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drm/edid: Clarify validate_displayid()

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Throw out the magic '5' from validate_displayid() and replace with
the actual thing we mean sizeof(header)+checksum. Also rewrite the
checksum loop to be less hard to parse for mere mortals.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200313162054.16009-9-ville.syrjala@linux.intel.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Ville Syrjälä 2020-03-13 18:20:53 +02:00
parent 5f706b4a3b
commit bd1f64df31
1 changed files with 8 additions and 5 deletions
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13
drivers/gpu/drm/drm_edid.c
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@ -5097,7 +5097,7 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi
static int validate_displayid(u8 *displayid, int length, int idx)
{
int i;
int i, dispid_length;
u8 csum = 0;
struct displayid_hdr *base;
@ -5106,15 +5106,18 @@ static int validate_displayid(u8 *displayid, int length, int idx)
DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
base->rev, base->bytes, base->prod_id, base->ext_count);
if (base->bytes + 5 > length - idx)
/* +1 for DispID checksum */
dispid_length = sizeof(*base) + base->bytes + 1;
if (dispid_length > length - idx)
return -EINVAL;
for (i = idx; i <= base->bytes + 5; i++) {
csum += displayid[i];
}
for (i = 0; i < dispid_length; i++)
csum += displayid[idx + i];
if (csum) {
DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
return -EINVAL;
}
return 0;
}