linux-kernel - [PATCH] media: tuner-simple: fix regression in simple_set_radio

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Message-Id: <20200822211547.4595-1-trix@redhat.com>
Date:   Sat, 22 Aug 2020 14:15:47 -0700
From:   trix@...hat.com
To:     mchehab@...nel.org, mkrufky@...uxtv.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] media: tuner-simple: fix regression in simple_set_radio_freq

From: Tom Rix <trix@...hat.com>

clang static analysis reports this problem

tuner-simple.c:714:13: warning: Assigned value is
  garbage or undefined
        buffer[1] = buffer[3];
                  ^ ~~~~~~~~~
In simple_set_radio_freq buffer[3] used to be done
in-function with a switch of tuner type, now done
by a call to simple_radio_bandswitch which has this case

	case TUNER_TENA_9533_DI:
	case TUNER_YMEC_TVF_5533MF:
		tuner_dbg("This tuner doesn't ...
		return 0;

which does not set buffer[3].  In the old logic, this case
would have returned 0 from simple_set_radio_freq.

Recover this old behavior by returning an error for this
codition. Since the old simple_set_radio_freq behavior
returned a 0, do the same.

Fixes: c7a9f3aa1e1b ("V4L/DVB (7129): tuner-simple: move device-specific code into three separate functions")
Signed-off-by: Tom Rix <trix@...hat.com>
---
 drivers/media/tuners/tuner-simple.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/media/tuners/tuner-simple.c b/drivers/media/tuners/tuner-simple.c
index b6e70fada3fb..8fb186b25d6a 100644
--- a/drivers/media/tuners/tuner-simple.c
+++ b/drivers/media/tuners/tuner-simple.c
@@ -500,7 +500,7 @@ static int simple_radio_bandswitch(struct dvb_frontend *fe, u8 *buffer)
 	case TUNER_TENA_9533_DI:
 	case TUNER_YMEC_TVF_5533MF:
 		tuner_dbg("This tuner doesn't have FM. Most cards have a TEA5767 for FM\n");
-		return 0;
+		return -EINVAL;
 	case TUNER_PHILIPS_FM1216ME_MK3:
 	case TUNER_PHILIPS_FM1236_MK3:
 	case TUNER_PHILIPS_FMD1216ME_MK3:
@@ -702,7 +702,8 @@ static int simple_set_radio_freq(struct dvb_frontend *fe,
 		    TUNER_RATIO_SELECT_50; /* 50 kHz step */
 
 	/* Bandswitch byte */
-	simple_radio_bandswitch(fe, &buffer[0]);
+	if (simple_radio_bandswitch(fe, &buffer[0]))
+		return 0;
 
 	/* Convert from 1/16 kHz V4L steps to 1/20 MHz (=50 kHz) PLL steps
 	   freq * (1 Mhz / 16000 V4L steps) * (20 PLL steps / 1 MHz) =
-- 
2.18.1