Re: [PATCH 2.6.20 1/1] fbdev,mm: hecuba/E-Ink fbdev driver

Geert Uytterhoeven
2007-02-20T08:08:05Z

On Mon, 19 Feb 2007, Jaya Kumar wrote:
> On 2/18/07, Paul Mundt <lethal@linux-sh.org> wrote:
> > Given that, this would have to be something that's dealt with at the
> > subsystem level rather than in individual drivers, hence the desire to
> > see something like this more generically visible.
> >
>
> Hi Peter, Paul, fbdev folk,
>
> Ok. Here's what I'm thinking for abstracting this:
>
> fbdev drivers would setup fb_mmap with their own_mmap as usual. In
> own_mmap, they would do what they normally do and setup a vm_ops. They
> are free to have their own nopage handler but would set the
> page_mkwrite handler to be fbdev_deferred_io_mkwrite().
> fbdev_deferred_io_mkwrite would build up the list of touched pages and
> pass it to a delayed workqueue which would then mkclean on each page
> and then pass a copy of that page list down to a driver's callback
> function. The fbdev driver's callback function can then do the actual
> IO to the framebuffer or coalesce DMA based on the provided page list.
>
> I would like to add something like the following to struct fb_info:
>
> #ifdef CONFIG_FB_DEFERRED_IO
> struct fb_deferred_io *defio;
> #endif

Don't you need a way to specify the maximum deferral time? E.g. a field in
fb_info.

> to store the mutex (to protect the page list), the touched page list,
> and the driver's callback function.
>
> I hope this sounds sufficiently generic to meet everyone's (the two of
> us? :) needs.

Looks fine!

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds