Reference from drm_dp_aux description (about transfer):
Upon success, the implementation should return the number of payload bytes
that were transferred, or a negative error-code on failure. Helpers
propagate errors from the .transfer() function, with the exception of
the -EBUSY error, which causes a transaction to be retried. On a short,
helpers will return -EPROTO to make it simpler to check for failure.
The analogix_dp_transfer will return num_transferred, but if there is none
byte been transferred, the return value will be 0, which means success, we
should return error-code if transfer none byte.
for (retry = 0; retry < 32; retry++) {
err = aux->transfer(aux, &msg);
if (err < 0) {
if (err == -EBUSY)
continue;
goto unlock;
}
}
Cc: zain wang <wzz@xxxxxxxxxxxxxx>
Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
Signed-off-by: Jianqun Xu <jay.xu@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
index cd37ac0..303083a 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
@@ -1162,5 +1162,5 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
(msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_NATIVE_READ)
msg->reply = DP_AUX_NATIVE_REPLY_ACK;
- return num_transferred;
+ return num_transferred > 0 ? num_transferred : -EBUSY;
}
--
1.9.1
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