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SubjectRe: [RFC] dmaengine/dma_slave: add context parameter to prep_slave_sg callback
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On Thu, 2012-01-26 at 16:22 -0500, Alexandre Bounine wrote:
> As we agreed during our discussion about adding DMA Engine support for RapidIO
> subsystem, RapidIO and similar clients may benefit from adding an extra context
> parameter to device_prep_slave_sg() callback.
> See https://lkml.org/lkml/2011/10/24/275 for more details.
>
> Adding the context parameter will allow to pass client/target specific
> information associated with an individual data transfer request.
>
> In the case of RapidIO support this additional information consists of target
> destination ID and its buffer address (which is not mapped into the local CPU
> memory space). Because a single RapidIO-capable DMA channel may queue data
> transfer requests to different target devices, the per-request configuration
> is required.
>
> The proposed change eliminates need for new subsystem-specific API.
> Existing DMA_SLAVE clients will ignore the new parameter.
>
> This RFC only demonstrates the API change and does not include corresponding
> changes to existing DMA_SLAVE clients. Complete set of patches will be provided
> after (if) this API change is accepted.
This looks good to me. But was thinking if we need to add this new
parameter for other slave calls (circular, interleaved, memcpy...)

>
> Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
> Cc: Jassi Brar <jaswinder.singh@linaro.org>
> Cc: Russell King <rmk@arm.linux.org.uk>
> Cc: Kumar Gala <galak@kernel.crashing.org>
> Cc: Matt Porter <mporter@kernel.crashing.org>
> Cc: Li Yang <leoli@freescale.com>
> ---
> include/linux/dmaengine.h | 7 ++++---
> 1 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 679b349..79d71bb 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -575,7 +575,7 @@ struct dma_device {
> struct dma_async_tx_descriptor *(*device_prep_slave_sg)(
> struct dma_chan *chan, struct scatterlist *sgl,
> unsigned int sg_len, enum dma_transfer_direction direction,
> - unsigned long flags);
> + unsigned long flags, void *context);
> struct dma_async_tx_descriptor *(*device_prep_dma_cyclic)(
> struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
> size_t period_len, enum dma_transfer_direction direction);
> @@ -607,12 +607,13 @@ static inline int dmaengine_slave_config(struct dma_chan *chan,
>
> static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_single(
> struct dma_chan *chan, void *buf, size_t len,
> - enum dma_transfer_direction dir, unsigned long flags)
> + enum dma_transfer_direction dir, unsigned long flags, void *context)
> {
> struct scatterlist sg;
> sg_init_one(&sg, buf, len);
>
> - return chan->device->device_prep_slave_sg(chan, &sg, 1, dir, flags);
> + return chan->device->device_prep_slave_sg(chan, &sg, 1, dir, flags,
> + context);
> }
>
> static inline int dmaengine_terminate_all(struct dma_chan *chan)


--
~Vinod



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