On 30/08/17 19:25, Dave Jiang wrote:
> On 08/30/2017 11:18 AM, Robin Murphy wrote:
>> On 25/08/17 21:59, Dave Jiang wrote:
>>> Adding a dmaengine transaction operation that allows copy to/from a
>>> scatterlist and a flat buffer.
>>
>> Apologies if I'm late to the party, but doesn't DMA_SG already cover
>> this use-case? As far as I can see, all this does is save the caller
>> from setting up a single-entry scatterlist to describe the buffer - even
>> if such a simplified interface is justified it seems like something that
>> could be implemented as a wrapper around dmaengine_prep_dma_sg() rather
>> than the providers having to implement a whole extra callback.
>>
>
> DMA_SG is queued to be removed in 4.14. There is no in kernel consumer
> for the code.
Ah, I see, that's what I was missing. So we're effectively just
replacing that interface with a more pragmatic alternative - that makes
sense.
Thanks,
Robin.
>>>
>>> Signed-off-by: Dave Jiang <dave.ji...@intel.com>
>>> ---
>>> Documentation/dmaengine/provider.txt | 3 +++
>>> drivers/dma/dmaengine.c | 2 ++
>>> include/linux/dmaengine.h | 19 +++++++++++++++++++
>>> 3 files changed, 24 insertions(+)
>>>
>>> diff --git a/Documentation/dmaengine/provider.txt
>>> b/Documentation/dmaengine/provider.txt
>>> index a75f52f..6241e36 100644
>>> --- a/Documentation/dmaengine/provider.txt
>>> +++ b/Documentation/dmaengine/provider.txt
>>> @@ -181,6 +181,9 @@ Currently, the types available are:
>>> - Used by the client drivers to register a callback that will be
>>> called on a regular basis through the DMA controller interrupt
>>>
>>> + * DMA_MEMCPY_SG
>>> + - The device supports scatterlist to/from memory.
>>> +
>>> * DMA_PRIVATE
>>> - The devices only supports slave transfers, and as such isn't
>>> available for async transfers.
>>> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
>>> index 428b141..4d2c4e1 100644
>>> --- a/drivers/dma/dmaengine.c
>>> +++ b/drivers/dma/dmaengine.c
>>> @@ -937,6 +937,8 @@ int dma_async_device_register(struct dma_device *device)
>>> !device->device_prep_dma_memset);
>>> BUG_ON(dma_has_cap(DMA_INTERRUPT, device->cap_mask) &&
>>> !device->device_prep_dma_interrupt);
>>> + BUG_ON(dma_has_cap(DMA_MEMCPY_SG, device->cap_mask) &&
>>> + !device->device_prep_dma_memcpy_sg);
>>> BUG_ON(dma_has_cap(DMA_CYCLIC, device->cap_mask) &&
>>> !device->device_prep_dma_cyclic);
>>> BUG_ON(dma_has_cap(DMA_INTERLEAVE, device->cap_mask) &&
>>> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
>>> index 64fbd38..0c91411 100644
>>> --- a/include/linux/dmaengine.h
>>> +++ b/include/linux/dmaengine.h
>>> @@ -67,6 +67,7 @@ enum dma_transaction_type {
>>> DMA_PQ_VAL,
>>> DMA_MEMSET,
>>> DMA_MEMSET_SG,
>>> + DMA_MEMCPY_SG,
>>> DMA_INTERRUPT,
>>> DMA_PRIVATE,
>>> DMA_ASYNC_TX,
>>> @@ -692,6 +693,7 @@ struct dma_filter {
>>> * @device_prep_dma_pq_val: prepares a pqzero_sum operation
>>> * @device_prep_dma_memset: prepares a memset operation
>>> * @device_prep_dma_memset_sg: prepares a memset operation over a scatter
>>> list
>>> + * @device_prep_dma_memcpy_sg: prepares memcpy between scatterlist and
>>> buffer
>>> * @device_prep_dma_interrupt: prepares an end of chain interrupt operation
>>> * @device_prep_slave_sg: prepares a slave dma operation
>>> * @device_prep_dma_cyclic: prepare a cyclic dma operation suitable for
>>> audio.
>>> @@ -768,6 +770,10 @@ struct dma_device {
>>> struct dma_async_tx_descriptor *(*device_prep_dma_memset_sg)(
>>> struct dma_chan *chan, struct scatterlist *sg,
>>> unsigned int nents, int value, unsigned long flags);
>>> + struct dma_async_tx_descriptor *(*device_prep_dma_memcpy_sg)(
>>> + struct dma_chan *chan,
>>> + struct scatterlist *sg, unsigned int sg_nents,
>>> + dma_addr_t buf, bool to_sg, unsigned long flags);
>>> struct dma_async_tx_descriptor *(*device_prep_dma_interrupt)(
>>> struct dma_chan *chan, unsigned long flags);
>>>
>>> @@ -899,6 +905,19 @@ static inline struct dma_async_tx_descriptor
>>> *dmaengine_prep_dma_memcpy(
>>> len, flags);
>>> }
>>>
>>> +static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_memcpy_sg(
>>> + struct dma_chan *chan, struct scatterlist *sg,
>>> + unsigned int sg_nents, dma_addr_t buf, bool to_sg,
>>> + unsigned long flags)
>>> +{
>>> + if (!chan || !chan->device ||
>>> + !chan->device->device_prep_dma_memcpy_sg)
>>> + return NULL;
>>> +
>>> + return chan->device->device_prep_dma_memcpy_sg(chan, sg, sg_nents,
>>> + buf, to_sg, flags);
>>> +}
>>> +
>>> /**
>>> * dmaengine_terminate_all() - Terminate all active DMA transfers
>>> * @chan: The channel for which to terminate the transfers
>>>
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