@@ -2017,13 +2017,21 @@ struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
}
}
+static bool
+is_display_descriptor(const u8 *r, u8 tag)
+{
+ return (!r[0] && !r[1] && !r[2] && r[3] == tag) ? true : false;
+}
+
static void
is_rb(struct detailed_timing *t, void *data)
{
u8 *r = (u8 *)t;
- if (r[3] == EDID_DETAIL_MONITOR_RANGE)
- if (r[15] & 0x10)
- *(bool *)data = true;
+
+ if (is_display_descriptor(r, EDID_DETAIL_MONITOR_RANGE)) {
+ if (r[10] == BIT(2))
+ *(int *)data = !!(r[15] & 0x10);
+ }
}
/* EDID 1.4 defines this explicitly. For EDID 1.3, we guess, badly. */
@@ -2031,9 +2039,13 @@ struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
drm_monitor_supports_rb(struct edid *edid)
{
if (edid->revision >= 4) {
- bool ret = false;
- drm_for_each_detailed_block((u8 *)edid, is_rb, &ret);
- return ret;
+ if (edid->features & BIT(0)) {
+ int ret = -1;
+
+ drm_for_each_detailed_block((u8 *)edid, is_rb, &ret);
+ if (ret != -1)
+ return ret;
+ }
}
return ((edid->input & DRM_EDID_INPUT_DIGITAL) != 0);
According to VESA ENHANCED EXTENDED DISPLAY IDENTIFICATION DATA STANDARD (Defines EDID Structure Version 1, Revision 4) page: 39 How to determine whether the monitor support RB timing or not? EDID 1.4 First: read detailed timing descriptor and make sure byte 0 = 0x00, byte 1 = 0x00, byte 2 = 0x00 and byte 3 = 0xFD Second: read EDID bit 0 in feature support byte at address 18h = 1 and detailed timing descriptor byte 10 = 0x04 Third: if EDID bit 0 in feature support byte = 1 && detailed timing descriptor byte 10 = 0x04 then we can check byte 15, if bit 4 in byte 15 = 1 is support RB if EDID bit 0 in feature support byte != 1 || detailed timing descriptor byte 10 != 0x04, then byte 15 can not be used The linux code is_rb function not follow the VESA's rule Signed-off-by: Allen Chen <allen.chen@ite.com.tw> Reported-by: kbuild test robot <lkp@intel.com> --- drivers/gpu/drm/drm_edid.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-)