Re: How to avoid data copies in a driver ?

Arnd Hannemann
2008-05-15T11:50:44Z

Francis Moreau wrote:
> Hello,
>
> On Wed, May 14, 2008 at 11:23 PM, linux-os (Dick Johnson)
> <linux-os@analogic.com> wrote:
>> 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.
>>
>
> Why not ?

http://kernelnewbies.org/FAQ/WhyWritingFilesFromKernelIsBad

>
> I'm suprised because what I need doens't seem so uncommon, usually
> devices send or
> receive data to/from files. So a helper (system call ?) to achieve
> that other than the basic
> read/write seems needed, no ?

Usually devices send or receive just data, and they shouldn't care about
file format, filesystems, permissions and all this stuff...

Regards,
Arnd