9.1 Kernel Programming ???

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?9? ???? ???? ??
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? ?

• 9.1 Kernel Programming ???
• 9.1.1 Kernel Programming?
• 9.1.2 Kernel vs Application
• 9.1.3 Kernel programming ?? ??
• 9.1.4 Kernel Interface ??
• 9.2 System call ????
• 9.2.1 System call???
• 9.2.2 POSIX API? System calls
• 9.2.3 System call ?? ????
• 9.2.4 System call ?? ??
• 9.2.5 System call ??
• 9.3 Device Driver
• 9.3.1 Device Driver?
• 9.3.1 Device Driver? ??
• 9.3.3 Device Driver ??
• 9.3.4 ??? Driver ?????? ???
• 9.3.5 Makefile ???

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9.1 Kernel Programming ???

• Linux kernel core ?? ??
• Linux kernel ???? ??
• Linux kernel ?? ?????

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9.1.1 Kernel vs Application

• ?? ??
• Application Program ???? ????? ??
• Kernel ??????? ?? system call?? ???? ???? ????
  ?? ??? ??? ??

Application
Kernel
System call
Interrupt
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9.1.1 Kernel vs Application

• Library
• Kernel kernel?? export ?? ??? ??? ? ??.
• Application Program ?? library? link ?? ??? ?
  ??.
• Kernel mode vs User mode
• Kernel Program ?? ?? ????.
• Application Program user mode?? ???? ????? ??
  ???? ?? ???? ?? ???? ?? ??? ????.

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9.1.1 Kernel vs Application

• Address Space
• Application Program? Kernel Program? ?? ?? ???
  ???? ??? ???, ???? ??? ?? ?? address space? ???
  ??.

1 G byte
4 G byte
3 G byte
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9.1.1 Kernel vs Application

• Namespace pollution
• Application Program ?? ???? ??????? ? ??? ???
  ??? ???? ?? ??.
• Kernel Program ?? ???? ?? ??? ?? ????? ??? ???
  ??? ???? ??? ??? ??.

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9.1.2 Kernel programming ?? ??

• Library
• stdio.h ? ?? ?? ?????? ???? ?? ??? include???
  ???.
• ?? /usr/include/linux ? /usr/include/asm ??? ???
  ???? ?? include ??.
• Namespace pollution
• ?? ??? link?? ?? ?? ??? static?? ?? ?? ?? ???
  link? symbol? symbol table ??
• EXPORT_NO_SYMBOLS
• EXPORT_SYMBOL(name)
• ?? ??? ? ??? prefix? ?? ??.
• Ex sys_open()

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9.1.2 Kernel programming ?? ??

• Fault handling
• Kernel ? ???? ??? ?? ??? ??? ?? ??? ????? ???
  ???? ???? ??? ?????.
• ?? ?? ?? ??? ?? ?? ??? ???? ???? ??.
• Address space
• ??? ???? stack? ??? ???? ??, ???? ???? ??? ???
  ????? ? ??? ?????, recursion? ?? ???? ??? ????
  ??.
• Application ? data? ?? ?? ??(call by reference)
  ??? ??? ?? ??? ??. (? ???? ?? ?? ? ?? ??? ????.)

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9.1.2 Kernel programming ?? ??

• ??
• ???? ?? MMX ??? ??? ? ??.

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9.1.3 Kernel Interface ??

• ?? ??
• Kernel program? ???? library? ???? ??? kernel??
  export ?? ??? ?? ??? ? ??.
• Kernel interface ?? ??
• Kernel ?? ???? ?? ? kernel programming? ?? ????
  ??? ??? ?? ??? ? ??.
• Port I/O
• Interrupt
• Memory
• Synchronization
• Kernel message ??
• Device Driver register

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9.1.3 Kernel Interface ??

• I/O device ? data? ?? ?? ?? ???
• unsigned inb(unsigned port)
• Port?? 1byte? ???.
• unsigned inw(unsigned port)
• Port?? 2byte? ???.
• unsigned inl(unsigned port)
• Port?? 4byte? ???.
• unsigned outb(char value, unsigned port)
• Port? 1byte value? ??.
• unsigned outw(short int value, unsigned port)
• Port? 2byte value? ??.
• unsigned outl(long int value, unsigned port)
• Port? 4byte value? ??.

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9.1.3 Kernel Interface ??

• I/O device ? data? ?? ?? ?? ???
• void insb(unsigned port, void addr, unsigned
  long count)
• Port?? count bytes? ??? ???? addr ???? ??
• void insw(unsigned port, void addr, unsigned
  long count)
• Port?? 16bit count ?? ??? ???? addr ???? ??
• void insl(unsigned port, void addr, unsigned
  long count)
• Port?? 32bit count ?? ??? ???? addr ???? ??
• void outsb(unsigned port, void addr, unsigned
  long count)
• Memory? addr?? ???? count bytes? ??? port? ??.
• void outsw(unsigned port, void addr, unsigned
  long count)
• Memory? addr?? ???? count 16bit? ??? port? ??.
• void outsl(unsigned port, void addr, unsigned
  long count)
• Memory? addr?? ???? count 32bit? ??? port? ??.

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9.1.3 Kernel Interface ??

• I/O device ? data? ?? ?? ?? ???
• Pausing I/O
• ???? ?? ??? device?? ??? ? ?? ??? ??? ? ?? ???
  ??? ??? ? ?? ??? ? ? ??.
• ?? ??? ??? ?? ?? _p ? ?? ??? ??? ???? ??.
• ?) inb() ??? ?? inb_p()

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9.1.3 Kernel Interface ??

• ????? ?? ? ??? ?? ??(or ???)
• cli()/sti()
• clear/set interrupt enable
• save_flags(unsigned long flag),
  restore_flags(unsigned long flag)
• status register? ??? ???? ??
• save_flags(), restore_flags() ? ???? ?? ?? ??? ??
  ??? ??. flag? ?? ??? pass??? ???.
• int requst_irq(unsigned int irq, void
  (handler)(int),unsigned long flags, const char
  device)
• ????? IRQ? ????, ? IRQ? ?? interrupt handler?
  install

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9.1.3 Kernel Interface ??

• ????? ?? ? ??? ?? ??(or ???)
• void free_irq(unsigned int irq)
• request_irq()?? ??? irq? ???

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9.1.3 Kernel Interface ??

• Kernel?? ?? ???? ??? ? ???? ???
• void kmalloc(unsigned int len, int priority)
• ?? ??? ??. 128131056byte?? ??
• priorityGFP_BUFFER, GFP_ATOMIC, GFP_USER,
  GFP_KERNEL
• ????? ???? ???? ????.
• void kfree(void obj)
• kmalloc()?? ?? ?? ?? ???? ??

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9.1.3 Kernel Interface ??

• Kernel?? ?? ???? ??? ? ???? ???
• void vmalloc(unsigned int len)
• ?? ??? ??
• ?? ?? ??
• ?? ?? ???? ???? ??? ??? ??
• void vmfree(void addr)
• vmalloc()?? ?? ?? ?? ???? ??

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9.1.3 Kernel Interface ??

• ??? ??? ???? ??? ???? ???? ?? ??
• unsigned long copy_from_user(void to, const void
  from, unsigned long n)
• ??? ?????? n byte?? data ??.
• unsigned long copy_to_user(void to, const void
  from, unsigned long n)
• ??? ?? ??? n byte?? data ??
• void memset(void s, char c, sizt_t count)
• ??? s? c? count?? ??
• put_user(datum,ptr) / get_user(ptr)
• ??? ??? datum? ????? ???? ?? ???

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9.1.3 Kernel Interface ??

• ???
• void sleep_on(struct wait_queue q)
• q? ??? event? sleep??, uninterruptible
• void sleep_in_interruptible(struct wait_queue
  q)
• q? ??? event? sleep??, interruptible
• void wake_up(struct wait_queue q)
• sleep_on(q)? ?? sleep? task? wakeup
• void wake_up_interruptible(struct wait_queuq q)
• sleep_on_interruptible(q)? ?? sleep? task? wakeup

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9.1.3 Kernel Interface ??

• Standard out ?? ???? ???? ?? ??
• printk(const char fmt, .)
• printf? ?? ??
• printk(LOG_LEVEL_ message)
• LOG_LEVELKERN_EMERG, KERN_ALERT,
  KERN_ERR,KERN_WARNING, KER_INFO, KERN_DEBUG
• ?
• printk(lt1gtHello, World)
• printk(KERN_WARNINGwarning \n)

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9.1.3 Kernel Interface ??

• Device Driver register
• int register_xxxdev
• (unsigned int major, const char name,struct
  file_operations fops)
• character/block driver? xxxdevmajor? ??
• xxxblk/chr
• int unregister_xxxdev(unsigned int major, const
  char name)
• xxxdevsmajor? ??? ?? device driver? ??
• int register_netdev(const char name)
• int unregister_netdev(const char name)
• MAJOR(kdev_t dev)/MINOR(kdev_t dev)
• ????dev??? major/minor ??? ??

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9.2 System Call
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9.2.1 Whats System Calls?

• user mode process? kernel ?? interface
• user mode process? ????? kernel ??? ????? ??? ?
  ??. ? kernel? ???? ? hardware ? ?? ?? ??
• user mode process? kernel? ??? ?? ???? ?? ???
  ????? hardware? ???? hardware? ???? ???? kernel
  ?? communication channel? ??.

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9.2.2POSIX API System calls

• POSIX API (Application Programming Interface)
• ??? ????? ??? ?? ?? ??? ?? ???? ?????.
• application? ???? ? ???? ??? ?? ??? ??? ???? ???
  ??? ?.
• ??? ?? ?? ?? ???? ?? ????? porting ?? ?? ?? ?? ??
  ?? ??.
• open(), close(), read(), write() ?
• System Call
• ????? ????? ?? ??? ???? ???? ?
• Linux??? POSIX API? ???? library ?? ??? system
  call ??? ?????? system call? ????.

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9.2.2POSIX API System calls

• ?gt ?????? ? open() ?? ? ? sys_open() ??
• (POSIX API) (??? ?)

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9.2.3 System Call ?? ????

• ??
• ?? kernel?? ???? ?? service? user application? ??
  ? ??? System Call ? ???.
• ??
• ?? ??
• System Call ?? ??
• System Call ?? ??? ??
• System Call ?? ?? ??
• Kernel ??? ? target board? ??
• user application ??
• ?? ??? System Call? ???? application ??
• library ??(??? ??? ?? ???.)
• Ramdisk? ????? target board? ??

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9.2.3 System Call ?? ????

• ??
• /PXA270/kernel/linux-2.6.11-h270-tku_v1.1/ ?
  target system? kernel source code? ??.
• ? ????? ???? ???? kernel? ????.

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9.2.3 System Call ?? ????

• System Call ?? ??
• Linux ??? ???? ?? ??? ??? ?? ??? ??? ??? ??.
• kernel/include/asm-arm/unistd.h ? ? ??? ??? ??
  ??? ?? ?? ??.
• ? ?? ??? system call? ???? ?? ??
• kernel/include/asm-arm/unistd.h ??? vi? ??.

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9.2.3 System Call ?? ????

• ??? ?? ??? System Call? ????? ??? ? ???? ???.
• unistd.h ??? ? ??? ?? ?? system call ? 280 ?? ??
  ?? ??? ? ??. ??? system call ? ? ??? ??281???
  ????.
• __NR_? System Call ????? ???? ????? ? ??
  hybuscall? ??? System Call ?? ??? ????.
• (sys_hybuscall ? ??? ?? ?? ? ??.)

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9.2.3 System Call ?? ????

• System Call ???? System Call ?? ?? ??
• kernel/arch/arm/kernel/entry-comm.S ?
  sys_call_table??? entry? ???? ??.
• sys_call_table?? system call ????? ?? ???? ???? ?
  ???? unistd.h? ?? ???? system call ??? ???? ??
  ????.
• ? sys_call_table? ??? System Call ???? ??
• entry-comm.S ??? vi? ??.

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9.2.3 System Call ?? ????

• entry-comm.S ?? ??? ?? ??? ??? ? ??.
• ENTRY(sys_call_table) ??? calls.S? include?? ??.
  vi? ??? ?? calls.S? ?? ??.

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9.2.3 System Call ?? ????

• calls.S ? ??? ??? ??.
• ltkernelgt/arch/arm/kernel

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9.2.3 System Call ?? ????

• ??? ?? ??? System Call ????? ??? ? ?? ?? ???.

unistd.h? ??? ??? ??
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9.2.3 System Call ?? ????

• ?? ?? ????
• System Call ? ???? ? ??? ??? ????.
• kernel/kernel/test_syscall.c ? ??? ?? ???.

calls.S ? ??? ??? ??? ??
? ??? ???? ??? ??? ???? ??? ? ???? keyword
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9.2.3 System Call ?? ????

• Makefile ??
• ???? ????? ??? ??? ? ?? ?? ??? ? ? ???
  kernel/kernel/Makefile? ??? ?? ?? ??.

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9.2.3 System Call ?? ????

• Kernel image? /tftpboot? ??
• kernel ?????? ??? ????? ??? ?? ???? target?
  ???? ?? /tftpboot? ??.
• cd kernel
• make menuconfig make zImage
• cp kernel/arch/arm/boot/zImage /tftpboot

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9.2.3 System Call ?? ????

• System Call? ???? user application??
• library? ??? ?? user application? ??? ??

unistd.h ? ??? ???? System Call ????? ??? ??? ???
????. sys ???? ??? ???.
/ linux/unistd.h / define _syscall0(type,name)
type name(void) \ register long __res
__asm__(r0) \ __asm__ __volatile__ \ __sysc
all(name) \ r (__res) \ \
lr) \ __syscall_return(type,__res) \
else define __syscall(name) swi\t
__sys1(__NR_name)\n\t
Software interrupt? ????? assemblier
Unistd?? ??? symbol? ????.
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9.2.3 System Call ?? ????

• Test
• ?? system call? ???? ?? ???? ??
• ???(?? /tftpboot? zImage? ??) ? target?
  download?? target ? ???? ??? ? host? /home/share
  ???
• ????? ???? ????? ??

./hybuscall Welcome to the embedded World!!
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9.2.3 System Call ?? ????

• ????? ??? ??? ?? ??? ??.
• Kernel ?? Application ??

unistd.h ? system call ?? ??
calls.S ? System Call ???? ??
system call? ???? application ??
Application ? Target system? download
System Call ?? ?? ??
Kernel ? ???
Applicatin ??
Kernel? Target system? download
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9.2.4 System Call ?? ??

• Linux ??? system call ??
• Interrupt ?? ???? ??
• Interrupt
• ?? ??? ??? ???? ?? ? ??? ?? ??? ???? ??? ???? ???
  kerenl?? ??? ????.

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9.2.4 System Call ?? ??

• System Call

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Device Driver
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??
9.3.1 Device Driver? 9.3.1 Device Driver?
?? 9.3.3 Device Driver ?? 9.3.4 ??? Driver
?????? ??? 9.3.5 Makefile ??? 9.3.6 Driver? ???
??? ?? ? ????
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9.3.1 Device Driver?(1)

• ???? hardware ??? ??? ???? software
• user application? driver?? ??? ??, driver?
  hardware? ????? ??? ??
• major number? minor number? ???? ??? devices?
  ???? ??
• device? system memory ?? data? ??? ????
• kernel ?? ??

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9.3.1 Device Driver?(2)

• Kernel

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9.3.2 Device Driver? ??
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9.3.3 Device Driver? ??(1)

• ???? device driver? ??

Printf? ?? ??? ?? ??? ?? ??
???????? ???? ????? ??? ??? ????
??? header. ????? include???
Module_init()? module_exit() ???
insmod? ??? ???? ? ??? ????. ? ?? ???
regiseter_chrdev() ?? ??? ??? ??? ????.
rmmod? ??? ??? ??? ?? ? ??? ????.
unregister_chrdev() ?? ??? ??? ??? ????.
application?? ?? ??? driver?? ?? ??? mapping
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9.3.3 Device Driver? ??(2)

• include ltlinux/module.hgt
• include ltlinux/fs.hgt
• include ltlinux/kernel.hgt
• include ltlinux/init.hgt
• define DEV_NAME SKELETON"
• int skeleton_major 0
• int result
• ///////////// ? ? ? ? //////////////
• int skeleton_open (struct inode inode, struct
  file filp)
• int skeleton_release (struct inode inode, struct
  file filp)
• ssize_t skeleton_read (struct file filp,
  unsigned int buf, size_t count, loff_t f_pos)
• ssize_t skeleton_write (struct file filp,
  unsigned int buf, size_t count, loff_t f_pos)
• int skeleton_ioctl(struct inode inode, struct
  file filp, unsigned int cmd, unsigned int arg)
• int skeleton_init()
• void skeleton_exit()

??? ??? ???? ?? register_chrdev()? parameter??
0?? ???? major?? ????? ???? ???? ?????
register_chrdev()??? return?? ?? ????. 0?? ??? ??
?? ??
application?? open()??? driver? ???? ???? ??
application?? close()??? driver? ??? ???? ??
application?? kernel??? ??? ?? ???? ??
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9.3.3 Device Driver? ??(3)

• int device_open (struct inode inode, struct file
  filp)
• printk("test_open start!!!\n")
• return 0
• int device_release (struct inode inode, struct
  file filp)
• return 0
• ssize_t device_read (struct file filp, unsigned
  int buf, size_t count, loff_t f_pos)
• printk("read() \n")
• return 0
• ssize_t device_write (struct file filp, unsigned
  int buf, size_t count, loff_t f_pos)
• return 0

Application?? read??? ???? terminal? ?? ??
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9.3.3 Device Driver? ??(4)

• int device_ioctl(struct inode inode, struct file
  filp, unsigned int cmd, unsigned int arg)
• printk("ioctl() \n")
• return 0
• struct file_operations test_fops
• .open device_open,
• .read device_read,
• .write device_write,
• .ioctl device_ioctl,
• .release device_release,
• module_init(skeleton_init)
• module_exit(skeleton_exit)

Ioctl()??? ???? ?? ??
???????? char device driver? ?? ?? ??? ????. ?
??? ??? ??? ??? ??? ???? ??. ? application??
open??? ???? ?? driver? test_open()? mapping????
?? ???? ??.
insmod? ???? ??
rmmod? ???? ??
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9.3.3 Device Driver? ??(5)

• int skeleton_init(void)
• result register_chrdev(test_major,
  DEV_NAME, test_fops)
• if (result lt 0)
• printk(KERN_WARNING "s can't get major
  d\n", DEV_NAME, test_major)
• return result
• printk("lt1gt init module success!!.. s major
  number d\n", DEV_NAME, result)
• return 0
• void skeletin_exit(void)
• if( !unregister_chrdev(result, DEV_NAME) )
• printk("s cleanup_module success...\n",
  DEV_NAME)
• else
• printk("s cleanup_module fail...\n",
  DEV_NAME)

driver? ??? ??? ???? ??, result? major ?? ???
driver? ???? ???? ??
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9.4 ??? Driver ?????? ???

• include ltstdio.hgt
• include ltfcntl.hgt
• include ltstring.hgt
• include lterrno.hgt
• int fd
• int main(int argc, char argv)
• if( (fd open("/dev/SKELETON", O_RDWR)) lt
  3)
• fprintf(stderr, "/dev/testdd device file open
  error!! .. s\n",strerror(errno))
• return 0
• read(fd, 0, 0)
• ioctl(fd, NULL,0)
• close(fd)
• return 0

File? ?? ??? ??
Error? ?? header file
mknod? ??? /dev? ???? node(file)? open??.
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9.5 Makefile ???
??? ???? ??
CC /opt/iwmmxt-1.0.0/bin/arm-linux-gcc KDIR
/PXA270/kernel/linux-2.6.11-h270-tku_v1.1
TEST_TARGET userapp TEST_OBJS
userapp.o TEST_SRCS userapp.c obj-m
skeleton.o build (TEST_TARGET) make -C
(KDIR) SUBDIRS'pwd' modules (TEST_TARGET)
(TEST_OBJS) (CC) -o _at_ (TEST_OBJS) clean
rm -rf .o .ko rm -f(TEST_TARGET)
??? ????? ??? ?? ??
Compile?? ???? ????? ??? ?? ??
??? ????? make module ??
?????? ???
??? ????? ?? ?? ????? ??
?? ????? ?? ?? ?? ????? ???
???? ??? ??
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9.6 Driver? ??? ??? ?? ? ????(1)

• Char Device Driver ?? ??
• ??? device driver? file interface (node? ??)? ??
  ??
• Device driver? ??? ???? ?? ??? major number? ??
• ??? ??? ??
• ?? int register_chrdev(unsigned int major,
  const char
  name, stuct file_operations fops)
• Major ??? major number. 0?? ???? ?? ?? ? ????
  ??
• Name device? ??
• Fops device? ?? file ?? ???
• ?? int unregister_chrdev(unsigned int major,
  const char name)

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9.6 Driver? ??? ??? ?? ? ????(2)
user program open close read write
kernel
device driver
file operations device_open device_close
device_read device_write
system call
device
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9.6 Driver? ??? ??? ?? ? ????(3)

• Major number? minor number
• ??? ???? ???? ?? ???? ?? ??? ??
• Major number ???? ???? ????? ????? ??
• Minor number ???? ???? ??? ??? ?? ???
  ???? ?? ??
• ??? ????? ??? major number? ??? ?
• register_chrdev()? ??? ??? ? major number? ??
• ?? major number? ???? ??? ?? ??
• Major? minor ??? ??? ??? ?? ?? inode? i_rdev?
  16bit? ????. ?? 10bit? major, ?? 12bit? minor??.

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9.6 Driver? ??? ??? ?? ? ????(4)

• mknod ???? ???? ????? ??? ? ?? ?? ?? ??
• mknod device file name type major minor
• Ex mknod SKELETON c 252 0
• mdev_t ??? major, minor number? ???? ????
• MAJOR() kdev_t?? major number? ???? ???
• Ex MAJOR(inode-gti_rdev)
• MINOR() kdev_t?? minor number? ???? ???
• cat /proc/devices ???? ?? ??? ???? ???? ??

C? char device drive??, block device drive? b? ??
59
9.6 Driver? ??? ??? ?? ? ????(5)

• kernel/include/linux/fs.h

??? ???? driver? ??? ???? ??
60
9.6 Driver? ??? ??? ?? ? ????(6)
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9.6 Driver? ??? ??? ?? ? ????(7)

• Device Driver? ?? ??

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9.6 Driver? ??? ??? ?? ? ????(8)

• ??? ?? ???? ??? skeleton.c, test application?
  userapp.c, ??? makefile? Makefile? ?? ? ????.
• make ???? ???? ?? 2 files? ?????.
• make
• ??? skeleton.ko ? userapp? target?? ????. ?????
  ??? ??? minicom ?? nfs??? ????.
• ???? nfs ??? ??? ??? ?????.

insmod skeleton.ko // ?? ???? ?? ????
./userapp // ?? ???? ????? ??? ???? ? ??? ??.