drm/i915: Don't attempt to read an unitialized stack value

If intel_sdvo_get_value() fails here, val is unitialized and the cross
check will compare the pipe config multiplier with a bogus value.

Instead, only set encoder_pixel_multiplier when the sdvo command has
been successful. The cross check will compare the pipe config value with
0 otherwise.

v2: Do the cross check with the initial value of encoder_pixel_multiplier (0)
if the sdvo command fails (and thus keep the warning) (Daniel Vetter)

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index 8415d6a..798df11 100644 (file)
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1357,17 +1357,19 @@ static void intel_sdvo_get_config(struct intel_encoder *encoder,
        }
 
        /* Cross check the port pixel multiplier with the sdvo encoder state. */
-       intel_sdvo_get_value(intel_sdvo, SDVO_CMD_GET_CLOCK_RATE_MULT, &val, 1);
-       switch (val) {
-       case SDVO_CLOCK_RATE_MULT_1X:
-               encoder_pixel_multiplier = 1;
-               break;
-       case SDVO_CLOCK_RATE_MULT_2X:
-               encoder_pixel_multiplier = 2;
-               break;
-       case SDVO_CLOCK_RATE_MULT_4X:
-               encoder_pixel_multiplier = 4;
-               break;
+       if (intel_sdvo_get_value(intel_sdvo, SDVO_CMD_GET_CLOCK_RATE_MULT,
+                                &val, 1)) {
+               switch (val) {
+               case SDVO_CLOCK_RATE_MULT_1X:
+                       encoder_pixel_multiplier = 1;
+                       break;
+               case SDVO_CLOCK_RATE_MULT_2X:
+                       encoder_pixel_multiplier = 2;
+                       break;
+               case SDVO_CLOCK_RATE_MULT_4X:
+                       encoder_pixel_multiplier = 4;
+                       break;
+               }
        }
 
        WARN(encoder_pixel_multiplier != pipe_config->pixel_multiplier,