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;
regards,
dan carpenter
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