[uClinux-dev] Two questions about drivers

Greg Ungerer gerg at snapgear.com
Thu Nov 29 00:00:14 EST 2001


Hi Joey,

JoeyShen wrote:
> I've already made my very simple device work. But there're still two problems puzzled me.
> One is that the "device_open( )" functions written in the device drivers have different parameters from the "open" system call. What is the magic between the registered driver functions and system calls?

Follow the flow of execution from the open system call 
entry point in ~/linux/fs/open.c, function is sys_open().


> The second is what will happen if I use interruptible_sleep_on( ) in my read function of the device driver and then I open the device with the parameter "O_NONBLOCK"(in the case of select( ) use). Will the device go to sleep?

Yes. It is up to the driver code to honor the O_NONBLOCK flag.
(And you don't need this flag to use select(). The idea is that
you select until you can read, and thus the read will not block
when you do call it).

Regards
Greg


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