[alsa-devel] [PATCH v5 06/10] dmaengine: add API for getting dma controller's quirk

Vinod Koul vinod.koul at intel.com
Wed Oct 14 03:53:10 PDT 2015

On Thu, Oct 08, 2015 at 10:31:18AM +0200, Lars-Peter Clausen wrote:
> > Basically I agree not to expose dma's quirk to slave controllers...But, the
> > fact I mentioned on cover letter explain the reasons why I have to let slave
> > controllers know that they are working with a broken dma. It's a dilemma
> > that if we don't want that to be exposed(let slave controllers' driver get
> > the info via a API), we have t add broken quirk for all of them ,here and
> > there, which seems to be a disaster:(
> The problem with this API is that it transports values with device specific
> meanings over a generic API. Which is generally speaking not a good idea
> because the consumer witch is supposed to be generic suddenly needs to know
> which provider it is talking to.
> A better solution in this case typically is either introduce a generic API
> with generic values or a custom API with custom values, but don't mix the two.
> > 
> > I would appreciate it if you could give me some suggestions at your earliest
> > convenience. :)
> In this case I think the best way to handle this is not quirks, but rather
> expose the actual maximum burst size using the DMA capabilities API. Since
> supporting only a certain burst depth is not really a quirk. All hardware
> has a limit for this and for some it might be larger or smaller than for
> others and it might be the same IP core but the maximum size depends on some
> IP core parameters. So this should be discoverable.

yes that makes more sense than adding quirks, exposing the right values
which should be a readable property for driver will ensure it works on
system with/without quirks


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