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SubjectRe: [PATCH] soundwire: qcom: use signed variable for error return
On Wed 31 Mar 02:21 CDT 2021, Vinod Koul wrote:

> We get warning for using a unsigned variable being compared to less than
> zero. The comparison is correct as it checks for errors from previous
> call to qcom_swrm_get_alert_slave_dev_num(), so we should use a signed
> variable instead.
>
> drivers/soundwire/qcom.c: qcom_swrm_irq_handler() warn: impossible
> condition '(devnum < 0) => (0-255 < 0)'
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Vinod Koul <vkoul@kernel.org>
> ---
> drivers/soundwire/qcom.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
> index b08ecb9b418c..55ed133c6704 100644
> --- a/drivers/soundwire/qcom.c
> +++ b/drivers/soundwire/qcom.c
> @@ -428,7 +428,7 @@ static irqreturn_t qcom_swrm_irq_handler(int irq, void *dev_id)
> struct qcom_swrm_ctrl *swrm = dev_id;
> u32 value, intr_sts, intr_sts_masked, slave_status;
> u32 i;
> - u8 devnum = 0;
> + s8 devnum = 0;

At least in today's linux-next qcom_swrm_get_alert_slave_dev_num()
returns an int and the code only checks to see if this is negative. So
it seems like making this a full int ensures there's no truncation etc.

And at least as written today there's no need to initialize the
variable.

Regards,
Bjorn

> int ret = IRQ_HANDLED;
>
> swrm->reg_read(swrm, SWRM_INTERRUPT_STATUS, &intr_sts);
> --
> 2.26.3
>

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