Re: [RFC PATCH v3 3/5] iio: buffer: Extend DMAengine buffer interfaces to take extra sysfs attributes

[David Lechner]

On 6/16/26 9:03 PM, Marcelo Schmitt wrote:
> Some devices using DMAengine buffers are connected to extra hardware that
> allows setting how fast data is transferred to/from the buffer. However,
> those extra pieces of harwdware are external to the sensor chip such that
> supporting the transfer speed as a sensor property is a bit of an
> inaccuracy. Expand IIO DMAengine buffer interfaces to take arguments for
> extra sysfs attributes, enabling the transfer speed to be configured
> through the buffer interface.

This message is a bit confusing. It sounds like it is attempting to
control something about the DMA controller itself. But based on the
later patches, it looks like this is just so we can add arbitrary
sysfs attributes to the bufferX directory. And in this specific case,
a sampling_frequency attribute.

> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@xxxxxxxxxx>
> ---
> New patch.
> 
> Now that I've come to this buffer "solution", I have pretty much convinced
> myself it would be better to instead have some sort of IIO trigger to control
> the signal source connected to SPI offloading trigger module.
> 
In the other chips with SPI offload we've done already, we just used
IIO_CHAN_INFO_SAMP_FREQ to control the SPI offload trigger rate.
Any reason why we can't do that here? In the original SPI offload
discussions, IIRC the general consensus was that adding a trigger
just to control that was overkill when I suggested the same.