Re: [Linux-fbdev-devel] Re: [PATCH] fbdev: colormap fixes

Geert Uytterhoeven
2005-07-28T16:00:22Z

On Thu, 28 Jul 2005, Antonino A. Daplas wrote:
> Jon Smirl wrote:
> > On 7/28/05, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > On Wed, 27 Jul 2005, Linux Kernel Mailing List wrote:
> >
> > There are a couple of ways to fix this.
> > 1) Add a check to limit use of the sysfs attributes to 256 entries. If
> > you want more you have to use /dev/fb0 and the ioctl. More is an
> > uncommon case.
> > 2) Switch this to a binary parameter. Now you have to use tools like
> > hexdump instead of cat to work with the data. It was nice to be able
> > to use cat to see the current map.
> >
> > Does anyone have preferences for which way to fix it?
>
> Or...
>
> 3) Add another file in sysfs which specifies at what index and how many
> entries will be read or written from or to the cmap. With this additional
> sysfs file, it should be able to handle any reasonable cmap length, but
> it will take more than one reading of the color_map file. Another
> advantage is that the entire color map need not be read or written if
> only one field needs to be changed.
>
> I've attached a test patch. Let me know what you think.

I like it! ... But, a disadvantages is that it needs to store state between two
non-atomic operations. E.g. imagine two processes doing this at the same time.

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