linux-kernel - Re: [PATCH 02/19] Input: Improve the events-per-packet estimate

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Message-ID: <2226930.JeU38gc4Sp@dtor-d630.eng.vmware.com>
Date:	Tue, 14 Aug 2012 12:53:56 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Ping Cheng <pinglinux@...il.com>
Cc:	Henrik Rydberg <rydberg@...omail.se>,
	Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/19] Input: Improve the events-per-packet estimate

On Tuesday, August 14, 2012 12:32:21 PM Ping Cheng wrote:
> On Sun, Aug 12, 2012 at 2:42 PM, Henrik Rydberg <rydberg@...omail.se> wrote:
> > Many MT devices send a number of keys along with the mt information.
> > This patch makes sure that there is room for them in the packet
> > buffer.
> > 
> > Signed-off-by: Henrik Rydberg <rydberg@...omail.se>
> > ---
> > 
> >  drivers/input/input.c | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/input/input.c b/drivers/input/input.c
> > index 6e90705..8ebf116 100644
> > --- a/drivers/input/input.c
> > +++ b/drivers/input/input.c
> > @@ -1777,6 +1777,9 @@ static unsigned int
> > input_estimate_events_per_packet(struct input_dev *dev)> 
> >                 if (test_bit(i, dev->relbit))
> >                 
> >                         events++;
> > 
> > +       /* Make room for KEY and MSC events */
> > +       events += 7;
> 
> Hi Henrik,
> 
> It is nice to get rid of the redundant pieces and to incorporate
> common functions. Thank you.
> 
> I have a question about the code above though.  Why do we use 7
> instead of going through the keys like:
> 
> 	for (i = 0; i < KEY_MAX; i++)
> 		if (test_bit(i, dev->keybit))
> 			events++;

Because that would result in gross over-estimation for many devices - 
my keyboard has 100+ keys but it never sends all of them in one event
frame, not even if I can get a cat to lay on it ;)

-- 
Dmitry

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