DMA_ENGINE: can't use it without selecting a dma engine driver

DMA_ENGINE: can't use it without selecting a dma engine driver

[Dragos Tatulea]

Hi,

	Just discovered that it's impossible to select the dma engine without
	compiling a dma engine driver from the kernel. What if I want to use a
	different dma engine?
 
	I'm using CONFIG_DMADEVICES=y CONFIG_DMA_ENGINE=y (dependencies
	included),	

Thanks,
Dragos

Re: DMA_ENGINE: can't use it without selecting a dma engine driver

[Dan Williams]

On Tue, Jun 16, 2009 at 2:53 PM, Dragos Tatulea<dtatulea@ixiacom.com> wrote:
> Hi,
>
>        Just discovered that it's impossible to select the dma engine without
>        compiling a dma engine driver from the kernel. What if I want to use a
>        different dma engine?
>

Create a Kconfig entry for your driver in drivers/dma/Kconfig and have
it "select DMA_ENGINE".

Re: DMA_ENGINE: can't use it without selecting a dma engine driver

[Dragos Tatulea]

Hi,

> >
> >        Just discovered that it's impossible to select the dma engine
> > without compiling a dma engine driver from the kernel. What if I want to
> > use a different dma engine?
> >
> 
> Create a Kconfig entry for your driver in drivers/dma/Kconfig and have
> it "select DMA_ENGINE".
That's what I want to avoid. The dma engine driver is out of tree.

What is the rationale behind this? It seems (to me) impossible to have all
such drivers in upstream.

Thanks,
Dragos

Re: DMA_ENGINE: can't use it without selecting a dma engine driver

[Dan Williams]

Dragos Tatulea wrote:
> Hi,
> 
>>>        Just discovered that it's impossible to select the dma engine
>>> without compiling a dma engine driver from the kernel. What if I want to
>>> use a different dma engine?
>>>
>> Create a Kconfig entry for your driver in drivers/dma/Kconfig and have
>> it "select DMA_ENGINE".
> That's what I want to avoid. The dma engine driver is out of tree.
> 
> What is the rationale behind this? It seems (to me) impossible to have all
> such drivers in upstream.

It is very straightforward to have all drivers upstream, just send the 
code [1].

The rationale for this configuration scheme is to turn off a lot of 
unnecessary code when we know at build time that a dma driver will never 
be loaded.

If you must keep your driver out of tree simply maintain another out of 
tree patch that allows DMA_ENGINE to be manually enabled.

Regards,
Dan

[1]: http://www.kernel.org/doc/Documentation/SubmittingDrivers