Where do i get the api for the linux kernel that would let me access information within the kernel

I am new to Linux, After implementing a simple system call on the Linux kernel that prints to the syslog via printk,

I would like to be able to extend this application , so I can get details on the battery percentage of my laptop or check the speed of the hard drive in the computer, could any of you give me a hand on where i would get the code t开发者_JAVA百科hat would help me access this type of information within my kernel,

(I have no idea how I found printk, and I have no idea where i could get further information on printk)

also if guys could provide a simple but useful system call that I could implement myself that would be great.

This should be a good starting point for you to learn about making system calls to the kernel. This cheatsheet also has a sample C code.

Download it here (pdf)

Check out /proc and /sys on your filesystem; between the two, you should be able to find everything you need without system calls.

For example:

• What is my CPU speed? Check /proc/cpuinfo
• How much RAM do I have? Check /proc/meminfo
• What size is /dev/sda? Check /sys/block/sda/size

Some things I'm not sure how to test (for example, the two things you asked about), but you may be able to find them with a little digging.

If you're really curious how stuff works, check out the source for the drivers for the devices you are interested in; they provide those filesystem entries, so they should (hopefully) document what is in each.