[alsa-devel] [PATCH 1/2] powerpc: add platform registration for ALSA SoC drivers

Timur Tabi timur at freescale.com
Wed Apr 28 19:27:13 CEST 2010

Grant Likely wrote:

> Didn't you just finish saying that you cannot see any situation where
> you would want the SSI devices linked into a single audio device?  So
> then if both SSIs are being used for audio, then do you not need a
> machine driver for each ssi?

That's right.  But in order for my fabric/machine driver to be called at all, I thought I needed to make it a platform driver and use platform_device_register_simple() and platform_driver_register().

>> Are you saying that I should call platform_device_register_simple()
>> from the SSI's driver initialization function, fsl_ssi_init()?
> No, I'm saying call it from the probe hook.

But then platform_device_register_simple() will be called twice, and it should be called only once. 

I must be missing something here.

> However, you should probably do a two stage platform_device_alloc() /
> platform_device_add() so you can add data (node pointer) to the
> platform device before it gets probed by the machine driver.

Don't you mean platform_device_add_resources() instead of platform_device_add()?  That is, use platform_device_add_resources() too add information about each SSI that gets probed, and then after all of the SSIs are probed, then call platform_device_add().

If that's what you mean, then where do I call platform_device_add()?

> I'm not talking about platform_data or about the ssi driver decoding
> things that the machine driver needs.  I'm talking about giving the
> machine driver a pointer to the ssi device tree node so you don't need
> to go through weird gymnastics to find the correct node again.

The only gymnastics I need to go through is this:

while ((np = of_find_compatible_node(np, NULL, "fsl,mpc8610-ssi"))) {

This finds every SSI node.  I then extract the information from the SSI nodes and all the other nodes, and then register it with ASoC. 

Timur Tabi
Linux kernel developer at Freescale

More information about the Alsa-devel mailing list