On Tue, Mar 04, 2008 at 06:55:49PM +0000, Peter Stokes wrote:

On Tuesday 04 March 2008 12:47:15 Ville Syrjälä wrote:

quoted

On Sat, Feb 16, 2008 at 04:22:43PM +0000, Peter Stokes wrote:

quoted

The attached patch reconfigures the ati_remote2 driver to use
soft-autorepeat functionality and adds support for loadable key maps.

Why was this submitted (and even accepted) without cc:ing me?

I am very sorry, that was my fault, I should have cc'd you on the original 
mail.

Apology accepted. No harm done :)

quoted

quoted

I have reconfigure the driver to use the input system's built-in
autorepeat functionality as the device only appears to be able to produce
key repeat notifications at a fixed period. Switching to the software
autorepeat functionality provides more precise configuration of the
timings requested for repeat-delay and repeat-rate.

The soft-autorepeat support should be split into a separate patch. I don't
need such fast repeat but if it helps people I'm fine with it.

My reasoning behind modifying the ati_remote2 driver to use the  
soft-autorepeat implementation provided by the core input system was based 
upon the following:

* It states, in section 1.8 of "Documentation/input/input-programming.txt", 
the following:

  1.8 Key autorepeat
  ~~~~~~~~~~~~~~~~~~

  ... is simple. It is handled by the input.c module. Hardware autorepeat is
  not used, because it's not present in many devices and even where it is
  present, it is broken sometimes (at keyboards: Toshiba notebooks). To enable
  autorepeat for your device, just set EV_REP in dev->evbit. All will be
  handled by the input system.

* Using soft-autorepeat provides a more accurate behavior (the initial delay 
and the repeat rate behave as configured, as opposed to being rounded up to 
the nearest multiple of the hardware's, apparently fixed, repeat 
notifications (the hardware based repeat behavior also introduces timing 
aliasing where the actual interval between successive repeats is 
inconsistent).

* Using soft-autorepeat makes the code in ati_remote2 slightly simpler.

Right. I think the only downside is additional timer interrupts to
handle the soft repeat. Probably the effect is too minimal to even
consider.

Dmitry did suggest using soft-repeat when I originally submitted the
driver but I had no need for a faster repeat rate so I didn't change the
driver to use it.

I am happy to produce a separate patch containing only the changes necessary 
to switch the ati_remote2 driver over to use the soft-autorepeat behavior, if 
that is indeed the consensus regarding the best approach to take.

Yes, I'd like one patch per feature.

As for ensuring that the mouse buttons on this device do not have auto-repeat 
behavior applied to them. I was very unsure of my proposed solution, as I 
attempted to express in my initial email on the subject. It does however 
strike me that if mouse buttons (and perhaps other button/key codes) should 
not be auto-repeated then these codes should be excluded from the auto-repeat 
implementation within the input core. Experimentation using my Microsoft 
Internet Keyboard appeared to indicate that regular keys where repeated but 
the extra buttons (things like launch email, launch web browser etc.) are not 
(my investigations appeared to indicate, contrary to section 1.8 of the 
documentation quoted above, that the repeat behavior was being performed by 
the hardware and not by the input system's soft-autorepeat implementation). 
This behavior appears to approximately coincide with the boundary described 
by the KEY_MIN_INTERESTING define but I had no idea whether that was merely 
coincidence.

I am happy to implement multiple input devices, one for the mouse, and one for 
the keyboard. If my understanding is correct, this would break backwards 
compatibility as the two devices would be exposed by the evdev driver as two 
separate event devices?

If anyone can suggest the best approach to this problem I would be happy to 
develop the necessary patches to implement the chosen solution.

Ah, the backwards compatibility angle. It would be rude of us to break
the behaviour like that. It probably wouldn't affect my typical use case
(MPlayer + DirectFB) since I typically only use the keyboard part of the
remote. But if there are people using both "components" of the remote they
would have to change their configuration or in the worst case their code to
handle such a change. Not nice at all.

quoted

quoted

As this device is exposed as a combined keyboard and mouse, this change
somewhat depends upon the suggested modification to the core
soft-autorepeat functionality as outlined in my previous post to the
linux-input mailing list (on 12th Feb 2008 entitled "Soft-autorepeat
functionality"), without that modification, the mouse buttons are
autorepeated :-(

The loadable keymap support exposes the ability to map 5 separate
keycodes to each key (depending on which "mode" the remote control is
currently in). Additionally, I have attempted to ensure that the
scancodes used to map keycodes to the keys lie outside of the range
normally covered by regular keyboards so as to avoid requests to remap
the keys on the remote from being intercepted by a normal keyboard.

I thought the idea of input devices was to reflect the hardware and the
keymaps should be handled in userspace. If that's not the case then I think
the keymap support code should not be inside the driver but instead inside
the input core. We don't want such invasive changes in every driver do
we?

If I may explain my reasoning behind proposing the changes associated with the 
loadable keymap support. I would welcome any feedback on my reasoning and 
approach.

My initial problem was that some of the keycodes mapped in the ati_remote2 
driver have values greater than 255 and as such I am unable to obtain the 
input from pressing those keys in X windows (perhaps I'm missing some 
required configuration of X windows somewhere?). Upon further investigation 
into this I noticed that the input core provides a mechanism for altering the 
keymap configuration but the ati_remote2 driver is not compatible with it.

Ah, the dreaded X angle :) A bit of googling tells me that the X guys
don't have a real fix coming any time soon. I suppose that is one reason
for having some kind of keymap support in the input core. I personally
don't care for it but there are apprently too few people who can digest
the Xorg code so I suppose it has a compelling reason for existence.

Initially I simply modified the ati_remote2 to use the mechanism provided by 
the input core. Having done that, it occurred to me that the mode buttons of 
of the remote could be employed to effectively provide five sets of key 
mappings and I thought that this might be of some use to someone somewhere...

I appreciate that the implementation I have suggested is probably not in line 
with the original intended functionality of the loadable keymap support in 
the input system. But it does get round my issue with X windows....

It also occurred to me that perhaps the multiple-keyboards should be exposed 
as separate input devices, but again, if my understanding is correct, that 
would break backwards compatibility.

Any suggestions on better approaches would certainly be greatfully relieved.

I think you could implement the multiple keymaps thing rather trivially
in user space by having a small daemon listening on the event device and
loading a new keymap when a mode key is pressed. That would limit the
changes to the driver, and it would not require any kernel changes when
if you would need to adapt it to a device that uses a different driver.

I think the only problem is the grab thingy. I'm not sure if the Xorg 
evdev driver grabs the device, but if it does then the daemon wouldn't
be able to see the events. DirectFB's input driver does grab the device 
to prevent events leaking to the console (ctrl-c combination was
rather unpleasant without the grab). One solution would be a more
light weight grab that would only prevent the console from receiving the
events but would let other applications to see them. I remeber seeing
some discussion around device grab in the past. I wonder if anything
useful came of it...

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html