From: "Henrik Rydberg" <rydberg@euromail.se>
Date: Tue, 14 Aug 2012 22:01:53 +0200
To: Ping Cheng <pinglinux@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>, Jiri Kosina <jkosina@suse.cz>,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 02/19] Input: Improve the events-per-packet estimate
Message-ID: <20120814200153.GA3525@polaris.bitmath.org>
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Hi Ping,

Long time no see. :-)

> > +       /* Make room for KEY and MSC events */
> > +       events += 7;
> 
> 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++;

Keyboards register a large amount of different keys, but seldom send
more than one or two at a time. The value 7 is ad hoc, admittedly, but
it makes the default buffer 8 bytes, which happens to precisely match
the default buffer in evdev.

Thanks,
Henrik
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