Hi Luca, On Fri, Sep 04, 2020 at 11:51:41PM +0200, Luca Ceresoli wrote: > This paragraph provides generic information to explain what v4l2_subdev is > useful for. Placing it in the middle of paragraphs describing the details > of subdev registration does not make much sense. Move it near the beginning > of the section when the v4l2_subdev idea has just been introduced and > before going into its details. > > Signed-off-by: Luca Ceresoli <luca@xxxxxxxxxxxxxxxx> > --- > Documentation/driver-api/media/v4l2-subdev.rst | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst > index fb66163deb38..1c1e3f9da142 100644 > --- a/Documentation/driver-api/media/v4l2-subdev.rst > +++ b/Documentation/driver-api/media/v4l2-subdev.rst > @@ -12,6 +12,12 @@ Usually these are I2C devices, but not necessarily. In order to provide the > driver with a consistent interface to these sub-devices the > :c:type:`v4l2_subdev` struct (v4l2-subdev.h) was created. > > +The advantage of using :c:type:`v4l2_subdev` is that it is a generic struct and > +does not contain any knowledge about the underlying hardware. So a driver might > +contain several subdevs that use an I2C bus, but also a subdev that is > +controlled through GPIO pins. This distinction is only relevant when setting > +up the device, but once the subdev is registered it is completely transparent. > + > Each sub-device driver must have a :c:type:`v4l2_subdev` struct. This struct > can be stand-alone for simple sub-devices or it might be embedded in a larger > struct if more state information needs to be stored. Usually there is a > @@ -235,12 +241,6 @@ it can call ``v4l2_subdev_notify(sd, notification, arg)``. This macro checks > whether there is a ``notify()`` callback defined and returns ``-ENODEV`` if not. > Otherwise the result of the ``notify()`` call is returned. > > -The advantage of using :c:type:`v4l2_subdev` is that it is a generic struct and > -does not contain any knowledge about the underlying hardware. So a driver might > -contain several subdevs that use an I2C bus, but also a subdev that is > -controlled through GPIO pins. This distinction is only relevant when setting > -up the device, but once the subdev is registered it is completely transparent. > - Have you considered moving the whole part that describes how to call operations, which comes after the synchronous registration case to a dedicated sub-section ? The above paragraph makes sense in the context of describing why v4l2_subdev is advantageous as it abstract the underlying details under a unified call interface. This could become V4L2 sub-devices ---------------- Intro ~~~~~ Registration ~~~~~~~~~~~~ **synchronous** **asynchronous** Operations call (or a better name :) ~~~~~~~~~~~~~~~ What do you think ? Thanks j > In the **asynchronous** case subdevice probing can be invoked independently of > the bridge driver availability. The subdevice driver then has to verify whether > all the requirements for a successful probing are satisfied. This can include a > -- > 2.28.0 >
