On Tue, Jan 16, 2018 at 02:03:49PM +0100, Arnaud Pouliquen wrote:
>
>
> On 01/16/2018 01:50 PM, Dan Carpenter wrote:
> > On Tue, Jan 16, 2018 at 01:47:29PM +0100, Arnaud Pouliquen wrote:
> >> Hello Dan
> >>
> >> On 01/16/2018 12:43 PM, Dan Carpenter wrote:
> >>> Hello Arnaud Pouliquen,
> >>>
> >>> The patch eca949800d2d: "IIO: ADC: add stm32 DFSDM support for PDM
> >>> microphone" from Jan 10, 2018, leads to the following static checker
> >>> warning:
> >>>
> >>> drivers/iio/adc/stm32-dfsdm-adc.c:555 stm32_dfsdm_audio_dma_buffer_done()
> >>> warn: potential shift truncation. '0xffffff00 (0,256-4294967040) << 8'
> >>>
> >>> drivers/iio/adc/stm32-dfsdm-adc.c
> >>> 551 while (available >= indio_dev->scan_bytes) {
> >>> 552 u32 *buffer = (u32 *)&adc->rx_buf[adc->bufi];
> >>> 553
> >>> 554 /* Mask 8 LSB that contains the channel ID */
> >>> 555 *buffer = (*buffer & 0xFFFFFF00) << 8;
> >>>
> >>> Is this shift, correct? The comment just mentions that we're masking
> >>> out the low bits.
> >> Yes mask and shift are not correlated.
> >> The Mask suppresses the 8 LSB that contain ID of the channel scanned
> >> The shift is used for the 24 to 32 bits sample conversion.
> >>
> >
> > If you wanted to silence the static checker warning you could change the
> > mask to:
> >
> > *buffer = (*buffer & 0x00FFFF00) << 8;
>
> Thanks for the proposal, fill free to send the patch, otherwise i will
> add it in next patch series.
> For my personal information which static checker warns on this line?
It's some Smatch stuff that has too many false positives so I review it
but haven't published it.
regards,
dan carpenter
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