Operating procedures:
1, open: memory mapped device driver for opening
2, mmap: mapping the physical address space to the user
3, alt_read_word: reads a value from the specified register
4, alt_write_word: writing a value to the specified register
5, munmap: Clear memory map
6, close: close device driver
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Additional:
alt_setbits_word: setting a specified bit of a specified register
alt_setbits_word: setting the specified bit of the specified register is
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description link: https: //blog.csdn.net/smile_5me/article/details/81908506