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 09:38:54 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Vinod Koul <vinod.koul@...el.com>
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 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?

- 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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