drm/i915: Clarify error returns from display port aux channel I/O

Use distinct error return values for each kind of aux channel I/O failure.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 3f8d7b4..818fe34 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -209,15 +209,19 @@ intel_dp_aux_ch(struct intel_output *intel_output,
 
        if ((status & DP_AUX_CH_CTL_DONE) == 0) {
                printk(KERN_ERR "dp_aux_ch not done status 0x%08x\n", status);
-               return -1;
+               return -EBUSY;
        }
 
        /* Check for timeout or receive error.
         * Timeouts occur when the sink is not connected
         */
-       if (status & (DP_AUX_CH_CTL_TIME_OUT_ERROR | DP_AUX_CH_CTL_RECEIVE_ERROR)) {
-               printk(KERN_ERR "dp_aux_ch error status 0x%08x\n", status);
-               return -1;
+       if (status & DP_AUX_CH_CTL_RECEIVE_ERROR) {
+               printk(KERN_ERR "dp_aux_ch receive error status 0x%08x\n", status);
+               return -EIO;
+       }
+       if (status & DP_AUX_CH_CTL_TIME_OUT_ERROR) {
+               printk(KERN_ERR "dp_aux_ch timeout status 0x%08x\n", status);
+               return -ETIMEDOUT;
        }
 
        /* Unload any bytes sent back from the other side */
@@ -263,7 +267,7 @@ intel_dp_aux_native_write(struct intel_output *intel_output,
                else if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_DEFER)
                        udelay(100);
                else
-                       return -1;
+                       return -EIO;
        }
        return send_bytes;
 }
@@ -299,7 +303,9 @@ intel_dp_aux_native_read(struct intel_output *intel_output,
        for (;;) {
                ret = intel_dp_aux_ch(intel_output, msg, msg_bytes,
                                      reply, reply_bytes);
-               if (ret <= 0)
+               if (ret == 0)
+                       return -EPROTO;
+               if (ret < 0)
                        return ret;
                ack = reply[0];
                if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_ACK) {
@@ -309,7 +315,7 @@ intel_dp_aux_native_read(struct intel_output *intel_output,
                else if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_DEFER)
                        udelay(100);
                else
-                       return -1;
+                       return -EIO;
        }
 }