Re: [PATCH] ASoC: Intel: Unify HDAudio-ext bus initialization

[Cezary Rojewski <cezary.rojewski@intel.com>]

On 2021-10-19 8:42 PM, Pierre-Louis Bossart wrote:
> On 10/19/21 12:32 PM, Cezary Rojewski wrote:
>> On 2021-10-19 6:58 PM, Pierre-Louis Bossart wrote:

...

>>> I am not opposed to updates in this hdaudio-ext part, but I am in favor
>>> of less ambitious step-by-step changes.
>>>
>>> a) This is legacy code where the initial authors have moved on, and it's
>>> very hard to figure out what the intent was. It's quite common to have
>>> discussion on feature v. bug, see e.g. the discussion we had on this in
>>> https://github.com/thesofproject/linux/pull/3175#pullrequestreview-772674119
>>>
>>>
>>> b) In addition, this code is shared between two teams with separate
>>> testing/CI capabilities and limited number of commercial/shipping
>>> devices. There is a very large risk of introducing bugs even with the
>>> best intentions.
>>>
>>> Before we do any changes in functionality, there are already basic steps
>>> that can be done, e.g. using consistent naming between variables, the
>>> existing code is just confusing as can be:
>>>
>>> struct hdac_stream *stream;
>>> struct hdac_ext_stream *stream;
>>> struct hdac_stream *hstream;
>>> struct hdac_ext_stream *hstream;
>>>
>>> I started basic cleanups here:
>>> https://github.com/thesofproject/linux/pull/3158, I haven't had time to
>>> complete this because of more important locking issues, but I intend to
>>> send those clarifications for the next cycle.
>>>
>>> Again before we do large changes let's think of smaller steps and how we
>>> are going to validate those changes.
>>
>> Agree, step-by-step is the way to go.
>>
>> Isn't this patch a 'step' though? This isn't remotely a refactor, just
>> gathering of common parts of ext-bus initialization. We could start with
>> this so legacy users are unaffected, then have snd_hdac_bus_init()
>> updated so snd_hdac_ext_bus_init() is devoid of 'core' fields
>> assignments as suggested by Kai.
> 
> If it was just moving common parts, I would have no issue. My main
> objection is that you went one step further and started renaming stuff
> in rather confusing ways, e.g.
> 
> -void sof_hda_bus_init(struct hdac_bus *bus, struct device *dev)
> +void sof_hda_bus_init(struct hda_bus *bus, struct pci_dev *pdev,
> 
> - * snd_hdac_ext_bus_init - initialize a HD-audio extended bus
> + * snd_hda_ext_bus_init - initialize a HD-audio extended bus

Reason for renaming snd_hdac_ext_bus_init() to snd_hda_ext_bus_init() is 
argument type change: 'struct hdac_bus *' to struct hda_bus *'. Don't 
believe that's confusing to anybody.

No problem with reverting naming change for now - we can streamline 
naming later.

In regard to sof_hda_bus_init(): I don't see any renaming here, just 
argument type changes to match new snd_hda_ext_bus_init() usage.

> hda_bus is a definition from hda_codec.h, I don't see a reason why we
> should use this structure when the vast majority of the code uses
> hdac_bus. And the purpose of hdac_ext is really to deal with
> *controller* extensions to couple/decouple DMAs. There is no dependency
> on codecs at that level.

hda_bus is the base for all HDAudio drivers:
struct azx
struct skl_dev
struct sof_intel_hda_dev

So no, what vast majority of code actually does is hda_bus/codec to 
hdac_bus/codec (and vice-versa) translation when in fact all the drivers 
are hda_* based. If you speak of confusion, that's the confusion that 
should be addressed in the future..

> Even if there was, I also don't really see why/when we should start
> using hda_ext v. hdac_ext, the naming convention completely escapes me.
> It would seem logical to me to only use hdac_ext as an extension of
> hdac_, no?
> 
> I also don't get what this means:
> +	snd_hda_ext_bus_init(hbus, pci, NULL, ext_ops, "sklbus");
> 
> what is 'sklbus' and what purpose are you trying to accomplish with this
> change?
> 

Well, please see the updated declaration of snd_hda_ext_bus_init() in 
this very patch and then the existing code of 
sound/soc/intel/skylake/skl.c - skl_create().
Last argument in updated declaration reads 'modelname'. Skylake-driver 
has its own, SOF initializes it differently.


Regads,
Czarek