linux-kernel - Re: drivers/video/fbdev/core/fbcon.c:1028:6: warning: variable 'cap' set but not used

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Message-ID: <YgFBk4PEdsH7ViII@p100>
Date:   Mon, 7 Feb 2022 16:58:11 +0100
From:   Helge Deller <deller@....de>
To:     kernel test robot <lkp@...el.com>
Cc:     Helge Deller <deller@....de>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: drivers/video/fbdev/core/fbcon.c:1028:6: warning: variable 'cap'
 set but not used

* kernel test robot <lkp@...el.com>:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   90c9e950c0def5c354b4a6154a2ddda3e5f214ac
> commit: a3f781a9d6114c1d1e01defb7aa234dec45d2a5f fbcon: Add option to enable legacy hardware acceleration
> date:   4 days ago
> config: i386-randconfig-a003 (https://download.01.org/0day-ci/archive/20220206/202202061640.zSayOYxO-lkp@intel.com/config)
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> reproduce (this is a W=1 build):
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a3f781a9d6114c1d1e01defb7aa234dec45d2a5f
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout a3f781a9d6114c1d1e01defb7aa234dec45d2a5f
>         # save the config file to linux build tree
>         mkdir build_dir
>         make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/video/fbdev/core/
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
>    drivers/video/fbdev/core/fbcon.c: In function 'fbcon_init':
> >> drivers/video/fbdev/core/fbcon.c:1028:6: warning: variable 'cap' set but not used [-Wunused-but-set-variable]
>     1028 |  int cap, ret;
>          |      ^~~

The patch below fixes the issue.
I'll send it to fbdev and dri-devel mailing lists for inclusion...

Helge


From a6a058934de962836df540c93da802171bce00b4 Mon Sep 17 00:00:00 2001
From: Helge Deller <deller@....de>
Date: Mon, 7 Feb 2022 16:49:21 +0100
Subject: [PATCH] fbcon: Avoid 'cap' set but not used warning

Fix this kernel test robot warning:

  drivers/video/fbdev/core/fbcon.c: In function 'fbcon_init':
  drivers/video/fbdev/core/fbcon.c:1028:6: warning: variable 'cap' set but not used [-Wunused-but-set-variable]

The cap variable is only used when CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
is enabled. Drop the temporary variable and use info->flags instead.

Fixes: 87ab9f6b7417 ("Revert "fbcon: Disable accelerated scrolling")
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Helge Deller <deller@....de>

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index f36829eeb5a9..2fc1b80a26ad 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -1025,7 +1025,7 @@ static void fbcon_init(struct vc_data *vc, int init)
 	struct vc_data *svc = *default_mode;
 	struct fbcon_display *t, *p = &fb_display[vc->vc_num];
 	int logo = 1, new_rows, new_cols, rows, cols;
-	int cap, ret;
+	int ret;

 	if (WARN_ON(info_idx == -1))
 	    return;
@@ -1034,7 +1034,6 @@ static void fbcon_init(struct vc_data *vc, int init)
 		con2fb_map[vc->vc_num] = info_idx;

 	info = registered_fb[con2fb_map[vc->vc_num]];
-	cap = info->flags;

 	if (logo_shown < 0 && console_loglevel <= CONSOLE_LOGLEVEL_QUIET)
 		logo_shown = FBCON_LOGO_DONTSHOW;
@@ -1137,8 +1136,8 @@ static void fbcon_init(struct vc_data *vc, int init)
 	ops->graphics = 0;

 #ifdef CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
-	if ((cap & FBINFO_HWACCEL_COPYAREA) &&
-	    !(cap & FBINFO_HWACCEL_DISABLED))
+	if ((info->flags & FBINFO_HWACCEL_COPYAREA) &&
+	    !(info->flags & FBINFO_HWACCEL_DISABLED))
 		p->scrollmode = SCROLL_MOVE;
 	else /* default to something safe */
 		p->scrollmode = SCROLL_REDRAW;