[alsa-devel] [PATCH] ASoC drivers for the Freescale MPC8610 SoC

[Grant Likely]

On 1/2/08, Jon Smirl <jonsmirl at gmail.com> wrote:
> On 1/2/08, Grant Likely <grant.likely at secretlab.ca> wrote:
> > On 1/2/08, Jon Smirl <jonsmirl at gmail.com> wrote:
> > > On 1/2/08, Timur Tabi <timur at freescale.com> wrote:
> > > mpc8610_hpcd is the harder one to load since it doesn't have a device
> > > tree entry. What you want to do it match on the compatible field of
> > > the root node.
> > >
> > > static struct of_device_id fabric_of_match[] = {
> > >         {
> > >                 .compatible     = "fsl,MPC8610HPCD",
> > >         },
> > >         {},
> > > };
> > >
> > > But this doesn't work since the root is the device tree isn't passed
> > > down into the device probe code. (Could this be fixed?)
> >
> > The driver can always get the root node.  But better yet, instantiate
> > the correct fabric device (probably as a platform_device) from the
> > platform code.  Then the correct fabric driver can probe against it.
>
> The meaning of this has finally sunk into my consciousness. The
> platform code can create a device that isn't bound to a driver. So why
> not make this an of_platform_device?  This is basically a pseudo
> device that isn't in the device tree.

Simply because it doesn't have a device node.  That's the prime
characteristc that differentiates platform_bus from of_platform_bus.
What do you bind against in of_platform_bus if you don't have a
specific node for it?

> Alternatively, the best place for this device would be on the ASOC
> bus, but the ASOC bus hasn't been created when the platform code runs.
> Maybe I can figure out a place in the platform code to create this
> device after the ASOC driver has loaded and created the bus. Does the
> platform code get control back after loading all of the device
> drivers?

Yes, but it requires the core ASoC code to not be a module.  Then you
can use machine_device_initcall() to register the device at a later
time.

Cheers,
g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
grant.likely at secretlab.ca
(403) 399-0195