Re: [akpm-mm:mm-nonmm-unstable 36/41] include/linux/build_bug.h:16:51: error: negative width in bit-field '<anonymous>'

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Wed, Oct 19, 2022 at 01:27:05AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-nonmm-unstable
> head:   c05e49b87cb71437bbc18a6c16dd8113623d7778
> commit: 20b6f49e6024be96a0a729839f7a127600d08740 [36/41] minmax: sanity check constant bounds when clamping
> config: arm-defconfig
> compiler: arm-linux-gnueabi-gcc (GCC) 12.1.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?id=20b6f49e6024be96a0a729839f7a127600d08740
>         git remote add akpm-mm https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git
>         git fetch --no-tags akpm-mm mm-nonmm-unstable
>         git checkout 20b6f49e6024be96a0a729839f7a127600d08740
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash drivers/net/wireless/ralink/rt2x00/
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from include/linux/container_of.h:5,
>                     from include/linux/kernel.h:21,
>                     from drivers/net/wireless/ralink/rt2x00/rt2800lib.c:25:
>    drivers/net/wireless/ralink/rt2x00/rt2800lib.c: In function 'rt2800_txpower_to_dev':
> >> include/linux/build_bug.h:16:51: error: negative width in bit-field '<anonymous>'
>       16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
>          |                                                   ^
>    include/linux/minmax.h:50:10: note: in expansion of macro 'BUILD_BUG_ON_ZERO'
>       50 |         (BUILD_BUG_ON_ZERO(__builtin_choose_expr(                               \
>          |          ^~~~~~~~~~~~~~~~~
>    include/linux/minmax.h:54:9: note: in expansion of macro '__clamp_input_check'
>       54 |         __clamp_input_check(lo, hi) +                                           \
>          |         ^~~~~~~~~~~~~~~~~~~
>    include/linux/minmax.h:146:36: note: in expansion of macro '__careful_clamp'
>      146 | #define clamp_t(type, val, lo, hi) __careful_clamp((type)(val), (type)(lo), (type)(hi))
>          |                                    ^~~~~~~~~~~~~~~
>    drivers/net/wireless/ralink/rt2x00/rt2800lib.c:4054:24: note: in expansion of macro 'clamp_t'
>     4054 |                 return clamp_t(char, txpower, MIN_A_TXPOWER, MAX_A_TXPOWER);
>          |                        ^~~~~~~

Because char is heck broken in C standard, it may be signed or unsigned
depending on the compiler (IIRC), so perhaps fixing it to signed char will fix
it?

From 6b711ba6b1086795d2407db447ed817aaa791063 Mon Sep 17 00:00:00 2001
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: Tue, 18 Oct 2022 23:35:06 +0300
Subject: [PATCH 1/1] rt2x00: Avoid using 'char' for signed operations

The default Tx power is defined as 'short' in the data structure.
There is nothing prevents us to use 'short' in the
rt2800_txpower_to_dev(). With 'char' it's implementation defined
signedess and sometimes it may be tricky.

  drivers/net/wireless/ralink/rt2x00/rt2800lib.c: In function 'rt2800_txpower_to_dev':
  include/linux/build_bug.h:16:51: error: negative width in bit-field '<anonymous>'
  ...
  drivers/net/wireless/ralink/rt2x00/rt2800lib.c:4054:24: note: in expansion of macro 'clamp_t'
  4054 |  return clamp_t(char, txpower, MIN_A_TXPOWER, MAX_A_TXPOWER);

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/net/wireless/ralink/rt2x00/rt2800lib.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
index cbbb1a4849cf..d7dffea6df82 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
@@ -4035,23 +4035,22 @@ static void rt2800_iq_calibrate(struct rt2x00_dev *rt2x00dev, int channel)
 	rt2800_bbp_write(rt2x00dev, 159, cal != 0xff ? cal : 0);
 }
 
-static char rt2800_txpower_to_dev(struct rt2x00_dev *rt2x00dev,
-				  unsigned int channel,
-				  char txpower)
+static short rt2800_txpower_to_dev(struct rt2x00_dev *rt2x00dev,
+				   unsigned int channel, short txpower)
 {
 	if (rt2x00_rt(rt2x00dev, RT3593) ||
 	    rt2x00_rt(rt2x00dev, RT3883))
 		txpower = rt2x00_get_field8(txpower, EEPROM_TXPOWER_ALC);
 
 	if (channel <= 14)
-		return clamp_t(char, txpower, MIN_G_TXPOWER, MAX_G_TXPOWER);
+		return clamp_t(short, txpower, MIN_G_TXPOWER, MAX_G_TXPOWER);
 
 	if (rt2x00_rt(rt2x00dev, RT3593) ||
 	    rt2x00_rt(rt2x00dev, RT3883))
-		return clamp_t(char, txpower, MIN_A_TXPOWER_3593,
+		return clamp_t(short, txpower, MIN_A_TXPOWER_3593,
 			       MAX_A_TXPOWER_3593);
 	else
-		return clamp_t(char, txpower, MIN_A_TXPOWER, MAX_A_TXPOWER);
+		return clamp_t(short, txpower, MIN_A_TXPOWER, MAX_A_TXPOWER);
 }
 
 static void rt3883_bbp_adjust(struct rt2x00_dev *rt2x00dev,
-- 
2.35.1


-- 
With Best Regards,
Andy Shevchenko