Re: [PATCH] drm/exynos/fbdev: set smem_len for fbdev

On Sun, Aug 24, 2014 at 4:50 PM, Daniel Kurtz [off-list ref] wrote:

Commit [0] stopped setting fix.smem_start and fix.smem_len when creating
the fbdev.

[0] 2f1eab8d8ab59e799f7d51d62410b398607a7bc3
  drm/exynos/fbdev: don't set fix.smem/mmio_{start,len}

However, smem_len is used by some userland applications to calculate the
size for mmap.  In particular, it is used by xf86-video-fbdev:

http://cgit.freedesktop.org/xorg/xserver/tree/hw/xfree86/fbdevhw/fbdevhw.c?id=xorg-server-1.15.99.903#n571

So, let's restore setting the smem_len to unbreak things for these users.

Note: we are still leaving smem_start set to 0.

Doesn't this cause a system crash when userspace (e.g. fbtest) writes into
the mmap()ed /dev/fb*, as the wrong MMIO region is mapped?

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