Re: extra large DMA buffer for PCI-E device under UIO

Hans J. Koch
2011-11-21T18:17:35Z

On Mon, Nov 21, 2011 at 09:36:20AM -0800, Greg KH wrote:
> On Mon, Nov 21, 2011 at 10:31:07AM -0500, Jean-Francois Dagenais wrote:
> > Hi Greg, thanks for your answer...
> >
> > On Nov 18, 2011, at 17:08, Greg KH wrote:
> >
> > > On Fri, Nov 18, 2011 at 04:16:23PM -0500, Jean-Francois Dagenais wrote:
> > >> Hello fellow hackers.
> > >>
> > >> I am maintaining a UIO based driver for a PCI-E data acquisition device.
> > >>
> > >> I map BAR0 of the device to userspace. I also map two memory areas,
> > >> one is used to feed instructions to the acquisition device, the other
> > >> is used autonomously by the PCI device to write the acquired data.
> > >
> > > Nice, have a pointer to your driver anywhere so we can include it in the
> > > main kernel tree to make your life easier?
> > As I said in a parallel answer from "Hans J. Koch" <hjk@hansjkoch.de>,
> > the driver, although GPL'ed, is quite uninteresting except for us here at
> > Sonatest.
>
> I really doubt that,

So do I. We never had a driver allocating so much memory.

> and you should submit it anyway to allow us to
> change it when the in-kernel apis change in the future. It will save
> you time in the long run and make things easier for you (look, your
> driver is automatically included in all distros!, people fix your bugs,
> etc.)

Exactly.

>
> > About merging the driver to mainline, I guess it would only be interesting for
> > the recipe I demonstrate. Please advise.
>
> That is a recipe that I'm sure others will use, and need help on in the
> future.

They already needed it in the past, and they usually try to get it by
writing me private mail.

>
> So please submit a patch, that will make it easier to help you out.

Yes, please do. The more different drivers we have under /drivers/uio, the
better. Didn't you use one of the existing drivers as a template for yours?

Thanks,
Hans