Re: [alsa-devel] [PATCH v4 06/15] soundwire: add support for sdw_slave_type

[Pierre-Louis Bossart]

On 12/13/19 1:21 AM, Greg KH wrote:
> On Thu, Dec 12, 2019 at 11:04:00PM -0600, Pierre-Louis Bossart wrote:
> > Currently the bus does not have any explicit support for master
> > devices.
> >
> > First add explicit support for sdw_slave_type and error checks if this type
> > is not set.
> >
> > In follow-up patches we can add support for the sdw_md_type (md==Master
> > Device), following the Grey Bus example.
>
> How are you using greybus as an example of "master devices"?  All you
> are doing here is setting the type of the existing devices, right?

I took your advice to look at GreyBus and used the 'gb host device' as 
the model to implement the 'sdw master' add/startup/remove interfaces we 
needed.

so yes in this patch we just add a type for the slave, the interesting 
part is in the next patches.
> >   static int sdw_uevent(struct device *dev, struct kobj_uevent_env *env)
> >   {
> > -	struct sdw_slave *slave = to_sdw_slave_device(dev);
> > +	struct sdw_slave *slave;
> >   	char modalias[32];
> >   
> > -	sdw_slave_modalias(slave, modalias, sizeof(modalias));
> > +	if (is_sdw_slave(dev)) {
> > +		slave = to_sdw_slave_device(dev);
> > +
> > +		sdw_slave_modalias(slave, modalias, sizeof(modalias));
> >   
> > -	if (add_uevent_var(env, "MODALIAS=%s", modalias))
> > -		return -ENOMEM;
> > +		if (add_uevent_var(env, "MODALIAS=%s", modalias))
> > +			return -ENOMEM;
> > +	} else {
> > +		/* only Slave device type supported */
> > +		dev_warn(dev, "uevent for unknown Soundwire type\n");
> > +		return -EINVAL;
>
> Right now, this can not happen, right?
>
> Not a problem, just trying to understand the sequence of patches here...

yes this cannot happen at this point, it's more of a paranoid test. In 
theory a SoundWire solution could enable a 'monitor' device as defined 
in the standard.