From: Linus Torvalds torvalds@linux-foundation.org
[ Upstream commit e0f0ae838a25464179d37f355d763f9ec139fc15 ]
The pm8xxx_get_channel() implementation is unclear, and causes gcc to suddenly generate odd warnings. The trigger for the warning (at least for me) was the entirely unrelated commit 79a4e91d1bb2 ("device.h: Add __cold to dev_<level> logging functions"), which apparently changes gcc code generation in the caller function enough to cause this:
drivers/iio/adc/qcom-pm8xxx-xoadc.c: In function ‘pm8xxx_xoadc_probe’: drivers/iio/adc/qcom-pm8xxx-xoadc.c:633:8: warning: ‘ch’ may be used uninitialized in this function [-Wmaybe-uninitialized] ret = pm8xxx_read_channel_rsv(adc, ch, AMUX_RSV4, ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ &read_nomux_rsv4, true); ~~~~~~~~~~~~~~~~~~~~~~~ drivers/iio/adc/qcom-pm8xxx-xoadc.c:426:27: note: ‘ch’ was declared here struct pm8xxx_chan_info *ch; ^~
because gcc for some reason then isn't able to see that the termination condition for the "for( )" loop in that function is also the condition for returning NULL.
So it's not _actually_ uninitialized, but the function is admittedly just unnecessarily oddly written.
Simplify and clarify the function, making gcc also see that it always returns a valid initialized value.
Cc: Joe Perches joe@perches.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Andy Gross andy.gross@linaro.org Cc: David Brown david.brown@linaro.org Cc: Jonathan Cameron jic23@kernel.org Cc: Hartmut Knaack knaack.h@gmx.de Cc: Lars-Peter Clausen lars@metafoo.de Cc: Peter Meerwald-Stadler pmeerw@pmeerw.net Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iio/adc/qcom-pm8xxx-xoadc.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/drivers/iio/adc/qcom-pm8xxx-xoadc.c b/drivers/iio/adc/qcom-pm8xxx-xoadc.c index b093ecddf1a8..54db848f0bcd 100644 --- a/drivers/iio/adc/qcom-pm8xxx-xoadc.c +++ b/drivers/iio/adc/qcom-pm8xxx-xoadc.c @@ -423,18 +423,14 @@ static irqreturn_t pm8xxx_eoc_irq(int irq, void *d) static struct pm8xxx_chan_info * pm8xxx_get_channel(struct pm8xxx_xoadc *adc, u8 chan) { - struct pm8xxx_chan_info *ch; int i;
for (i = 0; i < adc->nchans; i++) { - ch = &adc->chans[i]; + struct pm8xxx_chan_info *ch = &adc->chans[i]; if (ch->hwchan->amux_channel == chan) - break; + return ch; } - if (i == adc->nchans) - return NULL; - - return ch; + return NULL; }
static int pm8xxx_read_channel_rsv(struct pm8xxx_xoadc *adc,