Re: [PATCH RFC v12 5/7] dma: of: add common xlate function for matching by channel id

[Vinod Koul <vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Wed, Apr 23, 2014 at 05:53:27PM +0400, Alexander Popov wrote:
> This patch adds a new common OF dma xlate callback function which will match a
> channel by it's id. The binding expects one integer argument which it will use to
> lookup the channel by the id.
> 
> Unlike of_dma_simple_xlate this function is able to handle a system with
> multiple DMA controllers. When registering the of dma provider with
> of_dma_controller_register a pointer to the dma_device struct which is
> associated with the dt node needs to passed as the data parameter.
> New function will use this pointer to match only channels which belong to the
> specified DMA controller.

This patch needs review by DT folks too

> 
> Signed-off-by: Alexander Popov <a13xp0p0v88-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  drivers/dma/of-dma.c   | 35 +++++++++++++++++++++++++++++++++++
>  include/linux/of_dma.h |  4 ++++
>  2 files changed, 39 insertions(+)
> 
> diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
> index e8fe9dc..d5fbeaa 100644
> --- a/drivers/dma/of-dma.c
> +++ b/drivers/dma/of-dma.c
> @@ -218,3 +218,38 @@ struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
>  			&dma_spec->args[0]);
>  }
>  EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
> +
> +/**
> + * of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
> + * @dma_spec:	pointer to DMA specifier as found in the device tree
> + * @of_dma:	pointer to DMA controller data
> + *
> + * This function can be used as the of xlate callback for DMA driver which wants
> + * to match the channel based on the channel id. When using this xlate function
> + * the #dma-cells propety of the DMA controller dt node needs to be set to 1.
> + * The data parameter of of_dma_controller_register must be a pointer to the
> + * dma_device struct the function should match upon.
> + *
> + * Returns pointer to appropriate dma channel on success or NULL on error.
> + */
> +struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
> +					 struct of_dma *ofdma)
> +{
> +	struct dma_device *dev = ofdma->of_dma_data;
> +	struct dma_chan *chan, *candidate = NULL;
> +
> +	if (!dev || dma_spec->args_count != 1)
> +		return NULL;
> +
> +	list_for_each_entry(chan, &dev->channels, device_node)
> +		if (chan->chan_id == dma_spec->args[0]) {
> +			candidate = chan;
> +			break;
> +		}
> +
> +	if (!candidate)
> +		return NULL;
> +
> +	return dma_get_slave_channel(candidate);
> +}
> +EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);
> diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
> index ae36298..56bc026 100644
> --- a/include/linux/of_dma.h
> +++ b/include/linux/of_dma.h
> @@ -41,6 +41,8 @@ extern struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
>  						     const char *name);
>  extern struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
>  		struct of_dma *ofdma);
> +extern struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
> +		struct of_dma *ofdma);
>  #else
>  static inline int of_dma_controller_register(struct device_node *np,
>  		struct dma_chan *(*of_dma_xlate)
> @@ -66,6 +68,8 @@ static inline struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_s
>  	return NULL;
>  }
>  
> +#define of_dma_xlate_by_chan_id NULL
> +
>  #endif
>  
>  #endif /* __LINUX_OF_DMA_H */
> -- 
> 1.8.4.2
> 

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