On 11/1/2018 10:44 AM, 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-20181101]
[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: i386-allyesconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
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 >>):
drivers/i2c/busses/i2c-aspeed.c: In function 'aspeed_i2c_master_xfer':
drivers/i2c/busses/i2c-aspeed.c:624:210: warning: 'timeout' may be used
uninitialized in this function [-Wmaybe-uninitialized]
if (time_after(jiffies, timeout))
^
drivers/i2c/busses/i2c-aspeed.c:607:16: note: 'timeout' was declared here
unsigned long timeout;
^~~~~~~
vim +/timeout +624 drivers/i2c/busses/i2c-aspeed.c
604
605 static int aspeed_i2c_check_bus_busy(struct aspeed_i2c_bus *bus)
606 {
607 unsigned long timeout;
608
609 if (bus->multi_master) {
610 might_sleep();
611 /* Initialize it only when multi_master is set */
612 timeout = jiffies + bus->adap.timeout;
The 'timeout' variable will be initialized only when bus->multi_master
is true to save some OPs in case this variable isn't used. The saved OPs
are not expensive but it makes a meaning because this function is called
very frequently on every master transfer.
613 }
614
615 for (;;) {
616 if (!(readl(bus->base + ASPEED_I2C_CMD_REG) &
617 ASPEED_I2CD_BUS_BUSY_STS))
618 #if IS_ENABLED(CONFIG_I2C_SLAVE)
619 if (bus->slave_state == ASPEED_I2C_SLAVE_STOP)
620 #endif
621 return 0;
622 if (!bus->multi_master)
623 break;
If bus->multi_master is false then it doesn't fall through so the
'timeout' variable in below will not be used when itself is
uninitialized. Also, bus->multi_master is fixed at probing time and it
doesn't change at runtime so the warning case never happens.
-Jae
> 624 if (time_after(jiffies, timeout))
625 break;
626 usleep_range((ASPEED_I2C_BUS_BUSY_CHECK_INTERVAL_US >>
2) + 1,
627 ASPEED_I2C_BUS_BUSY_CHECK_INTERVAL_US);
628 }
629
630 return aspeed_i2c_recover_bus(bus);
631 }
632
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