[PATCH 1/3] drm: Separate EDID Header Check from EDID Block Check

[Alex Deucher]

On Wed, Jul 6, 2011 at 7:30 PM,  <reimth at googlemail.com> wrote:
> From: Thomas Reim <rdratlos at yahoo.co.uk>
>
>    Provides function drm_edid_header_is_valid() for EDID header check
>    and replaces EDID header check part of function drm_edid_block_valid()
>    by a call of drm_edid_header_is_valid().
>    This is a prerequisite to extend DDC probing, e. g. in function
>    radeon_ddc_probe() for Radeon devices, by a central EDID header check.
>
>    Tested for kernel 2.35, 2.38 and 3.0
>
> Signed-off-by: Thomas Reim <rdratlos at yahoo.co.uk>

Reviewed-by: Alex Deucher <alexdeucher at gmail.com>

> ---
>  drivers/gpu/drm/drm_edid.c |   24 ++++++++++++++++++------
>  include/drm/drm_crtc.h     |    1 +
>  2 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 0929219..1bbb85b 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -127,6 +127,23 @@ static const u8 edid_header[] = {
>        0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00
>  };
>
> + /*
> + * Sanity check the header of the base EDID block.  Return 8 if the header
> + * is perfect, down to 0 if it's totally wrong.
> + */
> +int drm_edid_header_is_valid(const u8 *raw_edid)
> +{
> +       int i, score = 0;
> +
> +       for (i = 0; i < sizeof(edid_header); i++)
> +               if (raw_edid[i] == edid_header[i])
> +                       score++;
> +
> +       return score;
> +}
> +EXPORT_SYMBOL(drm_edid_header_is_valid);
> +
> +
>  /*
>  * Sanity check the EDID block (base or extension).  Return 0 if the block
>  * doesn't check out, or 1 if it's valid.
> @@ -139,12 +156,7 @@ drm_edid_block_valid(u8 *raw_edid)
>        struct edid *edid = (struct edid *)raw_edid;
>
>        if (raw_edid[0] == 0x00) {
> -               int score = 0;
> -
> -               for (i = 0; i < sizeof(edid_header); i++)
> -                       if (raw_edid[i] == edid_header[i])
> -                               score++;
> -
> +               int score = drm_edid_header_is_valid(raw_edid);
>                if (score == 8) ;
>                else if (score >= 6) {
>                        DRM_DEBUG("Fixing EDID header, your hardware may be failing\n");
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 33d12f8..0ec3687 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -802,6 +802,7 @@ extern struct drm_display_mode *drm_gtf_mode_complex(struct drm_device *dev,
>  extern int drm_add_modes_noedid(struct drm_connector *connector,
>                                int hdisplay, int vdisplay);
>
> +extern int drm_edid_header_is_valid(const u8 *raw_edid);
>  extern bool drm_edid_is_valid(struct edid *edid);
>  struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
>                                           int hsize, int vsize, int fresh);
> --
> 1.7.1
>
>