linux-kernel - Re: [PATCH] dmaengine: add dma_slave_get

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Date:	Mon, 15 Jul 2013 13:21:11 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Vinod Koul <vinod.koul@...el.com>
CC:	linux-kernel@...r.kernel.org, Dan Williams <djbw@...com>,
	Matt Porter <matt@...orter.com>
Subject: Re: [PATCH] dmaengine: add dma_slave_get_caps api

On 07/15/2013 12:21 PM, Vinod Koul wrote:
> add new device callback .device_slave_caps api which can be used by clients to
> query the dma channel capablties before they program the channel. This can help
> is removing errors during the channel programming. Also add helper
> dma_slave_get_caps API
> 
> This patch folds the work done by Matt earlier
> https://patchwork.kernel.org/patch/2094891/
> 
> Signed-off-by: Vinod Koul <vinod.koul@...el.com>

Thanks, looks good to me. I already had some changes to the dmaengine PCM
driver based on Matt's patch, I'll rework them on top of this one.

- Lars

> ---
> this version
> 	changes api to include struct dma_slave_caps as arg
> 	removed burst lengths, can be added when we have users
> --
> 
>  include/linux/dmaengine.h |   44 ++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 44 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index cb286b1..3582593 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -370,6 +370,33 @@ struct dma_slave_config {
>  	unsigned int slave_id;
>  };
>  
> +/* struct dma_slave_caps - expose capabilities of a slave channel only
> + *
> + * @src_addr_widths: bit mask of src addr widths the channel supports
> + * @dstn_addr_widths: bit mask of dstn addr widths the channel supports
> + * @directions: bit mask of slave direction the channel supported
> + * 	since the enum dma_transfer_direction is not defined as bits for each
> + * 	type of direction, the dma controller should fill (1 << <TYPE>) and same
> + * 	should be checked by controller as well
> + * @cmd_pause: true, if pause and thereby resume is supported
> + * @cmd_terminate: true, if terminate cmd is supported
> + *
> + * @max_seg_nr: maximum number of SG segments supported
> + * 	0 for no maximum
> + * @max_seg_len: maximum length of a SG segment supported
> + * 	0 for no maximum
> + */
> +struct dma_slave_caps {
> +	u32 src_addr_widths;
> +	u32 dstn_addr_widths;
> +	u32 directions;
> +	bool cmd_pause;
> +	bool cmd_terminate;
> +
> +	u32 max_sg_nr;
> +	u32 max_sg_len;
> +};
> +
>  static inline const char *dma_chan_name(struct dma_chan *chan)
>  {
>  	return dev_name(&chan->dev->device);
> @@ -532,6 +559,7 @@ struct dma_tx_state {
>   *	struct with auxiliary transfer status information, otherwise the call
>   *	will just return a simple status code
>   * @device_issue_pending: push pending transactions to hardware
> + * @device_slave_caps: return the slave channel capabilities
>   */
>  struct dma_device {
>  
> @@ -597,6 +625,7 @@ struct dma_device {
>  					    dma_cookie_t cookie,
>  					    struct dma_tx_state *txstate);
>  	void (*device_issue_pending)(struct dma_chan *chan);
> +	int (*device_slave_caps)(struct dma_chan *chan, struct dma_slave_caps *caps);
>  };
>  
>  static inline int dmaengine_device_control(struct dma_chan *chan,
> @@ -670,6 +699,21 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
>  	return chan->device->device_prep_interleaved_dma(chan, xt, flags);
>  }
>  
> +static inline int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps)
> +{
> +	if (!chan || !caps)
> +		return -EINVAL;
> +
> +	/* check if the channel supports slave transactions */
> +	if (!test_bit(DMA_SLAVE, chan->device->cap_mask.bits))
> +		return -ENXIO;
> +
> +	if (chan->device->device_slave_caps)
> +		return chan->device->device_slave_caps(chan, caps);
> +
> +	return -ENXIO;
> +}
> +
>  static inline int dmaengine_terminate_all(struct dma_chan *chan)
>  {
>  	return dmaengine_device_control(chan, DMA_TERMINATE_ALL, 0);
> 

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