 496 * @max_effects: maximum number of effects supported by device 497 * @effects: pointer to an array of effects currently loaded into device 498 * @effect_owners: array of effect owners; when file handle owning 499 * an effect gets closed the effect is automatically erased 500 * 501 * Every force-feedback device must implement upload() and playback() 502 * methods; erase() is optional. set_gain() and set_autocenter() need 503 * only be implemented if driver sets up FF_GAIN and FF_AUTOCENTER 504 * bits. 505 * 506 * Note that playback(), set_gain() and set_autocenter() are called with 507 * dev->event_lock spinlock held and interrupts off and thus may not 508 * sleep. 509 */ 510 struct ff_device { 511 int (*upload)(struct input_dev *dev, struct ff_effect *effect, 512 struct ff_effect *old); 513 int (*erase)(struct input_dev *dev, int effect_id); 514 515 int (*playback)(struct input_dev *dev, int effect_id, int value); 516 void (*set_gain)(struct input_dev *dev, u16 gain); 517 void (*set_autocenter)(struct input_dev *dev, u16 magnitude); 518 519 void (*destroy)(struct ff_device *); 520 521 void *private; 522 523 unsigned long ffbit[BITS_TO_LONGS(FF_CNT)]; 524 525 struct mutex mutex; 526 527 int max_effects; 528 struct ff_effect *effects; 529 struct file *effect_owners[]; 530 }; 531 532 int input_ff_create(struct input_dev *dev, unsigned int max_effects); 533 void input_ff_destroy(struct input_dev *dev); 534 535 int input_ff_event(struct input_dev *dev, unsigned int type, unsigned int code, int value); 536 537 int input_ff_upload(struct input_dev *dev, struct ff_effect *effect, struct file *file); 538 int input_ff_erase(struct input_dev *dev, int effect_id, struct file *file); 539 int input_ff_flush(struct input_dev *dev, struct file *file); 540 541 int input_ff_create_memless(struct input_dev *dev, void *data, 542 int (*play_effect)(struct input_dev *, void *, struct ff_effect *)); 543 544 #endif
这里面最重要的是struct input_dev这个结构体