linux-kernel - Re: [RFC PATCH 1/2] dt-bindings: tas2562: Add firmware support for tas2563

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Date:   Wed, 10 Jun 2020 09:12:15 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Mark Brown <broonie@...nel.org>
CC:     <lgirdwood@...il.com>, <perex@...ex.cz>, <tiwai@...e.com>,
        <robh@...nel.org>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [RFC PATCH 1/2] dt-bindings: tas2562: Add firmware support for
 tas2563

Mark

On 6/10/20 5:29 AM, Mark Brown wrote:
> On Tue, Jun 09, 2020 at 02:20:29PM -0500, Dan Murphy wrote:
>> On 6/9/20 1:47 PM, Mark Brown wrote:
>>> That's really not very idiomatic for how Linux does stuff and seems to
>>> pretty much guarantee issues with hotplugging controls and ordering -
>>> you'd need special userspace to start up even if it was just a really
>>> simple DSP config doing only speaker correction or something.  I'm not
>>> sure what the advantage would be - what problem is this solving over
>>> static names?
>> IMO having a static name is the problem. It is an inflexible design.
>> Besides the firmware-name property seems to be used in other drivers to
>> declare firmwares for the boards.
>> But if no one is complaining or submitting patches within the codecs to be
>> more flexible with firmware then I can just hard code the name like other
>> drivers do.
> I'm not *completely* opposed to having the ability to suggest a name in
> firmware, the big problem is making use of the DSP completely dependent
> on having a DT property or doing some non-standard dance in userspace.

Well from what I see we have 4 options.

1.  We can have a DT node like RFC'd (Need Rob's comments here)

2.  We can have a defconfig flag that hard codes the name (This will 
probably be met with some resistance if not some really bad reactions 
and I don't prefer to do it this way)

3.  We can hard code the name of the firmware in the c file.

4.  Dynamically derive a file name based on the I2C bus-address-device 
so it would be expected to be "2_4c_tas2563.bin".  Just need to figure 
out how to get the bus number.

I don't see the user space as a viable option because the codec will 
have to load and then the user space would have to request to load the 
firmware and then more mixer controls will appear.

Again only option 1 allows us to have different firmware binaries per IC 
instance and also denotes the use of the DSP.  The DSP is not programmed 
until the user space selects the program or configuration from the 
binary.  So special audio handling is very explicit in the user space.  
More then likely most standard distributions will not even use the DSP 
for this device it is more of a specialized use case for each product.