On Tue, Mar 03, 2015 at 12:09:14PM +0200, Jyri Sarha wrote: > On 03/02/2015 09:58 PM, Lars-Peter Clausen wrote: > >Can you include a description why this is needed and how and when it is > >supposed to be used? > Would this addition do: > ------------------------------------------------------------ > These constraints help to disable the sample-format and sample-rate > combinations that do not properly work on a specific HW. > ------------------------------------------------------------ Not entirely... > The reason why we need these is coming from limitations in McASP clock > generation. With a simple divider one can only produce certain bit-clocks. > With those bit-clocks we can only play/capture some sample-rate and > sample-width combinations accurately. > The McASP driver could try to set the constraints automatically. However, > since the constraint code can not select sample-width and sample-rate > combinations there is a compromise to be made between them. Making such > compromises automatically does not usually work that well. ...this is more the point. Perhaps the constraints language needs improvement here? > In our case these properties could of course be added to McASP driver, but > then again I would expect that there is a wider need for this kind of > functionality. And it may not always be clear if either end of the link > alone is responsible for less than perfect operation. The trouble with this sort of interface is that it's a quick and dirty way for people to bodge around things rather than actually fixing them properly. Of course sometimes fixing things properly is really hard and that means we want a temporary bodge but having to put them in DT is really unfortunate.
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