[PATCH] spi: lp-8841: return correct error code from probe

[PATCH] spi: lp-8841: return correct error code from probe

[Arnd Bergmann]

The spi_lp8841_rtc_probe() function misses an initialization of the
return code when it fails to get its memory resource, as gcc notices:

drivers/spi/spi-lp8841-rtc.c: In function 'spi_lp8841_rtc_probe':
drivers/spi/spi-lp8841-rtc.c:239:9: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This changes the code to propagate the error from devm_ioremap_resource().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 7ecbfff6711f ("spi: master driver to enable RTC on ICPDAS LP-8841")
---
 drivers/spi/spi-lp8841-rtc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-lp8841-rtc.c b/drivers/spi/spi-lp8841-rtc.c
index 44bb69c3f1d6..faa577d282c0 100644
--- a/drivers/spi/spi-lp8841-rtc.c
+++ b/drivers/spi/spi-lp8841-rtc.c
@@ -217,8 +217,9 @@ spi_lp8841_rtc_probe(struct platform_device *pdev)
 	data = spi_master_get_devdata(master);
 
 	iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	data->iomem =  devm_ioremap_resource(&pdev->dev, iomem);
-	if (IS_ERR(data->iomem)) {
+	data->iomem = devm_ioremap_resource(&pdev->dev, iomem);
+	ret = PTR_ERR_OR_ZERO(data->iomem);
+	if (ret) {
 		dev_err(&pdev->dev, "failed to get IO address\n");
 		goto err_put_master;
 	}
-- 
2.7.0

[PATCH] spi: lp-8841: return correct error code from probe

[Sergei Ianovich]

On Thu, 2016-02-25 at 12:37 +0100, Arnd Bergmann wrote:
> The spi_lp8841_rtc_probe() function misses an initialization of the
> return code when it fails to get its memory resource, as gcc notices:
> 
> drivers/spi/spi-lp8841-rtc.c: In function 'spi_lp8841_rtc_probe':
> drivers/spi/spi-lp8841-rtc.c:239:9: error: 'ret' may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
> 
> This changes the code to propagate the error from
> devm_ioremap_resource().
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 7ecbfff6711f ("spi: master driver to enable RTC on ICPDAS LP-
> 8841")

Tested-by: Sergei Ianovich <ynvich@gmail.com>

[PATCH] spi: lp-8841: return correct error code from probe

[Sergei Ianovich]

Hi?Arnd,

On Thu, 2016-02-25 at 12:37 +0100, Arnd Bergmann wrote:
> The spi_lp8841_rtc_probe() function misses an initialization of the
> return code when it fails to get its memory resource, as gcc notices:
> 
> drivers/spi/spi-lp8841-rtc.c: In function 'spi_lp8841_rtc_probe':
> drivers/spi/spi-lp8841-rtc.c:239:9: error: 'ret' may be used
> uninitialized in this function [-Werror=maybe-uninitialized]

I wasn't getting this warning when I was building the driver. This
happened because -Wmaybe-uninitialized is suppressed when
CONFIG_CC_OPTIMIZE_FOR_SIZE is selected
(Commit?e74fc973b6e531fef1fce8b101ffff05ecfb774c "Turn off -Wmaybe-
uninitialized when building with -Os").

A recent gcc version like 5.3.1 doesn't seem to produce much false
positives. May it make sense to revert that commit?

The gcc-5.3.1 log for reference.

---8<---
$ arm-linux-gnueabi-gcc --version
arm-linux-gnueabi-gcc (Debian 5.3.1-8) 5.3.1 20160205
$ make -j 4 -s KCFLAGS=-Wmaybe-uninitialized
ipc/shm.c: In function 'SyS_shmdt':
ipc/shm.c:1344:59: warning: 'file' may be used uninitialized in this function [-Wmaybe-uninitialized]
???????((vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff) &&
???????????????????????????????????????????????????????????^
ipc/shm.c:1267:15: note: 'file' was declared here
? struct file *file;
???????????????^
mm/vmscan.c: In function 'shrink_zone':
mm/vmscan.c:2418:18: warning: 'lru_pages' may be used uninitialized in this function [-Wmaybe-uninitialized]
????unsigned long lru_pages;
??????????????????^
drivers/gpio/gpiolib-of.c: In function 'of_gpiochip_add':
drivers/gpio/gpiolib-of.c:221:7: warning: 'dflags' may be used uninitialized in this function [-Wmaybe-uninitialized]
???if (gpiod_hog(desc, name, lflags, dflags))
???????^
drivers/gpio/gpiolib-of.c:211:19: note: 'dflags' was declared here
? enum gpiod_flags dflags;
???????????????????^
drivers/gpio/gpiolib-of.c:221:7: warning: 'lflags' may be used uninitialized in this function [-Wmaybe-uninitialized]
???if (gpiod_hog(desc, name, lflags, dflags))
???????^
drivers/gpio/gpiolib-of.c:210:25: note: 'lflags' was declared here
? enum gpio_lookup_flags lflags;
?????????????????????????^
net/core/dev.c: In function 'validate_xmit_skb_list':
net/core/dev.c:2984:15: warning: 'tail' may be used uninitialized in this function [-Wmaybe-uninitialized]
????tail->next = skb;
???????????????^
drivers/spi/spi-lp8841-rtc.c: In function 'spi_lp8841_rtc_probe':
drivers/spi/spi-lp8841-rtc.c:239:9: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
? return ret;
?????????^
net/sunrpc/svcauth_unix.c: In function 'unix_gid_parse':
net/sunrpc/svcauth_unix.c:510:2: warning: 'gids' may be used uninitialized in this function [-Wmaybe-uninitialized]
? for (i = 0 ; i < gids ; i++) {
? ^
In file included from include/linux/sunrpc/svcauth.h:16:0,
?????????????????from include/linux/sunrpc/svc.h:18,
?????????????????from include/linux/sunrpc/svcsock.h:12,
?????????????????from net/sunrpc/svcauth_unix.c:6:
include/linux/sunrpc/cache.h:306:9: warning: 'rv' may be used uninitialized in this function [-Wmaybe-uninitialized]
? return rv - boot.tv_sec;
?????????^
include/linux/sunrpc/cache.h:298:9: note: 'rv' was declared here
? time_t rv;
?????????^
net/sunrpc/svcauth_unix.c: In function 'ip_map_parse':
include/linux/sunrpc/cache.h:306:9: warning: 'rv' may be used uninitialized in this function [-Wmaybe-uninitialized]
? return rv - boot.tv_sec;
?????????^
include/linux/sunrpc/cache.h:298:9: note: 'rv' was declared here
? time_t rv;
?????????^
In file included from net/sunrpc/cache.c:34:0:
net/sunrpc/cache.c: In function 'write_flush':
include/linux/sunrpc/cache.h:306:9: warning: 'rv' may be used uninitialized in this function [-Wmaybe-uninitialized]
? return rv - boot.tv_sec;
?????????^
include/linux/sunrpc/cache.h:298:9: note: 'rv' was declared here
? time_t rv;
?????????^
net/sunrpc/auth_gss/svcauth_gss.c: In function 'rsc_parse':
net/sunrpc/auth_gss/svcauth_gss.c:456:22: warning: 'id' may be used uninitialized in this function [-Wmaybe-uninitialized]
???rsci.cred.cr_uid = make_kuid(&init_user_ns, id);
??????????????????????^
In file included from include/linux/sunrpc/svcauth.h:16:0,
?????????????????from include/linux/sunrpc/svc.h:18,
?????????????????from include/linux/sunrpc/auth_gss.h:17,
?????????????????from net/sunrpc/auth_gss/svcauth_gss.c:46:
include/linux/sunrpc/cache.h:306:9: warning: 'rv' may be used uninitialized in this function [-Wmaybe-uninitialized]
? return rv - boot.tv_sec;
?????????^
include/linux/sunrpc/cache.h:298:9: note: 'rv' was declared here
? time_t rv;
?????????^
net/sunrpc/auth_gss/svcauth_gss.c: In function 'rsi_parse':
include/linux/sunrpc/cache.h:306:9: warning: 'rv' may be used uninitialized in this function [-Wmaybe-uninitialized]
? return rv - boot.tv_sec;
?????????^
include/linux/sunrpc/cache.h:298:9: note: 'rv' was declared here
? time_t rv;
?????????^
---8<---

[PATCH] spi: lp-8841: return correct error code from probe

[Arnd Bergmann]

On Saturday 27 February 2016 22:32:57 Sergei Ianovich wrote:
> Hi Arnd,
> 
> On Thu, 2016-02-25 at 12:37 +0100, Arnd Bergmann wrote:
> > The spi_lp8841_rtc_probe() function misses an initialization of the
> > return code when it fails to get its memory resource, as gcc notices:
> > 
> > drivers/spi/spi-lp8841-rtc.c: In function 'spi_lp8841_rtc_probe':
> > drivers/spi/spi-lp8841-rtc.c:239:9: error: 'ret' may be used
> > uninitialized in this function [-Werror=maybe-uninitialized]
> 
> I wasn't getting this warning when I was building the driver. This
> happened because -Wmaybe-uninitialized is suppressed when
> CONFIG_CC_OPTIMIZE_FOR_SIZE is selected
> (Commit e74fc973b6e531fef1fce8b101ffff05ecfb774c "Turn off -Wmaybe-
> uninitialized when building with -Os").
> 
> A recent gcc version like 5.3.1 doesn't seem to produce much false
> positives. May it make sense to revert that commit?
> 
> The gcc-5.3.1 log for reference.

I have spent a lot of time on fixing those warning messages. I still
see tons of warnings even with the latest compilers when -Os (all
false positives) is used, and I have a branch in which I have fixed
all the ones that happen when building with -O2.

I recently submitted a patch to turn CONFIG_CC_OPTIMIZE_FOR_SIZE
into a choice statement that is not automatically set on an
allmodconfig build, which should help here, but my patch has
not yet been merged.

We have similar problems with a couple of other options that
drastically increase the false positive rate for these warnings
(GCOV_PROFILE_ALL, PROFILE_ALL_BRANCHES, UBSAN_SANTIZE_ALL, ...),
and I think our best strategy for all of these is to make sure
they are not enabled in an allmodconfig build or the typical
defconfigs, but also to hide the warnings if they are used in
a particular config.

	Arnd