Ethin,

In terms of defining the protocol stack it is good to start with the producers and consumers and think about the problem from both perspectives. It is easy enough to think about the producer part of it as you are thinking about writing the driver. The driver is going to consume things like the PCI I/O Protocol. 

The consumer of the sound Protocol is going to most likely be generic EFI platform code, and possibly an OS loader. In the boot process Audio has traditionally be used for error codes, sign of life (for example the famous Mac startup sound). We are also would like to have the option of enabling better accessibility features, especially for people how are visually impaired. These days a lot of software engineers think of disk space as free and really don’t consider the size of software, but this is not true for firmware. Firmware generally lives in NOR FLASH that is considered expensive (it is more expensive than NAND, but at the same time more reliable) so firmware implementations are constrained by the size of the code that can be carried, and the size of assets/resources that can be used for user interfaces. The OS loader is some what less constrained, but it still has to share the EFI System Partition on the disk with potentially other OS loaders. 

So the consumer wants a protocol that is unleveled and focused on the task at hand. I’m not too caught up on the names but in general I think things you want are (How many knobs we need is probably better answered by an audiophile, and that is not me):
1) CompatibleBuffer() - Does driver support this buffer format. 
2) PlayBuffer() - Play the sound
a) We probably want a synchronous and asynchronous version of this API. For example you don’t want to slow down the boot to wait for a boot beep to complete, and you may chose to implement an API that waits for the sound to complete (and do some GUI work in parallel) vs. blocking on the sound. 
b) async in EFI usually means you return a pointer to an EFI_EVENT that gets signaled on completion.  
3) StopBuffer() - In case the asynchronous PlayBuffer() needs to be stopped. Think error exit. 
3) SetVolume()/GetVolume() - Set/Get Volume in units of 0 - 100 (trying to avoid db as that gets into capability and math that is likely best abstracted by the driver)?
4) Mute()/UnMute() - Mute and volume are often independent features in a UI keeping them separate in API makes it easier to implement things. 
5) PlayTone() - Maybe for error sounds that don’t require canned sound files. Maybe TimeOn, TimeOff, Frequency, and how many times to repeat. 
6) Do we need tuning values or Tone settings? 

At some point we might consider defining nvram variable for the default state of some of the tunable, especially mute and volume. For example the user may want to turn off all volume on the system so it would be nice if the OS can set the EFI volume and mute. In the short run we can probably use PCD values to set the default values. 

So I think we have a generic AUDIO API on top and likely a PCI I/O on the bottom. If we need more protocols to manage hardware devices then those protocols can be defined in the context of that hardware. So for example we would probably end up with an HDA_CODEC protocol. I think the best way to think about this is a disk. A lot of disk adapters just produce a raw Block I/O  protocol, but for a more common bus like ATA or SCSI you might have an extra driver in place to make the common bits common code. I think some of the same layers may be in place here. So likely VirtIo is simple and just produces the generic AUDIO API, while an HDA audio driver also has to abstract some of the complexity of its hardware implementation and standard. 

In terms of picking the set of APIs and tunables it is probably good to start with VirtIo and USB and see what set make sense and what you could and could not implement. HDA Audio is so complex you might want to look at it in terms of the minute you have to implement to make it function. Think what assumptions are you forced to make to implement. 

This is a vey 10,000 foot view to start with. I think you will need to mix this in the the reality of how it works in the real world to figure out the right abstraction, but then again that is the beauty of having an implementation. Likely also get some feedback from audiophiles. 

Oh and make sure you don’t go off an implement a lot of code just because we chose the wrong complexity or abstraction point. This is the one time we get to change the public APIs so lets feel free to adjust them to make the most sense for the job at hand. 

Thanks,

Andrew Fish

On Apr 13, 2021, at 6:20 PM, Ethin Probst <harlydavidsen@gmail.com> wrote:

Okay, so looking at the EDK2 driver developers guide, here are my thoughts:

- Each audio driver will be a bus driver, even if it doesn't control
buses in the traditional sense.
- I think the initialization sequence should be different: there
should be an AudioDxe, but it should contain three separate bus
drivers for each kind of audio device supported.
- For the VirtIO audio device driver, it'll most likely consume the
PCI I/O protocol and produce the EFI_VIRTIO_AUDIO_OUTPUT_PROTOCOL and
EFI_VIRTIO_AUDIO_INPUT_PROTOCOL protocols. This will just be an
ordinary UEFI device driver.
- The HDA audio device driver will consume the PCI I/O protocol and
will produce different device handles per HDA controller found. I'd
produce a handle per codec, but that seems overkill. Each handle will
be attached to both an audio stream protocol and a controller
management protocol. The audio stream protocol will manage the
creation, control, and deletion of audio streams as well as the
processing of audio data. The controller management protocol is
responsible for allowing applications or other drivers to manage the
HDA controller itself.

I haven't planned for the USB audio device driver yet, but these are
my thoughts so far. What do you guys think? Am I over-complicating
this setup? How can it be improved upon?

On 4/13/21, Ethin Probst via groups.io
<harlydavidsen=gmail.com@groups.io> wrote:
Hi Andrew,

The developer guide for EDK2 drivers is a godsend. Thank you very
much, and thank you, Mike, for your excellent work on the guide! I may
just ahve to do my building on Linux and not Windows -- unless the Bug
-- bug 3302 -- has been fixed. I'll have to do testing on Linux, at
any rate, since Windows hosts do not support VirtIO emulation and I
can't seem to find any way of emulating them in a guest machine with
Windows as a host.

On 4/13/21, Andrew Fish <afish@apple.com> wrote:


On Apr 13, 2021, at 9:53 AM, Ethin Probst <harlydavidsen@gmail.com>
wrote:

Would it be possible for us to conduct discussion on the UEFI talkbox?
I don't mind using email, but things could definitely get moving
quicker over there (though its not a requirement obviously).


Sure, don’t think I’ve really used that but as long as I get pointed int
he
right direction I can make it work.

For a device driver the general UEFI model is for the Entry point of the
driver to publish a EFI_DRIVER_BINDING_PROTOCOL[1]. The Supported()
function
matches on the PCI devices. The Start() function installs the Protocols
to
do work, and the Stop() undoes the Start().

Mike Kinney started this back in the day and it describes how to write
UEFI
drivers:
https://github.com/tianocore/tianocore.github.io/wiki/UEFI-Driver-Writer%27s-Guide

[1]https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Protocol/DriverBinding.h#L157

Thanks,

Andrew Fish

Here's how I generally envision the driver functioning:

1. Firmware/platform code calls InitaudioOutput() or something like
it. This function scans the PCIe bus and scans for one of the
following:
- Vendor ID 0x1AF4, device ID 0x1059: VirtIO sound device
- PCI class 0x0C, subclass 0x03, program interface 0x30 or 0x40: for
USB audio interface (I'm only thinking of targeting XHCI and USB 4,
and not UHCI, OHCI or EHCI). But maybe EDK2 will take that out of my
hands. If so, it will make things easier.
- For USB audio devices I'm not quite sure what to look for; I'm
definitely unused to USB.
2. If any of the above cases are found, appropriate driver
initialization occurs. Since for the time being I am solely focusing
on VirtIO sound devices, the VirtIO general initialization sequence
will occur as outlined in sec. 3 of the VirtIO specification available
at https://www.kraxel.org/virtio/virtio-v1.1-cs01-sound-v7.html
<https://www.kraxel.org/virtio/virtio-v1.1-cs01-sound-v7.html>.
As for actual protocol exposure that would be spec-worthy, for
EFI_AUDIO_OUTPUT_PROTOCOL, I'm not quite sure what to expose. VirtIO
is rather simple: there's a buffer for sending and receiving audio
data in PCM streams. So for that we could expose a Reset(),
RemapJack(), GetJackConfig(), GetPcmConfig(), SetPcmParams(),
Prepare(), Release(), Start(), and Stop() function for the
corresponding request types VIRTIO_SND_R_JACK_GET_CONFIG,
VIRTIO_SND_R_JACK_REMAP, VIRTIO_SND_R_PCM_GET_CONFIG,
VIRTIO_SND_R_PCM_SET_PARAMS, VIRTIO_SND_R_PCM_PREPARE,
VIRTIO_SND_R_PCM_RELEASE, VIRTIO_SND_R_PCM_START, and
VIRTIO_SND_R_PCM_STOP control requests. However, for HDA things are a
lot more complex, so I'm not sure how that should work.
For VirtIO -- which is what I'll focus on for now -- everything is
described, in excellent detail, in sec. 5.14 of the above-linked
document. What are your guys's thoughts thus far and how should
everything be mapped to UEFI interfaces?

On 4/13/21, Andrew Fish <afish@apple.com <mailto:afish@apple.com>>
wrote:
Leif,

Since I have put some brain cells around this area in the past I can be
the
backup and help out too.

I’d also point out if you are having issues building or have general
questions on how things work it is fine to use the mailing list. I’ve
got
a
lot of feedback that folks read or search the mailing list looking for
answer to their questions so one person asking can help out a lot of
other
people.

Thanks,

Andrew Fish

On Apr 13, 2021, at 5:28 AM, Leif Lindholm <leif@nuviainc.com> wrote:

Hi all, especially Ethin.

Apologies for radio silence - last week I was off on holiday, and
before
that ... let's just say corporate acquisitions generate some
distractions.
Anyway, I'm back, and since I'm down as the mentor for this task, feel
free to spam me with any remaining/new questions.

/
  Leif

On Tue, Apr 6, 2021 at 4:17 PM Ethin Probst <harlydavidsen@gmail.com
<mailto:harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>>>
wrote:
I'll attach the bug for the build tools to the BZ shortly.
Laszlo, thanks for that. I don't know their email addresses though.
And yes, I was going to make it device independent, as the majority
(if not all) of UEFI protocols are.

On 4/6/21, Laszlo Ersek <lersek@redhat.com <mailto:lersek@redhat.com>
<mailto:lersek@redhat.com <mailto:lersek@redhat.com>>>
wrote:
On 03/31/21 08:41, Nate DeSimone wrote:
Another option is to put the protocol definition in MdeModulePkg and
mark it with the EDKII_ prefix. For my last “code first” UEFI spec
contribution I did this with the PPI that added up getting added.

The new audio protocol should be generic, only its implementation in
question should be virtio specific.

Please include Gerd Hoffmann (CC'd) in the protocol design, as well
as
the developers of the virtio-sound device model in QEMU.

Thanks
Laszlo





Thanks,

Nate



*From: *<devel@edk2.groups.io <mailto:devel@edk2.groups.io>
<mailto:devel@edk2.groups.io <mailto:devel@edk2.groups.io>>> on
behalf
of "Andrew Fish via groups.io <http://groups.io/> <http://groups.io/
<http://groups.io/>>"
<afish=apple.com@groups.io <mailto:afish=apple.com@groups.io>
<mailto:apple.com@groups.io <mailto:apple.com@groups.io>>>
*Reply-To: *"devel@edk2.groups.io <mailto:devel@edk2.groups.io>
<mailto:devel@edk2.groups.io <mailto:devel@edk2.groups.io>>"
<devel@edk2.groups.io <mailto:devel@edk2.groups.io>
<mailto:devel@edk2.groups.io <mailto:devel@edk2.groups.io>>>,
"afish@apple.com <mailto:afish@apple.com> <mailto:afish@apple.com
<mailto:afish@apple.com>>" <afish@apple.com <mailto:afish@apple.com>
<mailto:afish@apple.com <mailto:afish@apple.com>>>
*Date: *Tuesday, March 30, 2021 at 10:54 PM
*To: *edk2-devel-groups-io <devel@edk2.groups.io
<mailto:devel@edk2.groups.io>
<mailto:devel@edk2.groups.io <mailto:devel@edk2.groups.io>>>,
"harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>
<mailto:harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>>"
<harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>
<mailto:harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>>>
*Cc: *Rafael Rodrigues Machado <rafaelrodrigues.machado@gmail.com
<mailto:rafaelrodrigues.machado@gmail.com>
<mailto:rafaelrodrigues.machado@gmail.com
<mailto:rafaelrodrigues.machado@gmail.com>>>
*Subject: *Re: [edk2-devel] VirtIO Sound Driver (GSoC 2021)





  On Mar 30, 2021, at 5:01 PM, Ethin Probst
<harlydavidsen@gmail.com
<mailto:harlydavidsen@gmail.com>
<mailto:harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>>
  <mailto:harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>
<mailto:harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>>>>
wrote:



  I'm wondering where exactly I should add the VirtIO sound
protocol.
I
  just familiarized myself with the build system and am about to
test
it
  by building OVMF if possible, but I'm wondering where I should
  actually put the protocol and all that stuff. Maybe there's
  documentation I've missed as well.



Ethin,



For the driver I’d match the patter of OVMF [1] and use
OvmfPkg/VirtioSoundDxe/. Maybe even use one of the other drivers as
a
template.



The protocol is more of a public thing. I think eventually we would
like
to publish the protocol in the UEFI Spec (I can help with that part)
and
that would mean we put the Protocol definition in
MdePkg/Include/Protocol, but we don’t want to do that before it is
standardized as that causes compatibility issues. So this is a “code
first project” (code prototype and then contribute to the UEFI Forum
for
inclusion in the specification) so we need to follow some code first
rules that I don’t remember of the top of my head? So why not start
out
the protocol definition OvmfPkg/Include/Protocol. You can also add a
test application looks like you can just use the root [2] of OVMF
for
that. That way the project is not blocked.



We can have a conversation on the mailing list about better places
to
put stuff, and it should be easy enough to move stuff around if
everything else is working.



[1] find OvmfPkg  -iname '*Virtio*.inf'

OvmfPkg/VirtioPciDeviceDxe/VirtioPciDeviceDxe.inf

OvmfPkg/VirtioScsiDxe/VirtioScsi.inf

OvmfPkg/Library/VirtioMmioDeviceLib/VirtioMmioDeviceLib.inf

OvmfPkg/Library/VirtioLib/VirtioLib.inf

OvmfPkg/VirtioGpuDxe/VirtioGpu.inf

OvmfPkg/VirtioBlkDxe/VirtioBlk.inf

OvmfPkg/Virtio10Dxe/Virtio10.inf

OvmfPkg/VirtioNetDxe/VirtioNet.inf

OvmfPkg/VirtioRngDxe/VirtioRng.inf



[2] /Volumes/Case/edk2-github/OvmfPkg>git grep APPLICATION -- *.inf
|
grep MODULE_TYPE

EnrollDefaultKeys/EnrollDefaultKeys.inf:13:  MODULE_TYPE
  = UEFI_APPLICATION



Thanks,



Andrew Fish






  On 3/30/21, Ethin Probst via groups.io <http://groups.io/>
<http://groups.io/ <http://groups.io/>>
<http://groups.io/ <http://groups.io/> <http://groups.io/
<http://groups.io/>>>
  <harlydavidsen=gmail.com@groups.io
<mailto:harlydavidsen=gmail.com@groups.io>
<mailto:gmail.com@groups.io
<mailto:gmail.com@groups.io>>
  <mailto:harlydavidsen <mailto:harlydavidsen>=gmail.com@groups.io
<mailto:gmail.com@groups.io>
<mailto:gmail.com@groups.io <mailto:gmail.com@groups.io>>>> wrote:

      I agree. Plus, it gives me a chance to finally learn the EDK2
build
      system and how it works! I've been working on a hobby OS as a
side
      project and, though learning from other code examples from
OSes
is
      fun, I have to say that learning from the firmware code like
from
      SeaBIOS has been some of the most enlightening and
interesting
times
      thus far.
      Thanks for the link to your code, Rafael; once I get virtIO
support
      in, I can work on HDA support, though I might tackle USB
support
      second and HDA third. We'll see, but VirtIO definitely is
coming
      first.

      As I said before, I look forward to working with all of you
      wonderful
      people!

      On 3/30/21, Rafael Rodrigues Machado
      <rafaelrodrigues.machado@gmail.com
<mailto:rafaelrodrigues.machado@gmail.com>
<mailto:rafaelrodrigues.machado@gmail.com
<mailto:rafaelrodrigues.machado@gmail.com>>
      <mailto:rafaelrodrigues.machado@gmail.com
<mailto:rafaelrodrigues.machado@gmail.com>
<mailto:rafaelrodrigues.machado@gmail.com
<mailto:rafaelrodrigues.machado@gmail.com>>>>
      wrote:

          This would be amazing so people can continue my work
related
to
          accessibility at BIOS. Something desired by the blind
people
          since the
          90's
          Just for reference, this is what I have done:


https://github.com/RafaelRMachado/Msc_UefiHda_PreOs_Accessibility
<https://github.com/RafaelRMachado/Msc_UefiHda_PreOs_Accessibility>
<https://github.com/RafaelRMachado/Msc_UefiHda_PreOs_Accessibility
<https://github.com/RafaelRMachado/Msc_UefiHda_PreOs_Accessibility>>

          Thanks
          Rafael

          Em seg, 29 de mar de 2021 20:24, Ethin Probst
          <harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>
<mailto:harlydavidsen@gmail.com <mailto:harlydavidsen@gmail.com>>>
          escreveu:


              Hello everyone,

              This is the first time I've ever contributed to EDK2.
As
              part of GSoC
              2021, I have submitted a proposal to implement a UEFI
              audio output
              protocol that will utilize the VirtIO sound driver.
I've
              already
              submitted a draft proposal, and apologize if I've
done
              things out of
              order. This is my first time doing GSoC 2021, and
              contributing to EDK2
              felt like a really fun thing to do!

              I look forward to working with you guys on this and
any
              future projects!
              :-)

              --
              Signed,
              Ethin D. Probst









      --
      Signed,
      Ethin D. Probst







  --
  Signed,
  Ethin D. Probst










--
Signed,
Ethin D. Probst










--
Signed,
Ethin D. Probst







--
Signed,
Ethin D. Probst








-- 
Signed,
Ethin D. Probst