bunty wrote:
>
>
> Hello,
> I want to know when i write a kernel module which contains I/O functions like read,write,open,close on a file created by kernel module. how can those functions be called automatically when i use normal functions in user program to read/write a file?
> why standard open,read,write,close will not be called?
>
> regards,
> parag.
hi Bunty,
when you open a device file (for that matter any file) you get a file descriptor , and this file descriptor
is an index into an array of struct file * maintained in the process descriptor (struct task_struct) of your process.
And your file oprations table you pass to register_chrdev (in case of char devices) function would be sitting at that
index. So now when you call read(fd, buffer, 100) -----> it would finally call sys_read and look at the value of fd ,
and index into your fd_array maintained in task_struct and call the corresponding device_read you have defined.
hope i was clear.
Allesandro Rubini's book - Linux Device Drivers explains this with a diagram, check that out for a more clearer
explanation.
cheers,
Amith
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