Re: [PATCH] iio: adc: nxp-sar-adc: zero-initialize dma_slave_config

[Jonathan Cameron]

On Mon, 6 Apr 2026 08:59:34 -0500
David Lechner <dlechner@xxxxxxxxxxxx> wrote:

> On 4/6/26 4:53 AM, Shuvam Pandey wrote:
> > nxp_sar_adc_start_cyclic_dma() only fills the RX-side members of
> > dma_slave_config before passing it to dmaengine_slave_config().
> > 
> > Zero-initialize the structure so unused members do not contain stack
> > garbage. Some DMA engines consult optional dma_slave_config fields, so
> > leaving them uninitialized can cause DMA setup failures.
> > 
> > Fixes: 4434072a893e ("iio: adc: Add the NXP SAR ADC support for the s32g2/3 platforms")
> > Signed-off-by: Shuvam Pandey <shuvampandey1@xxxxxxxxx>
> > ---
> >  drivers/iio/adc/nxp-sar-adc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iio/adc/nxp-sar-adc.c b/drivers/iio/adc/nxp-sar-adc.c
> > index 9efa883c277d..7d7b5a580167 100644
> > --- a/drivers/iio/adc/nxp-sar-adc.c
> > +++ b/drivers/iio/adc/nxp-sar-adc.c
> > @@ -659,7 +659,7 @@ static void nxp_sar_adc_dma_cb(void *data)
> >  static int nxp_sar_adc_start_cyclic_dma(struct iio_dev *indio_dev)
> >  {
> >  	struct nxp_sar_adc *info = iio_priv(indio_dev);
> > -	struct dma_slave_config config;
> > +	struct dma_slave_config config = {};  
> 
> IIO style is to have space between braces.
> 
> Wait and see if Jonathan asks for a new version first though
> before sending one for trivial changes like that.
> 
> >  	struct dma_async_tx_descriptor *desc;
> >  	int ret;
> >    
> 
> Reviewed-by: David Lechner <dlechner@xxxxxxxxxxxx>
> 
Note I picked this up and tweaked as above, so the following is
just thoughts on how we might do similar in future. 

It is a bigger change but maybe it's worth 

	struct dma_slave_config config;

...

	config = (struct dma_slave_config) {
		.direction = DMA_DEV_TO_MEM,
		.src_addr_width = NXP_SAR_ADC_DMA_SAMPLE_SZ,
		.src_addr = NXP_SAR_ADC_CDR(info->regs_phys, info->buffered_chan[0]),
		.src_port_window_size = info->channels_used,
		.src_maxburst = info->channels_used,
	};
Which will ensure whole thing is set at the point of use rather than clear
and then fill stuff in later as this patch does.

Given this has been sat a while, lets go for good enough and it's a more
minimal patch which is always nice for a fix.

Applied to the fixes-togreg branch of iio.git and marked for
stable.

Thanks,

Jonathan