Linux Device Driver Sum Up 2

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   :XJKZQ+ZSHYNTSX  +ZSHYNTSare for doing device i/o, to/from the i/o ports #include char inb(int port); char inw(int port); char outb(char val, int port); char outw(char val, int port);  +ZSHYNTSfor allocating small amounts of memory ( void *kmalloc(int size, int priority); void kfree_s(void *obj, int size); void kfree(void *obj); the priority is either :  GFP_KERNEL - for normal cases   GFP_ATOMIC - for allocating mem inside i
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            :XJKZQ + ZSHYNTSX     + ZSHYNTS  are for doing device i/o, to/from the i/o ports  #include <asm/io.h> char inb(int port);char inw(int port);char outb(char val, int port);char outw(char val, int port);    + ZSHYNTS  for allocating small amounts of memory (<4096 bytes)   #include <linux/malloc.h> void *kmalloc(int size, int priority);void kfree_s(void *obj, int size);void kfree(void *obj);the priority is either:    GFP _KERNEL - for normal cases     GFP _ATOMIC - for allocating mem inside interrupts     + ZSHYNTS  for allocating larger amounts of memory, such as device buffers   #include <linux/mm.h> void *vmalloc(long size);void vfree(void *obj);     #include <linux/kernel.h> int printk(char *fmt, ...);    to copy data to/from user space    #include <asm/segment.h> unsigned char get_fs_byte(const char *addr);unsigned short get_fs_word(const short *addr);unsigned long get_fs_long(const int *addr);void put_fs_byte(char val, char *addr);void put_fs_word(short val, short *addr);void put_fs_long(long val, int *addr);void memcpy_fromfs(void *to, void *from, unsigned long len);void memcpy_tofs(void *to, void *from, unsigned long len);    to set, clear, save and restore the interrupt enable flag   #include <asm/system.h> void sti();void cli();void save_flags(unsigned long flags);void restore_flags(unsigned long flags);     )W N[J W 'F XNHX     SJJI  YT \ W NYJ F S  NSYN F QN_ F YNTS  W TZYNSJ    In order that the device driver is correctly initialized whenthe operating system is booted, the xxx_init() routine must beexecuted.    To ensure this happens, add the following line to the end of thechr_drv_init() function in the/usr/src/linux/driver/char/mem.c file:  mem_start = xxx_init(mem_start); and resave the file back to disk.      xxx_init()  XMTZQI  KN W XY  H F QQ  register_chrdev()  YT  W JLNXYJ W  NYXJQK F SI F [TNI  IJ[NHJ  SZRGJ W  HTSYJSYNTS    7 JYZ W SX       NK  ST  TYMJ W  HM F W F HYJ W  IJ[NHJ  M F X  W JLNXYJ W JI \ NYM  YMJ  X F RJ  R FO T W  SZRGJ W      STS   NK  YMJ  H F QQ  K F NQX U W JXZR F GQ^  GJH F ZXJ F STYMJ W  HM F W F HYJ W  IJ[NHJ  M F X F Q W J F I^ F QQTH F YJI  YM F Y  R FO T W  SZRGJ W      SJJI  YT \ W NYJ  KZSHYNTSX  YT  KNQQ  NS  YMJ  XY W ZHY  KNQJDT U J W F YNTSX  XY W ZHYZ W J       :XNSL . SYJ WW Z U YX     SJJI  YT \ W NYJ F S  NSYJ WW Z U Y  XJ W [NHJ  W TZYNSJ .8 7     P JJ U NS  RNSI  YM F Y  NSYJ WW Z U YX F W J F X^SHM W TSTZX    YMJ^  H F S  THHZ W F Y F S^  YNRJ  void foo_interrupt(unsigned int irq, struct pt_reg *reg);    N WV  NX  YMJ  SZRGJ W  TK  YMJ  N WV \ MNHM  Y W NLLJ W JI  YMNX  W TZYNSJ    W JLX  NX F HT U ^  TK  YMJ (5 :  W JLNXYJ W X      5.   Kernel modules      from a source file mod.c of a kernel module, you compile it with gcc -Wall -O2-c mod.c      O nce you get the compiled mod.o , you can become root and install it to arunning kernel using insmod mod.o , and remove it from the kernel using rmmod mod .      M ost modules does not do a lot of things when being loaded. They just register some functions to the kernel, so that when the functionalities are needed, those
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