Subject: Re: [PATCH 3/7] ALSA: add shell for Intel HDMI LPE audio driver
Why do we need a "shell" and indirect calls?
This is a small driver set, so it's not utterly unacceptable, but it still makes
things a bit more complicated than necessary, so I'd like to understand the
idea behind it.
The 'shell' comes from an early prototype which didn't do much except
create the device. The title of the commit should be changed if it threw
you off.
This solution does not use component interface to talk between
Audio and i915 driver. The reason for that is the HDMI audio device is created
by i915 driver with only one callback pointer passed as pdata. Unlike HDA, the HDMI audio
driver does not get loaded if the i915 does not create child device.
Since there is only one callback needed we are not using the component
interface to make things simpler.
This design was co-worked with i915 folks to makes interaction simpler.
The interaction between i915 and audio is simple, yes, it just exposes
a few things, mmio ptr, irq, etc. But still I don't understand why
multiple layers of indirect accesses are needed *inside* lpe audio
driver itself. For example, suspend/resume action is cascaded to yet
another ops.
I would understand if this "shell" provides a few thin accessors to
the raw i915 registers. But another layering over a single driver
implementation makes little sense in regard of abstraction. (If there
were multiple class inherits, it's a different story, of course.)
No disagreement here Takashi.
I was planning to remove this abstraction in a second incremental pass
that would only be on the audio side, for now keeping this layer would
allow me to add the DisplayPort changes faster. If we simplify this now
then I will have so many differences with the legacy code it'll be a
nightmare. I have no emotional attachment to the legacy but it's just
pragmatic to avoid changing everything at once.
As you also mentioned it, this second pass could also reuse all the ELD
parsing that is still duplicated. These HDMI patches are not a
single-shot contribution, you'll have updates coming your way.
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