Re: How to avoid data copies in a driver ?

On Thu, May 15, 2008 at 1:50 PM, Arnd Hannemann <arnd@xxxxxxxxxx> wrote:
Francis Moreau wrote:
Hello,

On Wed, May 14, 2008 at 11:23 PM, linux-os (*** Johnson)
<linux-os@xxxxxxxxxxxx> 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


ok, relayfs might be what I need, thanks.


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...


The fact is that the data usually ends into a file.

thanks
--
Francis
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