Re: [RFC PATCH 07/16] soundwire: bus: add API for BPT protocol

[Charles Keepax <ckeepax@opensource.cirrus.com>]

On Mon, Dec 18, 2023 at 02:12:36PM +0100, Pierre-Louis Bossart wrote:
> > Is this a protocol requirement?
> 
> No, it's an implementation requirement.
> 
> We could move this to host-specific parts but then the codec drivers
> will have to know about alignment requirements for each host they are
> use with. IOW, it's more work for codec drivers if we don't have a
> minimum bar for alignment requirement across all platforms.
> 

I do certainly see that side of the argument and it does probably
warrant some thought as to how a slave might learn the alignment
requirements. I guess maybe some sort of core helper function to
return the alignment? Or putting it in properties the slave can
access? One could even keep the check here, but just pull the
value from something system specific.

The danger with putting it in the core is IMHO:

a) It rules out certain use-cases, generally I think its a bad
idea if the framework design prohibits stuff the underlying bus
could do because someone will, at some point, want to do it.

b) The core limit could get a bit out of hand once more
controllers are added. The core limit needs to be a multiple of
all the controller limits, if a controller comes along with a
weird alignment requirement, that gets problematic fast.

Thanks,
Charles