Messages in this thread Patch in this message | | | Date | Fri, 27 Jun 2014 16:09:39 -0500 | From | Brian W Hart <> | Subject | [PATCH] cpufreq: make table sentinal macros unsigned to match use |
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Commit 5eeaf1f18973 (cpufreq: Fix build error on some platforms that use cpufreq_for_each_*) moved function cpufreq_next_valid() to a public header. Warnings are now generated when objects including that header are built with -Wsign-compare (as an out-of-tree module might be):
.../include/linux/cpufreq.h: In function ‘cpufreq_next_valid’: .../include/linux/cpufreq.h:519:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while ((*pos)->frequency != CPUFREQ_TABLE_END) ^ .../include/linux/cpufreq.h:520:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if ((*pos)->frequency != CPUFREQ_ENTRY_INVALID) ^
Constants CPUFREQ_ENTRY_INVALID and CPUFREQ_TABLE_END are signed, but are used with unsigned member 'frequency' of cpufreq_frequency_table. Update the macro definitions to be explicitly unsigned to match their use.
This also corrects potentially wrong behavior of clk_rate_table_iter() if unsigned long is wider than usigned int.
Signed-off-by: Brian W Hart <hartb@linux.vnet.ibm.com> --- These macros are fairly broadly used in the kernel so I was bit leery of changing them, but after inspection I think it's fine. I found 102 uses of the macros, of which:
99 are uses with cpufreq_frequency_table.frequency (95) or with local variables of the same type as frequency (4). These should be just fine with this change--we're just making explicit a conversion that was previously implicit.
2 are uses with a local variable of different type (unsigned long) than 'frequency' (in drivers/sh/clk/core.c). One of these uses is safe; the other (in clk_rate_table_iter()) is broken if unsigned long is wider than unsigned int. As a side-effect, this patch corrects the potential misbehavior there.
1 is a use in macro cpufreq_for_each_entry() with what _should_ be the frequency member of a cpufreq_frequency_table, provided the caller it well-behaved. There are 18 callers of this macro; all are well-behaved. So these should also be safe.
include/linux/cpufreq.h | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index ec4112d..8f8ae95 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -482,8 +482,8 @@ extern struct cpufreq_governor cpufreq_gov_conservative; *********************************************************************/ /* Special Values of .frequency field */ -#define CPUFREQ_ENTRY_INVALID ~0 -#define CPUFREQ_TABLE_END ~1 +#define CPUFREQ_ENTRY_INVALID ~0u +#define CPUFREQ_TABLE_END ~1u /* Special Values of .flags field */ #define CPUFREQ_BOOST_FREQ (1 << 0) -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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