On 2019/6/1 上午5:20, Takashi Iwai wrote:
On Fri, 31 May 2019 22:59:17 +0200, Pierre-Louis Bossart wrote:
we need everything that was removed in your proposal :-)
- memset(bus, 0, sizeof(*bus));
- bus->dev = dev;
- bus->io_ops = &io_ops;
- INIT_LIST_HEAD(&bus->stream_list);
- bus->irq = -1;
- bus->ext_ops = ext_ops;
- /*
* There is only one HDA bus atm. keep the index as 0.* Need to fix when there are more than one HDA bus.*/- bus->idx = 0;
- spin_lock_init(&bus->reg_lock);
This is the smallest set of initialization needed when you don't need hdmi/hdaudio codec support.
I don't understand it... Why SOF core needs to initialize the content of HD-audio bus object even if you won't use it?
we do use it left and right, but we only use the 'controller/DMA' parts of that structure. we have zero use for CORB/RIRB and codec-specific stuff when I2S and DMIC are the only connections to 3rd party chips
So you want to avoid the dependency on snd-hda-core if the system is with only I2S/DMIC?
Hi Takashi, yes, that's true. We want to reuse the hdac registers access part(bus->io_ops, bus->stream_list), for host DMA stream management(e.g. in sof/intel/hda-stream.c), without the dependency on snd-hda-core.
But, snd-sof-intel-hda-common already has the hard dependency on snd-hda-core if CONFIG_SND_SOC_SOF_HDA is enabled. So the attempt makes little sense as long as CONFIG_SND_SOC_SOF_HDA is set.
And, if CONFIG_SND_SOC_SOF_HDA isn't set -- i.e. CONFIG_SND_SOC_HF_HDA_LINK isn't set either; it implies that there can be no user of HD-audio bus. So, I see no big reason we need to care about the stuff...
IOW, what's the merit of having hda-bus.c with the copy of snd-hda-core code? As far as I see, both hda.c and hda-bus.c are linked into the same snd-sof-intel-hda-common module. And, the former has the direct calls of HD-audio core API (with CONFIG_SND_SOC_SOF_HDA); i.e. snd-sof-intel-hda-common already depends on snd-hda-core if CONFIG_SND_SOC_SOF_HDA is on, no matter how you code hda-bus.c.
I agree we could implement hda-bus in a cleaner way - but it's a very small file.
Yes, but this is a kind of layer violation. Imagine you do initialize the struct pci_dev or whatever else device object because you want to reduce the dependency on other core helpers; it would be nightmare from the maintenance POV.
I've had already hard time to figure out why SOF HDA initializes the HD-audio bus, because it misses the explicit snd_hdac_*_bus_init() call. That's the starting point of this thread.
So, let's avoid ugly hacks. Make it more straightforward. Again, if the module size matters, we can split and reduce the part of HD-audio core stuff that is directly linked to SOF core.
If we can split HD-audio core stuff to provide a host DMA/stream only module for I2S/DMIC, that would be great.
Thanks, ~Keyon
A larger core repartitioning would take quite a bit of time, and in the mean time we already have to sort out all the deltas between legacy driver and hdac library.
Anyways, that's it for me this week, enjoy your vacation!
Thanks!
Takashi