Re: [PATCH v3 2/3] iio: accel: bmc150: use DMA-safe buffers for regmap bulk reads

[Jonathan Cameron]

On Thu, 27 Aug 2026 10:05:19 +0300
Andy Shevchenko <andriy.shevchenko@xxxxxxxxx> wrote:

> On Tue, Aug 25, 2026 at 02:21:55PM +0530, Yash Suthar wrote:
> > The FIFO and read_raw buffers are passed to regmap bulk/raw reads,
> > which is not DMA-safe. Moved them into struct bmc150_accel_data
> > after scan, each buffer are protected by mutex, placing them
> > after ensure DMA safety.  
> 
> ...
> 
> >  		j = 0;
> >  		iio_for_each_active_channel(indio_dev, bit)
> > -			memcpy(&data->scan.channels[j++], &buffer[i * 3 + bit],
> > +			memcpy(&data->scan.channels[j++],
> > +			       &data->fifo_buff[i * 3 + bit],
> >  			       sizeof(data->scan.channels[0]));  
> 
> While this works, I find a bit confusing usage of [j++] and [0] together.
> 
> IIUC the below is an equivalent
> 
> 		iio_for_each_active_channel(indio_dev, bit) {
> 			__le16 *val = &data->scan.channels[j++];
> 
> 			memcpy(val, &data->fifo_buff[i * 3 + bit], sizeof(val));
> 		}

This bit I fully agree with. Much more readable.
> 
> and if go further we may use asm/byteorder.h macros instead of plain memcpy().
> 
Here I'm lost.  We are just moving little endian values around.

For that matter if it is a single value, why can't see just assign it?

		iio_for_each_active_channel(indio_dev, bit)
			data->scan.channels[j++] = data->fifo_buf[i * 3 + bit];




> ...
> 
> Maybe this is for a separate change, I dunno. I leave it to others to decide.
>