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    Subject[PATCH AUTOSEL 5.0 027/262] iio: adc: fix warning in Qualcomm PM8xxx HK/XOADC driver
    Date
    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 c30c002f1fef..4735f8a1ca9d 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,
    --
    2.19.1
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