From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752030AbdBTEF1 (ORCPT ); Sun, 19 Feb 2017 23:05:27 -0500 Received: from regular1.263xmail.com ([211.150.99.131]:51974 "EHLO regular1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751833AbdBTEFZ (ORCPT ); Sun, 19 Feb 2017 23:05:25 -0500 X-263anti-spam: KSV:0;BIG:0; X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-KSVirus-check: 0 X-ADDR-CHECKED: 0 X-ABS-CHECKED: 1 X-SKE-CHECKED: 1 X-RL-SENDER: wzz@rock-chips.com X-FST-TO: linux-rockchip@lists.infradead.org X-SENDER-IP: 103.29.142.67 X-LOGIN-NAME: wzz@rock-chips.com X-UNIQUE-TAG: <17caafd7f175f65f096903279187bd4d> X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 0 Subject: Re: [PATCH] drm/bridge: analogix_dp: Don't return -EBUSY when msg->size is 0 in aux transaction To: Tomasz Figa References: <1486978066-5351-1-git-send-email-wzz@rock-chips.com> Cc: Sean Paul , Daniel Vetter , Inki Dae , David Airlie , Tomeu Vizoso , Mika Kahola , =?UTF-8?Q?St=c3=a9phane_Marchesin?= , Douglas Anderson , Thierry Reding , Heiko Stuebner , Jingoo Han , Javier Martinez Canillas , "linux-kernel@vger.kernel.org" , dri-devel , linux-samsung-soc , "open list:ARM/Rockchip SoC..." From: Zain Wang Message-ID: <5c1ced2c-f182-ae3c-0edf-eb2ea5042720@rock-chips.com> Date: Mon, 20 Feb 2017 12:04:25 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tomasz, 在 2017/2/20 10:40, Tomasz Figa 写道: > Hi Zain, > > On Mon, Feb 13, 2017 at 6:27 PM, zain wang 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 >> --- >> 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 > > >