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

Abhishek Sahu
2017-07-28T16:09:00Z

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@codeaurora.org>
>>> ---
>>> 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 API’s 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