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    SubjectRe: [PATCH] ASoC: Fix overflow bug in SOC_DOUBLE_R_SX_TLV
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    On Fri, 2010-06-18 at 12:56 +1000, Stuart Longland wrote:
    > When SX_TLV widgets are read, if the gain is set to a value below 0dB,
    > the mixer control is erroniously read as being at maximum volume.
    >
    > The value read out of the CODEC register is never sign-extended, and
    > when the minimum value is subtracted (read; added, since the minimum is
    > negative) the result is a number greater than the maximum allowed value
    > for the control, and hence it saturates.
    >
    > Solution: Mask the result so that it "wraps around", emulating
    > sign-extension.
    >
    > Signed-off-by: Stuart Longland <redhatter@gentoo.org>
    > ---
    > sound/soc/soc-core.c | 4 ++--
    > 1 files changed, 2 insertions(+), 2 deletions(-)
    >
    > diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
    > index a82a797..0470288 100644
    > --- a/sound/soc/soc-core.c
    > +++ b/sound/soc/soc-core.c
    > @@ -2400,8 +2400,8 @@ int snd_soc_get_volsw_2r_sx(struct snd_kcontrol *kcontrol,
    > int val = snd_soc_read(codec, mc->reg) & mask;
    > int valr = snd_soc_read(codec, mc->rreg) & mask;
    >
    > - ucontrol->value.integer.value[0] = ((val & 0xff)-min);
    > - ucontrol->value.integer.value[1] = ((valr & 0xff)-min);
    > + ucontrol->value.integer.value[0] = ((val & 0xff)-min) & mask;
    > + ucontrol->value.integer.value[1] = ((valr & 0xff)-min) & mask;
    > return 0;
    > }
    > EXPORT_SYMBOL_GPL(snd_soc_get_volsw_2r_sx);

    Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
    --
    Freelance Developer, SlimLogic Ltd
    ASoC and Voltage Regulator Maintainer.
    http://www.slimlogic.co.uk



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