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    SubjectRe: [RFC v2] Another approach to IR
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    On Thu, 2009-12-03 at 08:00 -0200, Mauro Carvalho Chehab wrote:
    > Andy Walls wrote:
    > > On Wed, 2009-12-02 at 14:55 -0500, Jarod Wilson wrote:
    > >> On Dec 2, 2009, at 2:33 PM, Mauro Carvalho Chehab wrote:


    > > Both of those IR devices are/will be encapsulated in a v4l2_subdevice
    > > object internally. I was going to write lirc_v4l glue between the
    > > v4l2_device/v4l2_subdev_ir_ops and lirc_dev.
    > >
    > > As for the the I2C chips, I was going to go back and encapsulate those
    > > in the v4l2_subdevice object as well, so then my notional lirc_v4l could
    > > pick those up too. The I2C subsystem only allows one binding to an I2C
    > > client address/name on a bus. So without some new glue like a notional
    > > lirc_v4l, it *may* be hard to share between ir-kbd-i2c and lirc_i2c and
    > > lirc_zilog.
    >
    > Maybe you're having a bad time because you may be trying to integrate lirc
    > at the wrong place.

    These were just ideas. I haven't done *anything* yet. ;)


    > All devices at V4L tree including ir-kbd-i2c use ir-common.ko
    > (at /drivers/media/common tree) module to communicate to IR's.
    > I'm preparing some patches to extend this also to dvb-usb devices
    > (that uses a close enough infrastructure).
    >
    > Also, most of the decoding code are there, in a form of helper routines.
    >
    > As the idea is to provide lirc interface to all devices that can work with
    > raw pulse/space, the proper place is to write a subroutine there that, once
    > called, will make those pulse/space raw codes available to lirc and will
    > call the needed decoders to export them also to evdev.
    >
    > The code at ir-common module was originally built to be used by V4L, but I'm
    > porting the code there to be generic enough to be a library that can be used
    > by other drivers. So, lirc_zilog and other lirc devices that will need to open
    > evdev interfaces after running a decoder can use them.

    I think I see what you are saying (I wish could see look at a whiteboard
    somewhere...). Wherever we come through internally to split to 2
    different userspace interfaces is fine, if you've got a big picture plan
    you think is feasible.

    That seems like a bit of perturbation to lirc_zilog and lirc_i2c. My
    thought was that lirc_v4l using the standardized v4l2_subdev_ir_ops
    interface, and maybe some new calls associted with v4l2_device, could
    subsume/unify all the functionality of lirc_i2c, lirc_zilog, ...
    lirc_whatever.

    Maybe that's just a poorly thought out dream though...


    > Due to that, we shouldn't add v4l2_subdevice there. Nothing prevents to create
    > a v4l2-ir-subdev glue if you want to see the IR's as subdevices, but this should
    > be implemented as a separate module.

    The v4l_subdevice just abstracted the IR hardware into a nice (mental)
    box for me -- easier to keep hardware separate from software decoders
    and userspace interface logic.

    Also, since v4l2_subdevices may have per subdevice /dev nodes and
    the /dev/../mcN nodes providing a discovery mechanism due to the Meda
    Controller framework, wrapping things in v4l2_subdevice may be handy for
    development and debug. Or ... as an additional operational interface to
    userspace. :D *ducks and runs for cover*

    Regards,
    Andy

    > Cheers,
    > Mauro.




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