[PATCH v6 19/24] drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory

[Geert Uytterhoeven]

Hi Günter,

On Thu, Aug 8, 2019 at 5:42 AM Guenter Roeck <linux at roeck-us.net> wrote:
> On Fri, Jul 26, 2019 at 07:23:13PM +0200, Andrzej Pietrasiewicz wrote:
> > Use the ddc pointer provided by the generic connector.
> >
> > Signed-off-by: Andrzej Pietrasiewicz <andrzej.p at collabora.com>
> > Reviewed-by: Neil Armstrong <narmstrong at baylibre.com>
>
> This patch results in a crash when running qemu:versatilepb.
>
> Unable to handle kernel NULL pointer dereference at virtual address 000000c5
> pgd = (ptrval)
> [000000c5] *pgd=00000000
> Internal error: Oops: 5 [#1] ARM
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper Not tainted 5.3.0-rc1+ #1
> Hardware name: ARM-Versatile (Device Tree Support)
> PC is at sysfs_do_create_link_sd+0x38/0xd8
> LR is at sysfs_do_create_link_sd+0x38/0xd8

> [<c01ac94c>] (sysfs_do_create_link_sd) from [<c04c7fc0>] (drm_connector_register.part.1+0x40/0xa0)
> [<c04c7fc0>] (drm_connector_register.part.1) from [<c04c87e0>] (drm_connector_register_all+0x90/0xb8)
> [<c04c87e0>] (drm_connector_register_all) from [<c04cefcc>] (drm_modeset_register_all+0x44/0x6c)
> [<c04cefcc>] (drm_modeset_register_all) from [<c04b4ebc>] (drm_dev_register+0x15c/0x1c0)
> [<c04b4ebc>] (drm_dev_register) from [<c04df2f8>] (pl111_amba_probe+0x2e0/0x4ac)
> [<c04df2f8>] (pl111_amba_probe) from [<c045e8d8>] (amba_probe+0x9c/0x118)

Seeing the same thing on Salvator-XS, due to vga->ddc being -ENODEV.

> # first bad commit: [a4f9087e85de141e4e6d21ac2c583ae096cc9aba] drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory

Fix sent
https://lore.kernel.org/lkml/20190813093046.4976-1-geert+renesas@glider.be/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at 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