linux-kernel - [PATCH] drm/bridge: ti-sn65dsi86: fix a ternary type promotion bug

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Date:   Tue, 18 May 2021 12:19:30 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Andrzej Hajda <a.hajda@...sung.com>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] drm/bridge: ti-sn65dsi86: fix a ternary type promotion bug

The ti_sn_aux_transfer() function returns ssize_t (signed long).  It's
supposed to return negative error codes or the number of bytes
transferred.  The "ret" variable is int and the "len" variable is
unsigned int.

The problem is that with a ternary like this, the negative int is first
type promoted to unsigned int to match "len" at this point it is a high
positive value.  Then when it is type promoted to ssize_t (s64) it
remains a high positive value instead of sign extending and becoming a
negative again.

Fix this by removing the ternary.

Fixes: b137406d9679 ("drm/bridge: ti-sn65dsi86: If refclk, DP AUX can happen w/out pre-enable")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index bb0a0e1c6341..45a2969afb2b 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -1042,7 +1042,9 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux,
 	pm_runtime_mark_last_busy(pdata->dev);
 	pm_runtime_put_autosuspend(pdata->dev);
 
-	return ret ? ret : len;
+	if (ret)
+		return ret;
+	return len;
 }
 
 static int ti_sn_bridge_parse_dsi_host(struct ti_sn65dsi86 *pdata)
-- 
2.30.2