Re: [PATCH v5 06/16] spi: add offload TX/RX streaming APIs

[Jonathan Cameron <jic23@xxxxxxxxxx>]

On Sun, 24 Nov 2024 11:54:44 -0600
David Lechner <dlechner@xxxxxxxxxxxx> wrote:

> On 11/24/24 10:50 AM, Jonathan Cameron wrote:
> > On Fri, 15 Nov 2024 14:18:45 -0600
> > David Lechner <dlechner@xxxxxxxxxxxx> wrote:
> >   
> >> Most configuration of SPI offloads is handled opaquely using the offload
> >> pointer that is passed to the various offload functions. However, there
> >> are some offload features that need to be controlled on a per transfer
> >> basis.
> >>
> >> This patch adds a flag field to struct spi_transfer to allow specifying
> >> such features. The first feature to be added is the ability to stream
> >> data to/from a hardware sink/source rather than using a tx or rx buffer.
> >> Additional flags can be added in the future as needed.
> >>
> >> A flags field is also added to the offload struct for providers to
> >> indicate which flags are supported. This allows for generic checking of
> >> offload capabilities during __spi_validate() so that each offload
> >> provider doesn't have to implement their own validation.
> >>
> >> As a first users of this streaming capability, getter functions are
> >> added to get a DMA channel that is directly connected to the offload.
> >> Peripheral drivers will use this to get a DMA channel and configure it
> >> to suit their needs.
> >>
> >> Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>  
> > Some docs that need updating.  Otherwise I wonder if we should delay
> > the _tx variants until there is a driver using them.
> > 
> > I'm sure you have one on the way and there is an argument that it makes
> > sense to review rx and tx together, but still good to only add code
> > when it's used.
> > 
> > Jonathan
> >   
> 
> In v1 Mark commented that he expected TX along with RX. And we do
> have a DAC driver we can probably add to the series in the next
> revision that uses it.
Perfect, or maybe just reference that in the description as
'coming soon'.  I'm fine with infrastructure coming a bit before the
user and I can always trust you to send me more drivers :)

Jonathan