Hi Jacopo, thanks for reviewing. On 15/09/20 15:34, Jacopo Mondi wrote: > 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 ? I think you're right. Incoming v2 with the new layout as you suggested. -- Luca
