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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 9:40 AM, Mauro Carvalho Chehab
    <mchehab@redhat.com> wrote:
    > Jon Smirl wrote:
    >> 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".
    >
    > No. This can be provided by an udev application that will load the keytable
    > when the device is connected.

    Why do you want to pull the 1KB default mapping table out of the
    device driver __init section and more it to a udev script? Now we will
    have to maintain a parallel udev script for ever receiver's device
    driver.

    The purpose of putting this table into __init is to get rid of all
    these udev scripts in the default case.

    >
    > Of course before adding it into a module, we'll need to write such app.
    >
    > This will only affects the need of IR during boot time.
    >
    >> 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.
    >
    > We can't use __init, since another device needing the keymap may be hot-plugged.

    You can handle that with __devinit


    >> 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.
    >
    > Yes, but it needs just one map, not all of them. The maps shouldn't be linked
    > into the drivers, as the same map is used by several different devices on

    Link them or #include them, it doesn't make any difference.

    > different drivers. So, the option is to allow customizing the available keymaps,
    > if CONFIG_EMBEDDED.
    >
    > Cheers,
    > Mauro.
    >



    --
    Jon Smirl
    jonsmirl@gmail.com
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