Updating a codec?
 

I need to update a codec for an old kernel; specifically, updating the WM8753 to the WM8750 on kernel-2.6.35.14. The CODEC itself exists in the kernel. Other than adding the new codec into the .config file s/t:

CONFIG_SND_SOC_IMX_CCWMX51_WM8750=y
and
CONFIG_SND_SOC_WM8750=y

what does it take?

The documentation found in the kernel/documentation/sound/alsa/soc directory mentions a: codec, platform and machine driver. However, a simple grep search for "wm8753" reveals that there is more than just 3 .c files referencing the codec. Granted, many of these files will be for different boards mine is an imx51 so I can eliminate most of them. I believe I have found the machine driver: sound/soc/imx/imx-ccwmx51-wm8753.c the rest of the files referencing "wm8753" are located @ arch/arm/mach-mx5 and so I am assuming these are the platform drivers?

What I was hoping was that I could simply change any reference of the wm8753 to wm8750 but most of my experience with hardware was in college on DOS systems using programs like Quartus and languages like VHDL. Actually writing drivers is something I have never done before and I am new to the Linux world as well.

That being said if anyone has any experience with this sort of thing I am all ears and I would be interested to know what you have to say or any advice you might be able to give me!

Where is the new module coming from? Do you simply want to reconfigure the kernel? Do you have the kernel sources installed? This might help, depending on what exactly you're trying to accomplish. https://kerneltweaks.wordpress.com/2...l-source-code/

If you just want to reconfigure the existing kernel to include different parts, switch to the kernel source directory and run 'make menuconfig' as root.

This is how I went about getting the new codec to show up in the .config file in the main kernel directory. What I am attempting to do now is make all the necessary changes in the drivers so that this codec can be used.

Maybe I should have mentioned. There was an update in the actual physical codec on the board, along with a new amplifier. I am attempting to get that new hardware working.

EDIT: Essentially, I believe what this boils down to is being able to adapt the old machine driver for the wm8753 to work with the wm8750 but there is no documentation on how to right machine drivers for specific codecs that i can find. So if anyone has ever written a machine driver for a codec then feel free to comment.

Here is the error I am receiving when I boot the kernel:

Unknown hardware: "WM8750" "" "" "" ""
Hardware is initialized using a guess method
alsactl: set_control:1255: failed to obtain info for control #2 (No such file or directory)
alsactl: set_control:1255: failed to obtain info for control #6 (No such file or directory)
alsactl: set_control:1255: failed to obtain info for control #7 (No such file or directory)
alsactl: set_control:1255: failed to obtain info for control #8 (No such file or directory)...

Anyone have an idea of how I am supposed to initialize this hardware? I figure that is the machine drivers job but I think I have that built correctly so maybe not?

Does it boot all the way? Or does that error stop the process? Maybe the module isn't loading.

It does boot all the way. I am under the assumption that it may not actually be loading in my edited version of the kernel:

I will try booting again with a versioned kernel.

After versioning my kernel I could tell it was actually using my altered kernel. So I feel like my machine driver is correct and should work. However, I am getting an error in the boot process:

Unknown hardware: "WM8750" "" "" "" ""
Hardware is initialized using a guess method
alsactl: set_control:1255: failed to obtain info for control #2 (No such file or directory)
alsactl: set_control:1255: failed to obtain info for control #6 (No such file or directory)
alsactl: set_control:1255: failed to obtain info for control #7 (No such file or directory)

I have looked online and have gotten mixed information on how to deal with this error. It was sugjested that I turn off debugging in alsa config:

│ │ [ ] Verbose procfs contents │ │
│ │ [ ] Verbose printk │ │
│ │ [ ] Debug │ │
│ │ [ ] Generic sound devices --->

I did that. It was also suggested that I look for and delete a .state file but my system does not seem to have any .state files in it.

Still failing to get this working. Some of my debugging output:

So it would seem my card is registering correctly. However, if I plug in one of the devices with the older codec I get:

I am not sure what the significance of missing the "HiFi-0" is.

If I run this same command with an older codec (working hardware) I get the same error:

I am lost :(

maybe you need to re-evaluate your original assumption:
why do you need an old kernel?
why do you need a new codec?

The old kernel was customized by Digi for their SOM which was built on top of the i.MX51 board. The old codec is no longer being produced (EOL) so the new codec is replacing that hardware.

An update:

I have managed to get the error to change (somewhat). I changed the naming convention in the mach-mx5 directory and the sound/soc/imx directory. Now instead of saying:

it simply says:

Here is some extra info: