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

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Date:	Tue, 9 Apr 2013 16:58:16 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Lars-Peter Clausen <lars@...afoo.de>, Arnd Bergmann <arnd@...db.de>
Cc:	Arnd Bergmann <arnd@...db.de>, 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 Sat, Mar 30, 2013 at 09:38:54AM +0100, Lars-Peter Clausen wrote:
> On 03/29/2013 10:49 PM, Vinod Koul wrote:
> > 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? 
> 
> The devicetree tells it, or what exactly do you mean?
Is this global id? Anrd, what does the id mean in DT?
> 
> - Lars
> 
> > 
> >>
> >> 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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