From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Restore the correct behaviour (as in check msg.reply) when aux
->transfer() returns 0. It got removed in
commit 82922da39190 ("drm/dp_helper: Retry aux transactions on all errors")
Now I can actually dump the "entire" DPCD on a Dell UP2314Q with
ddrescue. It has some offsets in the DPCD that can't be read
for some resaon, all you get is defers. Previously ddrescue would
just give up at the first unredable offset on account of
read() returning 0 means EOF. Here's the ddrescue log
for the interested:
0x00000000 0x00001400 +
0x00001400 0x00000030 -
0x00001430 0x000001D0 +
0x00001600 0x00000030 -
0x00001630 0x0001F9D0 +
0x00021000 0x00000001 -
0x00021001 0x000DEFFF +
Cc: Lyude <cpaul@xxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 82922da39190 ("drm/dp_helper: Retry aux transactions on all errors")
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 091053e995e5..8f11b8741e42 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -203,7 +203,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
ret = aux->transfer(aux, &msg);
- if (ret > 0) {
+ if (ret >= 0) {
native_reply = msg.reply & DP_AUX_NATIVE_REPLY_MASK;
if (native_reply == DP_AUX_NATIVE_REPLY_ACK) {
if (ret == size)
--
2.7.4
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