Re: [PATCH 1/3] ASoC: SOF: Parse fw/tplg filename from DT

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

>>>> Introduce two DT properties in dsp node:
>>>>       * fw-filename, optional property giving the firmware filename
>>>>       (if this is missing fw filename is read from board description)
>>>>       * tplg-filename, mandatory giving the topology filename.
>>>
>>> These sound entirely like operating system configuration which I'd
>>> expect to be inferred from the machine identification.  What happens if
>>> a system has multiple options for firmware files, or if the OS ships the
>>> topology and firmware bundled up in a single image to avoid them getting
>>> out of sync?  What's the benefit of putting them in the DT?
> 
> Can you help me with this, specifically for selecting topology name.
> 
> I think I'm fine selecting a default value for SOF firmware name. It
> looks like even
> for Intel platforms there is no way of changing the firmware name.
> 
> But how about selecting topology name? We have lots of audio scenarios
> that can run on the exact same hardware:
> - e.g
>    - Audio PCM playback + Post Processing
>    - Audio Compress playback
>    - Keyword detection
> 
> 
> So, we need to use different topologies to select the scenario we want
> to demonstrate.
> 
> Would it be acceptable to add tplg_name as a module parameter?

we already have a "tplg_path" module parameter which was intended to differentiate between product skews/versions using the same hardware and firmware version. A typical example would be an OEM using 'public' firmware + topology for basic audio support, distributed through sof-bin and packaged by distros, and 3rd-party/closed sources firmware modules in more advanced packages distributed separately by the OEM. In the latter case you do want the same path for firmware and topology, otherwise you'd have a risk of using a topology making references to a library not bundled in the firmware.

There was an initial ask from Curtis to have the ability to override the firmware/topology names, but they've been able to work with the path parameters - set with udev rules for specific models.

If you wanted to demonstrate 'scenarios', you could use the same approach?

Two other points to reply to Mark:

- we currently don't support 'shipping the topology and firmware bundled up in a single image to avoid them getting out of sync'. No idea how that might work.

- if the machine driver is specified in DeviceTree, then the topology used is *required* to be aligned with the machine driver. The rules are that a topology may not make references to a BE dailink exposed in the machine driver, but conversely if the topology makes a reference to a BE dailink that is not exposed in the machine driver the topology parsing will fail. It's one of the current weaknesses of topology-based solutions, we have non-configurable hardware-related things that are described in topology but should really be described in platform firmware, be it ACPI or DT, and provided to the topology.