Re: [PATCH i2c-next v9 5/5] i2c: aspeed: Add bus idle waiting logic for multi-master use cases

Jae Hyun Yoo
2018-10-30T23:04:28Z

On 10/30/2018 3:22 PM, kbuild test robot wrote:
> Hi Jae,
>
> Thank you for the patch! Perhaps something to improve:
>
> [auto build test WARNING on wsa/i2c/for-next]
> [also build test WARNING on v4.19 next-20181030]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>
> url: https://github.com/0day-ci/linux/commits/Jae-Hyun-Yoo/dt-bindings-i2c-Add-bus-timeout-ms-and-retries-properties-as-common-optional/20181031-051152
> base: https://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git i2c/for-next
> config: xtensa-allyesconfig (attached as .config)
> compiler: xtensa-linux-gcc (GCC) 8.1.0
> reproduce:
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # save the attached .config to linux build tree
> GCC_VERSION=8.1.0 make.cross ARCH=xtensa
>
> Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
> http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings
>
> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/ktime.h:25,
> from include/linux/rcutiny.h:28,
> from include/linux/rcupdate.h:209,
> from include/linux/srcu.h:33,
> from include/linux/notifier.h:16,
> from include/linux/clk.h:17,
> from drivers/i2c/busses/i2c-aspeed.c:13:
> drivers/i2c/busses/i2c-aspeed.c: In function 'aspeed_i2c_master_xfer':
>>> include/linux/jiffies.h:108:15: warning: 'timeout' may be used uninitialized in this function [-Wmaybe-uninitialized]
> ((long)((b) - (a)) < 0))
> ^
> drivers/i2c/busses/i2c-aspeed.c:607:16: note: 'timeout' was declared here
> unsigned long timeout;
> ^~~~~~~
> --
> In file included from include/linux/ktime.h:25,
> from include/linux/rcutiny.h:28,
> from include/linux/rcupdate.h:209,
> from include/linux/srcu.h:33,
> from include/linux/notifier.h:16,
> from include/linux/clk.h:17,
> from drivers/i2c//busses/i2c-aspeed.c:13:
> drivers/i2c//busses/i2c-aspeed.c: In function 'aspeed_i2c_master_xfer':
>>> include/linux/jiffies.h:108:15: warning: 'timeout' may be used uninitialized in this function [-Wmaybe-uninitialized]
> ((long)((b) - (a)) < 0))
> ^
> drivers/i2c//busses/i2c-aspeed.c:607:16: note: 'timeout' was declared here
> unsigned long timeout;
> ^~~~~~~
>
> vim +/timeout +108 include/linux/jiffies.h
>
> ^1da177e Linus Torvalds 2005-04-16 91
> ^1da177e Linus Torvalds 2005-04-16 92 /*
> ^1da177e Linus Torvalds 2005-04-16 93 * These inlines deal with timer wrapping correctly. You are
> ^1da177e Linus Torvalds 2005-04-16 94 * strongly encouraged to use them
> ^1da177e Linus Torvalds 2005-04-16 95 * 1. Because people otherwise forget
> ^1da177e Linus Torvalds 2005-04-16 96 * 2. Because if the timer wrap changes in future you won't have to
> ^1da177e Linus Torvalds 2005-04-16 97 * alter your driver code.
> ^1da177e Linus Torvalds 2005-04-16 98 *
> ^1da177e Linus Torvalds 2005-04-16 99 * time_after(a,b) returns true if the time a is after time b.
> ^1da177e Linus Torvalds 2005-04-16 100 *
> ^1da177e Linus Torvalds 2005-04-16 101 * Do this with "<0" and ">=0" to only test the sign of the result. A
> ^1da177e Linus Torvalds 2005-04-16 102 * good compiler would generate better code (and a really good compiler
> ^1da177e Linus Torvalds 2005-04-16 103 * wouldn't care). Gcc is currently neither.
> ^1da177e Linus Torvalds 2005-04-16 104 */
> ^1da177e Linus Torvalds 2005-04-16 105 #define time_after(a,b) \
> ^1da177e Linus Torvalds 2005-04-16 106 (typecheck(unsigned long, a) && \
> ^1da177e Linus Torvalds 2005-04-16 107 typecheck(unsigned long, b) && \
> 5a581b36 Paul E. McKenney 2013-07-27 @108 ((long)((b) - (a)) < 0))
> ^1da177e Linus Torvalds 2005-04-16 109 #define time_before(a,b) time_after(b,a)
> ^1da177e Linus Torvalds 2005-04-16 110
>
> :::::: The code at line 108 was first introduced by commit
> :::::: 5a581b367b5df0531265311fc681c2abd377e5e6 jiffies: Avoid undefined behavior from signed overflow
>
> :::::: TO: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> :::::: CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>
> ---
> 0-DAY kernel test infrastructure Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all Intel Corporation
>

This is a false warning.

The 'timeout' local variable will be initialized properly if it's gonna
be used when the multi-master property is set.

-Jae