linux-kernel - Re: [PATCH 1/2] dma: of: Add generic xlate function for matching by channel id

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Date:	Sat, 30 Mar 2013 03:19:51 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Lars-Peter Clausen <lars@...afoo.de>, Arnd Bergmann <arnd@...db.de>
Cc:	Dan Williams <djbw@...com>, Jon Hunter <jon-hunter@...com>,
	Padmavathi Venna <padma.v@...sung.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dma: of: Add generic xlate function for matching
 by channel id

On Mon, Mar 25, 2013 at 02:16:51PM +0100, Lars-Peter Clausen wrote:
> This patch adds a new generic of dma xlate callback function which will match a
> channel by its id.
how will the client know which "id" to request? 

> 
> Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
> ---
>  drivers/dma/of-dma.c   | 47 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/of_dma.h |  4 ++++
>  2 files changed, 51 insertions(+)
> 
> diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
> index 00db454..7cad4d7 100644
> --- a/drivers/dma/of-dma.c
> +++ b/drivers/dma/of-dma.c
> @@ -269,3 +269,50 @@ struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
>  			&dma_spec->args[0]);
>  }
>  EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
> +
> +struct of_dma_filter_by_chan_id_args {
> +	struct dma_device *dev;
> +	unsigned int chan_id;
> +};
> +
> +static bool of_dma_filter_by_chan_id(struct dma_chan *chan, void *params)
> +{
> +	struct of_dma_filter_by_chan_id_args *args = params;
> +
> +	return chan->device == args->dev && chan->chan_id == args->chan_id;
> +}
> +
> +/**
> + * 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 want
> + * 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 uppon.
> + *
> + * 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 of_dma_filter_by_chan_id_args args;
> +	dma_cap_mask_t cap;
> +
> +	args.dev = ofdma->of_dma_data;
> +	if (!args.dev)
> +		return NULL;
> +
> +	if (dma_spec->args_count != 1)
> +		return NULL;
> +
> +	dma_cap_zero(cap);
> +	dma_cap_set(DMA_SLAVE, cap);
> +
> +	args.chan_id = dma_spec->args[0];
> +
> +	return dma_request_channel(cap, of_dma_filter_by_chan_id, &args);
> +}
> +EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);
> diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
> index ce6a8ab..46732d3 100644
> --- a/include/linux/of_dma.h
> +++ b/include/linux/of_dma.h
> @@ -43,6 +43,8 @@ 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)
> @@ -69,6 +71,8 @@ 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 */
> -- 
> 1.8.0
> 
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