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    SubjectRe: [RFC] Should we create a raw input interface for IR's ? - Was: Re: [PATCH 1/3 v2] lirc core device driver infrastructure
    From
    On Tue, Dec 8, 2009 at 9:16 AM, Mauro Carvalho Chehab
    <mchehab@redhat.com> wrote:
    > Jon Smirl wrote:
    >> On Tue, Dec 8, 2009 at 8:40 AM, Mauro Carvalho Chehab
    >> <mchehab@redhat.com> wrote:
    >>> Jon Smirl wrote:
    >>>> On Tue, Dec 8, 2009 at 7:35 AM, Andy Walls <awalls@radix.net> wrote:
    >>>>> On Mon, 2009-12-07 at 20:22 -0800, Dmitry Torokhov wrote:
    >>>>>> On Mon, Dec 07, 2009 at 09:42:22PM -0500, Andy Walls wrote:
    >>>>>>> So I'll whip up an RC-6 Mode 6A decoder for cx23885-input.c before the
    >>>>>>> end of the month.
    >>>>>>>
    >>>>>>> I can setup the CX2388[58] hardware to look for both RC-5 and RC-6 with
    >>>>>>> a common set of parameters, so I may be able to set up the decoders to
    >>>>>>> handle decoding from two different remote types at once.  The HVR boards
    >>>>>>> can ship with either type of remote AFAIK.
    >>>>>>>
    >>>>>>> I wonder if I can flip the keytables on the fly or if I have to create
    >>>>>>> two different input devices?
    >>>>>>>
    >>>>>> Can you distinguish between the 2 remotes (not receivers)?
    >>>>> Yes.  RC-6 and RC-5 are different enough to distinguish between the two.
    >>>>> (Honestly I could pile on more protocols that have similar pulse time
    >>>>> periods, but that's complexity for no good reason and I don't know of a
    >>>>> vendor that bundles 3 types of remotes per TV card.)
    >>>>>
    >>>>>
    >>>>>>  Like I said,
    >>>>>> I think the preferred way is to represent every remote that can be
    >>>>>> distinguished from each other as a separate input device.
    >>>>> OK.  With RC-5, NEC, and RC-6 at least there is also an address or
    >>>>> system byte or word to distingish different remotes.  However creating
    >>>>> multiple input devices on the fly for detected remotes would be madness
    >>>>> - especially with a decoding error in the address bits.
    >>>> I agree that creating devices on the fly has problems. Another
    >>>> solution is to create one device for each map that is loaded. There
    >>>> would be a couple built-in maps for bundled remotes - each would
    >>>> create a device. Then the user could load more maps with each map
    >>>> creating a device.
    >>> No, please. We currently have already 89 different keymaps in-kernel. Creating
    >>> 89 different interfaces per IR receiver is not useful at all.
    >>>
    >>> IMO, the interfaces should be created as the keymaps are associated
    >>> to an specific IR receiver.
    >>
    >> Each IR receiver device driver would have a built-in keymap for the
    >> remote bundled with it. When you load the driver it will poke the
    >> input system and install the map. Any additional keymaps would get
    >> loaded from user space. You would load one keymap per input device.
    >>
    >> You might have 89 maps in the kernel with each map being built into
    >> the device driver for those 89 IR receivers. But you'll only own one
    >> or two of those devices so only one or two of the 89 maps will load.
    >> Building the map for the bundled receiver into the device driver is an
    >> important part of achieving "just works".
    >>
    >> I suspect we'll have a 1,000 maps defined after ten years, most of
    >> these maps will be loaded from user space. But you'll only have two or
    >> three loaded at any one time into your kernel. You need one map per
    >> input device created. These maps are tiny, less than 1KB.
    >>
    >> Having all of these maps is the price of allowing everyone to use any
    >> more that they please. If you force the use of universal remotes most
    >> of the maps can be eliminated.
    >
    > Makes sense. Yet, I would add an option at Kbuild to create a module or not
    > with the bundled IR keymaps.
    >
    > So, it should be possible to have all of them completely on userspace or
    > having them at kernelspace.

    Removing the maps for the bundled remotes from the receiver device
    drivers will break "just works". The map will be in an __init section
    of the IR device driver. When it is fed into the input system a RAM
    based structure will be created. If you really want the 1KB memory
    back, use sysfs to remove the default map. An embedded system will
    have a bundled remote so it is going to want the map. If you want to
    change the default map loading a new map will release the memory from
    the previous map.

    >
    > Cheers,
    > Mauro.
    >



    --
    Jon Smirl
    jonsmirl@gmail.com
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