[alsa-devel] [PATCH v2 04/14] soundwire: Add MIPI DisCo property helpers

[Charles Keepax]

On Mon, Nov 27, 2017 at 02:48:50PM +0530, Vinod Koul wrote:
> On Mon, Nov 27, 2017 at 07:59:40AM +0000, Charles Keepax wrote:
> 
> > > > Apologies for the long and slightly vague comment, but I guess my
> > > > question is do you have a thought on how drivers should know when
> > > > it is safe to communicate with a SoundWire device?
> > > 
> > > IMO it is safe to communicate with SoundWire device when the Slave
> > > status is ATTACHED. In any case bus will report error if it is not able
> > > to communicate with SoundWire device.
> > 
> > Yeah I guess my point here is that there is currently no way in
> > this SoundWire framework for the slave driver to know if the
> > device is attached or not, unless I am missing something?  There
> > are calls by which the master can inform the framework, but
> > nothing to pass that on to the slave driver.
> 
> Nope, as Sanyog pointed out there are deterministic ways for Slave
> driver to find out. We can do that by:
>  a) check the slave->status and communicate only if status is SDW_SLAVE_ATTACHED
>  b) Implement sdw_slave_ops->update_status() which is invoked by Bus on any
>     status changes.
> 
> So to summarize, for a Slave driver during the probe, if the status is not
> SDW_SLAVE_ATTACHED it should not communicate and should implement
> sdw_slave_ops->update_status and attempt IO when this callback gets invoked
> with SDW_SLAVE_ATTACHED status.
> 
> Does that clarify and solve the problem.
> 

Ok apologies looks like this was my bad sorry for missing those.
That does indeed seem fine.

Thanks,
Charles