On Sun, Jan 07, 2024 at 01:41:34AM +0800, kernel test robot wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > head: 95c8a35f1c017327eab3b6a2ff5c04255737c856 > commit: 66603243f5283f7f28c795f09e7c2167233df0bd Input: add driver for Hynitron cstxxx touchscreens > date: 1 year, 2 months ago > config: x86_64-randconfig-x051-20230705 (https://download.01.org/0day-ci/archive/20240107/202401070147.gqwVulOn-lkp@xxxxxxxxx/config) > compiler: gcc-12 (Debian 12.2.0-14) 12.2.0 > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240107/202401070147.gqwVulOn-lkp@xxxxxxxxx/reproduce) > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > the same patch/commit), kindly add following tags > | Reported-by: kernel test robot <lkp@xxxxxxxxx> > | Closes: https://lore.kernel.org/oe-kbuild-all/202401070147.gqwVulOn-lkp@xxxxxxxxx/ > > sparse warnings: (new ones prefixed by >>) > drivers/input/touchscreen/hynitron_cstxxx.c: note: in included file (through arch/x86/include/generated/asm/unaligned.h): > >> include/asm-generic/unaligned.h:119:16: sparse: sparse: cast truncates bits from constant value (aa01a0 becomes a0) > include/asm-generic/unaligned.h:120:20: sparse: sparse: cast truncates bits from constant value (aa01 becomes 1) > >> include/asm-generic/unaligned.h:119:16: sparse: sparse: cast truncates bits from constant value (ab00d0 becomes d0) > include/asm-generic/unaligned.h:120:20: sparse: sparse: cast truncates bits from constant value (ab00 becomes 0) > > vim +119 include/asm-generic/unaligned.h > > 803f4e1eab7a89 Arnd Bergmann 2021-05-08 116 > 803f4e1eab7a89 Arnd Bergmann 2021-05-08 117 static inline void __put_unaligned_le24(const u32 val, u8 *p) > 803f4e1eab7a89 Arnd Bergmann 2021-05-08 118 { > 803f4e1eab7a89 Arnd Bergmann 2021-05-08 @119 *p++ = val; > 803f4e1eab7a89 Arnd Bergmann 2021-05-08 120 *p++ = val >> 8; > 803f4e1eab7a89 Arnd Bergmann 2021-05-08 121 *p++ = val >> 16; > 803f4e1eab7a89 Arnd Bergmann 2021-05-08 122 } > 803f4e1eab7a89 Arnd Bergmann 2021-05-08 123 This is not really a kernel/driver bug, just sparse being over-eager with truncation detection. I wonder if we could make sparse skip this check on forced casts like this: diff --git a/expand.c b/expand.c index f14e7181..5487e8b3 100644 --- a/expand.c +++ b/expand.c @@ -96,6 +96,7 @@ static long long get_longlong(struct expression *expr) void cast_value(struct expression *expr, struct symbol *newtype, struct expression *old) { + enum expression_type cast_type = expr->type; struct symbol *oldtype = old->ctype; int old_size = oldtype->bit_size; int new_size = newtype->bit_size; @@ -133,7 +134,7 @@ Int: expr->value = value & mask; // Stop here unless checking for truncation - if (!Wcast_truncate || conservative) + if (cast_type == EXPR_FORCE_CAST || !Wcast_truncate || conservative) return; // Check if we dropped any bits.. and then in the kernel we would do this: diff --git a/include/asm-generic/unaligned.h b/include/asm-generic/unaligned.h index 699650f81970..034237d12d70 100644 --- a/include/asm-generic/unaligned.h +++ b/include/asm-generic/unaligned.h @@ -104,9 +104,9 @@ static inline u32 get_unaligned_le24(const void *p) static inline void __put_unaligned_be24(const u32 val, u8 *p) { - *p++ = val >> 16; - *p++ = val >> 8; - *p++ = val; + *p++ = (__force u8)(val >> 16); + *p++ = (__force u8)(val >> 8); + *p++ = (__force u8)val; } static inline void put_unaligned_be24(const u32 val, void *p) @@ -116,9 +116,9 @@ static inline void put_unaligned_be24(const u32 val, void *p) static inline void __put_unaligned_le24(const u32 val, u8 *p) { - *p++ = val; - *p++ = val >> 8; - *p++ = val >> 16; + *p++ = (__force u8)val; + *p++ = (__force u8)(val >> 8); + *p++ = (__force u8)(val >> 16); } static inline void put_unaligned_le24(const u32 val, void *p) @@ -128,12 +128,12 @@ static inline void put_unaligned_le24(const u32 val, void *p) static inline void __put_unaligned_be48(const u64 val, u8 *p) { - *p++ = val >> 40; - *p++ = val >> 32; - *p++ = val >> 24; - *p++ = val >> 16; - *p++ = val >> 8; - *p++ = val; + *p++ = (__force u8)(val >> 40); + *p++ = (__force u8)(val >> 32); + *p++ = (__force u8)(val >> 24); + *p++ = (__force u8)(val >> 16); + *p++ = (__force u8)(val >> 8); + *p++ = (__force u8)val; } static inline void put_unaligned_be48(const u64 val, void *p) What do you think? Thanks. -- Dmitry
