Re: [PATCH] input: evdev: Add a read() callback

Mark:

On Mon, Feb 21, 2011 at 10:33 PM, Mark Brown
[off-list ref] wrote:

But surely the most obvious solution here is to standardise a rate
control interface?

Yes, and no.  A standardized rate control interface would deal with
the rate control problem, but leave the synchronization problem
unsolved.

The problem you're trying to solve is also an issue for really common
and standard things like touchscreens and polled switches/keys (the
latter of which you mentioned in your mail) which are used by standard
applications.

The existing "polled switch" implementation sets up a throttled
polling loop in kernel code.  The "polled switch" that I was thinking
of when I wrote the essay for the commit was "a switch that is polled
each time read() gets called".  I should have been clearer--- and
probably picked a different name.  :)

Have you looked at the IIO subsystem for things like this?  There has
been talk of putting accelerometers in there and it certainly fits in
with the sync requirements you're mentioning.

Now that I have found the code, I'm looking at it.  Can't say yet
whether it's the solution I'm seeking, or not.

The problem with your proposal as it stands is that if they do use the
new interface they interact badly with existing applications.  This
isn't really a decision the driver should be taking, it needs to be
userspace policy if it's going to be a decision at all.

Yea, I'm agreeing with you more than I was at the beginning of this thread.


b.g.
-- 
Bill Gatliff
bgat@billgatliff.com
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