Re: [PATCH v2 1/3] dmaengine: add DMA_PREP_CMD for non-Data descriptors.

[Abhishek Sahu]

On 2017-07-19 17:48, Abhishek Sahu wrote:
> On 2017-07-19 15:37, Vinod Koul wrote:
> > On Mon, Jun 26, 2017 at 06:19:27PM +0530, Abhishek Sahu wrote:
> > > Some of the DMA controllers are capable of issuing the commands
> > > to peripheral by the DMA. These commands can be list of register
> > > reads/writes and its different from normal data reads/writes.
> > > This patch adds new flag DMA_PREP_CMD in DMA API which tells
> > > the driver that the data passed to DMA API is in command format
> > > and DMA driver will form descriptor in the required format.
> > >
> > > This flag can be used by any DMA controller driver which requires
> > > special handling for non-Data descriptors.
> >
> > Please add Documentation for this new flag in
> > Documentation/dmaengine/provider.txt
>
>  Sure. I will add update the documentation in v3.
>
> > > Signed-off-by: Abhishek Sahu <absahu@xxxxxxxxxxxxxx>
> > > ---
> > >  include/linux/dmaengine.h | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> > > index 5336808..bbc297e 100644
> > > --- a/include/linux/dmaengine.h
> > > +++ b/include/linux/dmaengine.h
> > > @@ -186,6 +186,8 @@ struct dma_interleaved_template {
> > >   *  on the result of this operation
> > >   * @DMA_CTRL_REUSE: client can reuse the descriptor and submit again 
> > > till
> > >   *  cleared or freed
> > > + * @DMA_PREP_CMD: tell the driver that the data passed to DMA API is 
> > > in command
> > > + *  format and it will be used for configuring the peripheral 
> > > registers.
> >
> > Can you explain what is command format..?
>
>  The command format is not generic and its format will be dependent
>  upon DMA engine. The client drivers will give data in its own
>  command formats and this flag will be passed to DMA APIâs to do
>  the parsing according to its own command format.
>
>  Currently this flag description and name is inclined towards
>  Qualcomm BAM DMA command flag. We want to make this flag as
>  generic one so require your suggestion regarding this.
>  Will renaming this flag as DMA_PREP_NON_DATA or
>  DMA_PREP_CUSTOM make it more generic?

 can we use same flag name DMA_PREP_CMD or should we
 go for some other name?

> > >   */
> > >  enum dma_ctrl_flags {
> > >  	DMA_PREP_INTERRUPT = (1 << 0),
> > > @@ -195,6 +197,7 @@ enum dma_ctrl_flags {
> > >  	DMA_PREP_CONTINUE = (1 << 4),
> > >  	DMA_PREP_FENCE = (1 << 5),
> > >  	DMA_CTRL_REUSE = (1 << 6),
> > > +	DMA_PREP_CMD = (1 << 7),
> > >  };


--
Abhishek Sahu