init_completion, down(mutex) related question

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Title: init_completion, down(mutex) related question

Hello All,

I am new to the Linux Kernel programming, and still learning the OS concepts. (but project deadlines dont consider it u know ;-)

Can anyone explain why do we write driver code like this :
static void s3c24a0_ac97_write(struct ac97_codec *codec, u8 reg, u16 val)

{

        down(&CAR_mutex);

        init_completion(&CAR_completion);

        AC_CODEC_CMD = AC_CMD_ADDR(reg) | AC_CMD_DATA(val);

        wait_for_completion(&CAR_completion);

        up(&CAR_mutex);

}

why it cant be written as

static void s3c24a0_ac97_write(struct ac97_codec *codec, u8 reg, u16 val)

{

        AC_CODEC_CMD = AC_CMD_ADDR(reg) | AC_CMD_DATA(val);

}

what is the meaning of down,up,completion etc.

Thanks and Regards,

Shiv Kumar Garg

Senior Software Engineer

System LSI Division

Samsung India Software Operation

3/1 Millers Road, Bangalore

Phone: +91-80-51197777 ext 2018

email: shivg@samsung.com

_________________________________

Well done is better than Well said


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