close timer of kernel

 

if (timer_pending(&handshking_timer))
{
    del_timer_sync(&handshking_timer);
    //init_timer(&handshking_timer);
}

create and cloase of kernel thread

Referece

http://stackoverflow.com/questions/5280693/kernel-thread-implementation

tips for control uart

http://www.termsys.demon.co.uk/vtansi.htm

Linux I2C Driver

 

linux-source/Documentation/i2c/ has lot of the information you'd need. .../writing-clients.txt is a good place to start.

Have a look at the online version:

https://www.kernel.org/doc/Documentation/i2c/writing-clients

There is an okay sort of a tutorial at:

http://renjucnair.blogspot.ca/2012/01/writing-i2c-client-driver.html

Here is a good commentary on someone writing an i2c driver and has a tutorial feel to it:

http://www.embedded-bits.co.uk/2009/i2c-in-the-2632-linux-kernel/

Here is some sample code:

http://code.google.com/p/ldd-templates/source/browse/drivers/i2c/sample-i2c-client.c

Reference

http://stackoverflow.com/questions/16728587/i2c-driver-in-linux

Getopt

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int
main (int argc, char **argv)
{
  int aflag = 0;
  int bflag = 0;
  char *cvalue = NULL;
  int index;
  int c;

  opterr = 0;

  while ((c = getopt (argc, argv, "abc:")) != -1)
    switch (c)
      {
      case 'a':
        aflag = 1;
        break;
      case 'b':
        bflag = 1;
        break;
      case 'c':
        cvalue = optarg;
        break;
      case '?':
        if (optopt == 'c')
          fprintf (stderr, "Option -%c requires an argument.\n", optopt);
        else if (isprint (optopt))
          fprintf (stderr, "Unknown option `-%c'.\n", optopt);
        else
          fprintf (stderr,
                   "Unknown option character `\\x%x'.\n",
                   optopt);
        return 1;
      default:
        abort ();
      }

  printf ("aflag = %d, bflag = %d, cvalue = %s\n",
          aflag, bflag, cvalue);

  for (index = optind; index < argc; index++)
    printf ("Non-option argument %s\n", argv[index]);
  return 0;
}

Here are some examples showing what this program prints with different combinations of arguments:

% testopt
aflag = 0, bflag = 0, cvalue = (null)

% testopt -a -b
aflag = 1, bflag = 1, cvalue = (null)

% testopt -ab
aflag = 1, bflag = 1, cvalue = (null)

% testopt -c foo
aflag = 0, bflag = 0, cvalue = foo

% testopt -cfoo
aflag = 0, bflag = 0, cvalue = foo

% testopt arg1
aflag = 0, bflag = 0, cvalue = (null)
Non-option argument arg1

% testopt -a arg1
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument arg1

% testopt -c foo arg1
aflag = 0, bflag = 0, cvalue = foo
Non-option argument arg1

% testopt -a -- -b
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument -b

% testopt -a -
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument -

An option character in this string can be followed by a colon (‘:’) to indicate that it takes a required argument. If an option character is followed by two colons (‘::’), its argument is optional.

This optarg is set by getopt to point at the value of the option argument, for those options that accept arguments.

 

Reference

[1] http://www.gnu.org/software/libc/manual/html_node/Using-Getopt.html

[2] http://www.gnu.org/software/libc/manual/html_node/Example-of-Getopt.html

[3] http://en.wikipedia.org/wiki/Getopt

MAKEFILE built-in function

How to implement built-in function as below

Text-processing function

https://www.gnu.org/software/make/manual/html_node/Text-Functions.html#Text-Functions

$(patsubst %.c,%.o,x.c.c bar.c)

Result: ‘x.c.o bar.o’

$(sort foo bar lose)

Result:‘bar foo lose’

$(word 2, foo bar baz)

Result:‘bar’

Filename manipulate function

https://www.gnu.org/software/make/manual/html_node/File-Name-Functions.html

$(dir src/foo.c hacks)

Result:‘src/ ./’

$(notdir src/foo.c hacks)

Result:‘foo.c hacks’

$(suffix src/foo.c src-1.0/bar.c hacks)

Result:‘.c .c’

$(addprefix src/,foo bar)

Result:‘src/foo src/bar’

linux command – grep

 

 

dmesg | grep -i usb

[option]

“-i” ignore the case.

cat /var/log/dmesg | less

 

 

Reference

http://manpages.ubuntu.com/manpages/utopic/man1/dmesg.1.html