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([2a01:e0a:982:cbb0:4518:5e57:ff13:b4bb]) by smtp.gmail.com with ESMTPSA id g16-20020a05600c4ed000b0040b47c53610sm17866225wmq.14.2023.12.05.00.30.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Dec 2023 00:30:14 -0800 (PST) Message-ID: <9845c9ea-9121-436f-8185-95119a461127@linaro.org> Date: Tue, 5 Dec 2023 09:30:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Neil Armstrong Reply-To: neil.armstrong@linaro.org Subject: Re: [PATCH] drm/bridge: nxp-ptn3460: fix i2c_master_send() error checking Content-Language: en-US, fr To: Dan Carpenter Cc: Sean Paul , Andrzej Hajda , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Inki Dae , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org References: <0cdc2dce-ca89-451a-9774-1482ab2f4762@moroto.mountain> <75c11af4-3f5e-4909-a3d3-8feea947d4ea@linaro.org> Autocrypt: addr=neil.armstrong@linaro.org; keydata= xsBNBE1ZBs8BCAD78xVLsXPwV/2qQx2FaO/7mhWL0Qodw8UcQJnkrWmgTFRobtTWxuRx8WWP GTjuhvbleoQ5Cxjr+v+1ARGCH46MxFP5DwauzPekwJUD5QKZlaw/bURTLmS2id5wWi3lqVH4 BVF2WzvGyyeV1o4RTCYDnZ9VLLylJ9bneEaIs/7cjCEbipGGFlfIML3sfqnIvMAxIMZrvcl9 qPV2k+KQ7q+aXavU5W+yLNn7QtXUB530Zlk/d2ETgzQ5FLYYnUDAaRl+8JUTjc0CNOTpCeik 80TZcE6f8M76Xa6yU8VcNko94Ck7iB4vj70q76P/J7kt98hklrr85/3NU3oti3nrIHmHABEB AAHNKk5laWwgQXJtc3Ryb25nIDxuZWlsLmFybXN0cm9uZ0BsaW5hcm8ub3JnPsLAkQQTAQoA OwIbIwULCQgHAwUVCgkICwUWAgMBAAIeAQIXgBYhBInsPQWERiF0UPIoSBaat7Gkz/iuBQJk Q5wSAhkBAAoJEBaat7Gkz/iuyhMIANiD94qDtUTJRfEW6GwXmtKWwl/mvqQtaTtZID2dos04 YqBbshiJbejgVJjy+HODcNUIKBB3PSLaln4ltdsV73SBcwUNdzebfKspAQunCM22Mn6FBIxQ GizsMLcP/0FX4en9NaKGfK6ZdKK6kN1GR9YffMJd2P08EO8mHowmSRe/ExAODhAs9W7XXExw UNCY4pVJyRPpEhv373vvff60bHxc1k/FF9WaPscMt7hlkbFLUs85kHtQAmr8pV5Hy9ezsSRa GzJmiVclkPc2BY592IGBXRDQ38urXeM4nfhhvqA50b/nAEXc6FzqgXqDkEIwR66/Gbp0t3+r yQzpKRyQif3OwE0ETVkGzwEIALyKDN/OGURaHBVzwjgYq+ZtifvekdrSNl8TIDH8g1xicBYp QTbPn6bbSZbdvfeQPNCcD4/EhXZuhQXMcoJsQQQnO4vwVULmPGgtGf8PVc7dxKOeta+qUh6+ SRh3vIcAUFHDT3f/Zdspz+e2E0hPV2hiSvICLk11qO6cyJE13zeNFoeY3ggrKY+IzbFomIZY 4yG6xI99NIPEVE9lNBXBKIlewIyVlkOaYvJWSV+p5gdJXOvScNN1epm5YHmf9aE2ZjnqZGoM Mtsyw18YoX9BqMFInxqYQQ3j/HpVgTSvmo5ea5qQDDUaCsaTf8UeDcwYOtgI8iL4oHcsGtUX oUk33HEAEQEAAcLAXwQYAQIACQUCTVkGzwIbDAAKCRAWmrexpM/4rrXiB/sGbkQ6itMrAIfn M7IbRuiSZS1unlySUVYu3SD6YBYnNi3G5EpbwfBNuT3H8//rVvtOFK4OD8cRYkxXRQmTvqa3 3eDIHu/zr1HMKErm+2SD6PO9umRef8V82o2oaCLvf4WeIssFjwB0b6a12opuRP7yo3E3gTCS KmbUuLv1CtxKQF+fUV1cVaTPMyT25Od+RC1K+iOR0F54oUJvJeq7fUzbn/KdlhA8XPGzwGRy 4zcsPWvwnXgfe5tk680fEKZVwOZKIEuJC3v+/yZpQzDvGYJvbyix0lHnrCzq43WefRHI5XTT QbM0WUIBIcGmq38+OgUsMYu4NzLu7uZFAcmp6h8g Organization: Linaro Developer Services In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/12/2023 17:59, Dan Carpenter wrote: > On Mon, Dec 04, 2023 at 02:53:05PM +0100, Neil Armstrong wrote: >> On 04/12/2023 13:29, Dan Carpenter wrote: >>> The i2c_master_send/recv() functions return negative error codes or the >>> number of bytes that were able to be sent/received. This code has >>> two problems. 1) Instead of checking if all the bytes were sent or >>> received, it checks that at least one byte was sent or received. >>> 2) If there was a partial send/receive then we should return a negative >>> error code but this code returns success. >>> >>> Fixes: a9fe713d7d45 ("drm/bridge: Add PTN3460 bridge driver") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Dan Carpenter >>> --- >>> This is from static analysis and code review. It's always a concern >>> when you add stricter error handling that something will break. >>> >>> drivers/gpu/drm/bridge/nxp-ptn3460.c | 10 +++++----- >>> 1 file changed, 5 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/bridge/nxp-ptn3460.c b/drivers/gpu/drm/bridge/nxp-ptn3460.c >>> index d81920227a8a..9b7eb8c669c1 100644 >>> --- a/drivers/gpu/drm/bridge/nxp-ptn3460.c >>> +++ b/drivers/gpu/drm/bridge/nxp-ptn3460.c >>> @@ -56,13 +56,13 @@ static int ptn3460_read_bytes(struct ptn3460_bridge *ptn_bridge, char addr, >>> ret = i2c_master_send(ptn_bridge->client, &addr, 1); >>> if (ret <= 0) { >>> DRM_ERROR("Failed to send i2c command, ret=%d\n", ret); >>> - return ret; >>> + return ret ?: -EIO; >>> } >>> ret = i2c_master_recv(ptn_bridge->client, buf, len); >>> - if (ret <= 0) { >>> + if (ret != len) { >> >> This is impossible, i2c_transfer_buffer_flags() returns len as-is if no error, so >> ret can only be negative or equal to len. The original code is right. > > It works, but it's not "right". The <= 0 could be changed to < 0. The > "len" variable is EDID_LENGTH (128). So indeed, switching to < 0 is the most reasonable, no need to change the ret value in this case. Neil > > regards, > dan carpenter >