drm/i915: support address only i2c-over-aux transactions

To support bare address requests used by the drm dp helpers.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index a0dad1a2f819f3365cb6d96ec033f47575da59c6..d2a55884ad523b8a54546bfbbe0565889e73261e 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -575,7 +575,8 @@ out:
        return ret;
 }
 
-#define HEADER_SIZE    4
+#define BARE_ADDRESS_SIZE      3
+#define HEADER_SIZE            (BARE_ADDRESS_SIZE + 1)
 static ssize_t
 intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 {
@@ -592,7 +593,7 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
        switch (msg->request & ~DP_AUX_I2C_MOT) {
        case DP_AUX_NATIVE_WRITE:
        case DP_AUX_I2C_WRITE:
-               txsize = HEADER_SIZE + msg->size;
+               txsize = msg->size ? HEADER_SIZE + msg->size : BARE_ADDRESS_SIZE;
                rxsize = 1;
 
                if (WARN_ON(txsize > 20))
@@ -611,7 +612,7 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 
        case DP_AUX_NATIVE_READ:
        case DP_AUX_I2C_READ:
-               txsize = HEADER_SIZE;
+               txsize = msg->size ? HEADER_SIZE : BARE_ADDRESS_SIZE;
                rxsize = msg->size + 1;
 
                if (WARN_ON(rxsize > 20))