linux-kernel - Re: [PATCH 3/9] dmaengine: Introduce a device

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Message-ID: <20140928161333.GK1638@intel.com>
Date:	Sun, 28 Sep 2014 21:43:33 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	dmaengine@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Antoine Ténart <antoine@...e-electrons.com>,
	lars@...afoo.de
Subject: Re: [PATCH 3/9] dmaengine: Introduce a device_config callback

On Sat, Sep 27, 2014 at 10:54:39AM +0200, Maxime Ripard wrote:
> The fact that the channel configuration is done in device_control is rather
> misleading, since it's not really advertised as such, plus, the fact that the
> framework exposes a function of its own makes it not really intuitive, while
> we're losing the type checking whenever we pass that unsigned long argument.
> 
> Add a device_config callback to dma_device, with a fallback on the old
> behaviour for now for existing drivers to opt in.
This will break bisect, we have users of device_control in tree, they need
to be converted first to use wrappers and then we should introduce these

-- 
~Vinod
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> ---
>  include/linux/dmaengine.h | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index f4b71ce1a0a6..7937f81e5e2e 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -608,6 +608,8 @@ struct dma_tx_state {
>   *	The function takes a buffer of size buf_len. The callback function will
>   *	be called after period_len bytes have been transferred.
>   * @device_prep_interleaved_dma: Transfer expression in a generic way.
> + * @device_config: Pushes a new configuration to a channel, return 0 or an error
> + *	code
>   * @device_control: manipulate all pending operations on a channel, returns
>   *	zero or error code
>   * @device_tx_status: poll for transaction completion, the optional
> @@ -662,7 +664,6 @@ struct dma_device {
>  		struct scatterlist *dst_sg, unsigned int dst_nents,
>  		struct scatterlist *src_sg, unsigned int src_nents,
>  		unsigned long flags);
> -
>  	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,
> @@ -674,9 +675,11 @@ struct dma_device {
>  	struct dma_async_tx_descriptor *(*device_prep_interleaved_dma)(
>  		struct dma_chan *chan, struct dma_interleaved_template *xt,
>  		unsigned long flags);
> -	int (*device_control)(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> -		unsigned long arg);
>  
> +	int (*device_config)(struct dma_chan *chan,
> +			     struct dma_slave_config *config);
> +	int (*device_control)(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> +			      unsigned long arg);
>  	enum dma_status (*device_tx_status)(struct dma_chan *chan,
>  					    dma_cookie_t cookie,
>  					    struct dma_tx_state *txstate);
> @@ -697,6 +700,9 @@ static inline int dmaengine_device_control(struct dma_chan *chan,
>  static inline int dmaengine_slave_config(struct dma_chan *chan,
>  					  struct dma_slave_config *config)
>  {
> +	if (chan->device->device_config)
> +		return chan->device->device_config(chan, config);
> +
>  	return dmaengine_device_control(chan, DMA_SLAVE_CONFIG,
>  			(unsigned long)config);
>  }
> -- 
> 2.1.0
> 

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