Re: How to avoid data copies in a driver ?

[linux-os (Dick Johnson)]

On Wed, 14 May 2008, Francis Moreau wrote:

> Hello,
>
> I'd like to optimize my driver, which receives data through a fifo and gives
> them to a user space application. In turns this application moves this data
> into a file.
>
> To avoid several useless copies, I'd like the application to pass to
> the driver
> a file descriptor (?) to  the driver and then the driver can directly
> move the
> received data to that file.
>
> Could anybody give me some example of such scheme ?
>
> Thanks,
> -- 
> Francis
> --

You memory-map the data. Impliment mmap() in your driver.
You can also impliment poll()  { select() } so your
application knows when new data are available.

You cannot use a user-mode file-descriptor in the kernel.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.22.1 on an i686 machine (5588.29 BogoMips).
My book : http://www.AbominableFirebug.com/
_


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