Re: [PATCH v11 04/15] media: v4l2-fwnode: add initial connector parsing support

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Hi Sakari,

On 19-11-16 01:34, Sakari Ailus wrote:
> Hi Marco,
> 
> On Mon, Sep 30, 2019 at 11:38:49AM +0200, Marco Felsch wrote:

...

Let me sum up our irc discussion about that kAPI.

Our starting point is a fwnode based subdev which has connectors in
front of there pins. Connectors are used to limit the subdev to some
device limits e.g. if the device support only PAL-Input streams and the
subdev has an buggy autodetect mechanism. In that case the connector can
be used by the subdev to set the possible TV-Norms to PAL. Currently the
tvp5150 is the only fwnode based subdev implementing connectors.

Connectors have common and connector specific properties. All current
provided connectors can be found here:
Documentation/devicetree/bindings/display/connector/ .

Parsing the properties is common to all _upcoming_ fwnode based subdevs
so this should be done within the core. So lets move on to the parsing
helper.

> > +int v4l2_fwnode_connector_alloc_parse(struct fwnode_handle *fwnode,
> > +				      struct v4l2_fwnode_connector *connector)
> > +{

This kAPI seems to fit all current use cases. The API is not responsible
to alloc the 'struct v4l2_fwnode_connector' instead it is only used to
fill this struct. The given 'struct fwnode_handle' should be the subdev
local ep-fwnode because the user already has a reference to this ep.

This helper has two use-cases:
  1) Parsing the connector properties and add the initial (1st) link.
  2) Add further n-links upon n-calls to an already parsed connector.

Going this way we need to ensure that the caller init the 'struct
v4l2_fwnode_connector' to '0' before call this helper. This can be
documented within the kAPI doc.

Regards,
  Marco



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