drm/dp/i2c: Update comments about common i2c over dp assumptions (v3)

If you are using the common dp over i2c functionality, it is
asumed that the aux transfer function does not modify the any
of the msg structure other than the reply field.  Doing so
breaks the logic in the common code.

v2: update struct drm_dp_aux comments about assumptions
v3 (chk): rebased on upstream changes

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Thierry Reding <treding@nvidia.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Christian König <christian.koenig@amd.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index bcfb0d07718e..4b6e6f3ba0a1 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -577,7 +577,9 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter)
 
 /*
  * Transfer a single I2C-over-AUX message and handle various error conditions,
- * retrying the transaction as appropriate.
+ * retrying the transaction as appropriate.  It is assumed that the
+ * aux->transfer function does not modify anything in the msg other than the
+ * reply field.
  */
 static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 {