linux-kernel - [PATCH] media: davinci-isif: avoid uninitialized variable use

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Date:   Fri, 22 Mar 2019 15:34:22 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Wenwen Wang <wang6495@....edu>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] media: davinci-isif: avoid uninitialized variable use

clang warns about a possible variable use that gcc never
complained about:

drivers/media/platform/davinci/isif.c:982:32: error: variable 'frame_size' is uninitialized when used here
      [-Werror,-Wuninitialized]
                dm365_vpss_set_pg_frame_size(frame_size);
                                             ^~~~~~~~~~
drivers/media/platform/davinci/isif.c:887:2: note: variable 'frame_size' is declared here
        struct vpss_pg_frame_size frame_size;
        ^
1 error generated.

There is no initialization for this variable at all, and there
has never been one in the mainline kernel, so we really should
not put that stack data into an mmio register.

On the other hand, I suspect that gcc checks the condition
more closely and notices that the global
isif_cfg.bayer.config_params.test_pat_gen flag is initialized
to zero and never written to from any code path, so anything
depending on it can be eliminated.

To shut up the clang warning, just remove the dead code manually,
it has probably never been used because any attempt to do so
would have resulted in undefined behavior.

Fixes: 63e3ab142fa3 ("V4L/DVB: V4L - vpfe capture - source for ISIF driver on DM365")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/media/platform/davinci/isif.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/media/platform/davinci/isif.c b/drivers/media/platform/davinci/isif.c
index 47cecd10eb9f..2dee9af6d413 100644
--- a/drivers/media/platform/davinci/isif.c
+++ b/drivers/media/platform/davinci/isif.c
@@ -884,9 +884,7 @@ static int isif_set_hw_if_params(struct vpfe_hw_if_param *params)
 static int isif_config_ycbcr(void)
 {
 	struct isif_ycbcr_config *params = &isif_cfg.ycbcr;
-	struct vpss_pg_frame_size frame_size;
 	u32 modeset = 0, ccdcfg = 0;
-	struct vpss_sync_pol sync;
 
 	dev_dbg(isif_cfg.dev, "\nStarting isif_config_ycbcr...");
 
@@ -974,13 +972,6 @@ static int isif_config_ycbcr(void)
 		/* two fields are interleaved in memory */
 		regw(0x00000249, SDOFST);
 
-	/* Setup test pattern if enabled */
-	if (isif_cfg.bayer.config_params.test_pat_gen) {
-		sync.ccdpg_hdpol = params->hd_pol;
-		sync.ccdpg_vdpol = params->vd_pol;
-		dm365_vpss_set_sync_pol(sync);
-		dm365_vpss_set_pg_frame_size(frame_size);
-	}
 	return 0;
 }
 
-- 
2.20.0