[PATCH 05/14] media: add a V4L2 OF parser

[Stephen Warren]

On 10/10/2012 07:18 AM, Laurent Pinchart wrote:
> On Monday 08 October 2012 17:15:53 Guennadi Liakhovetski wrote:
...
>> But how do you get the subdev pointer? With the notifier I get it from
>> i2c_get_clientdata(client) and what do you do without it? How do you get
>> to the client?
>>
>>> And can't it get that from DT as well?
>>
>> No, I don't think there is a way to get a device pointer from a DT node.

I don't believe there's a generic API for this (although perhaps there
could be), but it can be implemented quite easily.

For example, on Tegra, the SMMU needs to flip a bit in the AHB register
space in order to enable itself. The SMMU DT node contains a phandle
that points at the AHB DT node. The SMMU driver parses the phandle and
passes the DT node pointer to the AHB driver. The AHB driver looks up
the struct device that was instantiated for that node. See
drivers/amba/tegra-ahb.c:tegra_ahb_enable_smmu(). There are a few other
cases of similar code in the kernel, although I can't remember the others!