linux-kernel - [PATCH] drm/bridge: nxp-ptn3460: fix i2c_master

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Message-ID: <0cdc2dce-ca89-451a-9774-1482ab2f4762@moroto.mountain>
Date:   Mon, 4 Dec 2023 15:29:00 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     Sean Paul <seanpaul@...omium.org>
Cc:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Inki Dae <inki.dae@...sung.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] drm/bridge: nxp-ptn3460: fix i2c_master_send() error checking

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@...r.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
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) {
 		DRM_ERROR("Failed to recv i2c data, ret=%d\n", ret);
-		return ret;
+		return ret < 0 ? ret : -EIO;
 	}
 
 	return 0;
@@ -78,9 +78,9 @@ static int ptn3460_write_byte(struct ptn3460_bridge *ptn_bridge, char addr,
 	buf[1] = val;
 
 	ret = i2c_master_send(ptn_bridge->client, buf, ARRAY_SIZE(buf));
-	if (ret <= 0) {
+	if (ret != ARRAY_SIZE(buf)) {
 		DRM_ERROR("Failed to send i2c command, ret=%d\n", ret);
-		return ret;
+		return ret < 0 ? ret : -EIO;
 	}
 
 	return 0;
-- 
2.42.0