I opened a header file .There i saw some macros but i don't know where have come from.Could you help me to know those macros and their sourc
 

Attachment 28601
what does #define ACPI_PLD_GET_REVISION(dword) ACPI_GET_BITS (dword, 0, ACPI_7BIT_MASK) mean

Their source is the header file acbuffer.h. They seem to be related to the management and usage of ACPI. If you want to know what they are for, you might get information from the kernel documentation.

There is a macro named ACPI_GET_BITS, which takes three parameters. ACPI_PLD_GET_REVISION is another macro, which calls ACPI_GET_BITS and sets two of its parameters to constant values.

From their naming, I guess that ACPI_GET_BITS is a general lookup function that gets certain bits from its dword input. ACPI_PLD_GET_REVISION then retrieves those bits that indicate the ACPI PLD revision.

A bit closer to the beginning of the file, you see that struct acpi_pld_info does contain a revision in its first byte. Also note the comment in the same file that these macros convert a _PLD buffer to internal ACPI_PLD_INFO format.

Unfortunately, I don’t know what ACPI PLD stands for, but I am sure Google does.

Why do you want to know these details?

I am new in programming .I think it will be easier to be a good programmer (like you and many other) if i know how other programmer build the whole system. please pardon me for my bad english and for my style of writing.but for people like you i am sure one day i will be a good programmer .

Your English is more than adequate. Better than many.

It's laudable that you want to understand the Linux kernel in order to gain programming skills, but I am afraid the code you picked is too advanced for a beginner. It's very close to the hardware and needs to solve very peculiar problems. Perhaps the Linux kernel in general is not the right example for a beginner.

Unfortunately, I am not a programmer and don't have suggestions which project to study instead. After a bit of googling I stumbled on this list. Give it a try and persevere.