Re: [PATCH v4 01/11] ASoC: SOF: core: add 'no_wq' probe and remove callbacks

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

> What we have atm:
> snd_sof_probe - might be called from wq
> snd_sof_remove - might be called from wq (cleans up the snd_sof_probe
> 		 step)

I don't think it's correct, snd_sof_remove cannot be called from a wq.
The device core knows nothing about workqueues.

> We want a callbacks for hardware/device probing, right, split the
> snd_sof_probe (and remove) to be able to support a sane level of
> deferred probing support.
> 
> With that in mind:
> snd_sof_device_probe - Not called from wq (to handle deferred probing)
> snd_sof_probe - might be called from wq
> 
> snd_sof_remove - might be called from wq (cleans up the snd_sof_probe
> 		 step)
> snd_sof_device_remove - Not called from wq (to up the
> 			snd_sof_device_probe step)
> 
> Naming option: s/device/hardware

I like the 'device' hint since it's directly related to the device (or
subsystem) callbacks.

> However, I think the snd_sof_device_remove itself is redundant and we
> might not need it at all as in case we have wq and there is a failure in
> there we do want to release resources as much as possible. The module
> will be kept loaded (no deferred handling in wq) and that might block
> PM, other devices to behave correctly. Iow, if the wq has failure we
> should do a cleanup to the best effort to reach a level like the driver
> is not even loaded.

If we have a failure in a workqueue used for probe, then we have to
clean-up everything since nothing in the device core will do so for us.