Hi Tomasz, ? 2017/2/20 10:40, Tomasz Figa ??: > Hi Zain, > > On Mon, Feb 13, 2017 at 6:27 PM, zain wang <wzz at rock-chips.com> wrote: >> The analogix_dp_transfer() will return -EBUSY if num_transferred is zero. >> But sometimes we will send a bare address packet to start the transaction, >> like drm_dp_i2c_xfer() show: >> ...... >> /* Send a bare address packet to start the transaction. >> * Zero sized messages specify an address only (bare >> * address) transaction. >> */ >> msg.buffer = NULL; >> msg.size = 0; >> err = drm_dp_i2c_do_msg(aux, &msg); >> ...... >> >> In this case, the msg->size is zero, so the num_transferred will be zero too. >> We can't return -EBUSY here, let's we return num_transferred if num_transferred >> equals msg->size. >> > Please see my question inline. > >> Signed-off-by: zain wang <wzz at rock-chips.com> >> --- >> 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 303083a..5384aca 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 > 0 ? num_transferred : -EBUSY; >> + return (num_transferred == msg->size) ? num_transferred : -EBUSY; > I might be missing something but, looking at the code, I don't see any > possibility of num_transferred ever being different than msg->size. To > be honest, it doesn't seem to even make any sense keeping the local > variable there, because msg->size can be simply always returned, as > errors are handled by jumping to aux_error label. Yeah, I agree with you. The better way to fix this issue is to revert the changes https://patchwork.kernel.org/patch/9411711/ (returning num_transferred directly may be better here) Maybe we can revert the changes above with some new comment. @Sean, How do you think about Tomasz's comment? Thanks Zain > > Best regards, > Tomasz > > >
