[RFC,2/5] dmaengine: Add function to request slave channel from a dma_device

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

On 2018-10-09 14:22, Peter Ujfalusi wrote:
> 
> 
> On 2018-10-09 13:49, Vinod wrote:
>> On 24-09-18, 16:00, Peter Ujfalusi wrote:
>>> dma_get_any_slave_channel() would skip using the filter function, which
>>> in some cases needed to be executed before the alloc_chan_resources
>>> callback to make sure that all parameters are provided for the slave
>>> channel.
>>
>> Another request API, i though you had solved that last time around :(
> 
> Yes, I thought so, but this time it is different.
> I want to drop this patch myself also, but I need to figure out a way to
> do what the dmadev_get_slave_channel() allows me to do.
> 
> In path 4, udma_of_xlate() and the udma_dma_filter_fn()
> 
> It might be possible that I look up a free udma_chan, do the setup via
> the filter_fn() and finally call the dma_get_slave_channel().
> Might work fine, but I wanted to avoid to implement my own find free
> channel code when we have it already in DMAengine core.

It is going to be racy against parallel channel requests, but

>>> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
>>> index 16c9d021988a..32010c6ae13a 100644
>>> --- a/include/linux/dmaengine.h
>>> +++ b/include/linux/dmaengine.h
>>> @@ -1542,6 +1542,8 @@ void dma_async_device_unregister(struct dma_device *device);
>>>  void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
>>>  struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
>>>  struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
>>> +struct dma_chan *dmadev_get_slave_channel(struct dma_device *device,
>>> +					  dma_filter_fn fn, void *fn_param);

-struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
+struct dma_chan *dmadev_get_slave_channel(struct dma_device *device,
 				dma_filter_fn fn, void *fn_param);
+#define dma_get_any_slave_channel(device)\
	 dmadev_get_slave_channel(device, NULL, NULL)

Should cut down on duplicated code at least.


>>>  #define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
>>>  #define dma_request_slave_channel_compat(mask, x, y, dev, name) \
>>>  	__dma_request_slave_channel_compat(&(mask), x, y, dev, name)
>>> -- 
>>> Peter
>>>
>>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>>
> 
> - Péter
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> 

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki