Re: [RFC PATCH] thinkpad-acpi: Improve hardware volume controls

On Thu, May 12, 2011 at 11:39 AM, Dmitry Torokhov
[off-list ref] wrote:

Hi Andrew,

On Thu, May 12, 2011 at 10:50:54AM -0400, Andrew Lutomirski wrote:

quoted

I do, however, have a question for the input people.  Dmitry: Lenovo
makes laptops which are kind enough to tell us that the volume changed
by sending a keystroke over the atkbd-based keyboard.  (wtf!)  I've
modified the thinkpad-acpi driver to register an input handler to
catch those events coming from the keyboard and send them to ALSA
where they belong.  But if there's a keyboard grab, it won't work.
Would you accept a patch to the input layer to allow filters (or maybe
just filters that specifically request it) to run even if there's a
grab?

There is a filter on i8042 level that was introduced specifically for
cases when events not having any relation to the input are routed via
KBC interface. It looks like this is the one you want to use. See
include/linux/i8042.h::i8042_install_filter(). It allows for such events
to completely bypass input layer.

Hope this helps.

Sort of.

dell-laptop and msi-laptop are content to take some action on the keys
they see but still leave the keys in the input stream, so their job is
a bit easier.

I need to swallow one kind of extended key, detect and not swallow two
others, and ignore all the ones that are normal keys.  But that means
that I don't know whether I should filter out 0xe0 until it's too
late.

So either I'd need a function to feed an event back into i8042 or I
need to filter a little farther downstream when the keys are resolved
into keycodes (or scancodes -- I'm not really up on the terminology).

--andy