linux-kernel - [PATCH] media: camss: csiphy-3ph: avoid undefined behavior

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Date:   Thu, 15 Dec 2022 17:28:46 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Robert Foss <robert.foss@...aro.org>,
        Todor Tomov <todor.too@...il.com>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnd Bergmann <arnd@...db.de>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Jonathan Marek <jonathan@...ek.ca>,
        "Bryan O'Donoghue" <bryan.odonoghue@...aro.org>,
        linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] media: camss: csiphy-3ph: avoid undefined behavior

From: Arnd Bergmann <arnd@...db.de>

Marking a case of the switch statement as unreachable means the
compiler treats it as undefined behavior, which is then caught by
an objtool warning:

drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.o: warning: objtool: csiphy_lanes_enable() falls through to next function csiphy_lanes_disable()

Instead of simply continuing execution at a random place of the
driver, print a warning and return from to the caller, which
makes it possible to understand what happens and avoids the
warning.

Fixes: 53655d2a0ff2 ("media: camss: csiphy-3ph: add support for SM8250 CSI DPHY")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c b/drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c
index 451a4c9b3d30..04baa80494c6 100644
--- a/drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c
+++ b/drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c
@@ -429,7 +429,8 @@ static void csiphy_gen2_config_lanes(struct csiphy_device *csiphy,
 		array_size = ARRAY_SIZE(lane_regs_sm8250[0]);
 		break;
 	default:
-		unreachable();
+		WARN(1, "unknown cspi version\n");
+		return;
 	}
 
 	for (l = 0; l < 5; l++) {
-- 
2.35.1