From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rafi Rubin Subject: Re: [PATCH] input: mt: introduce MT event slots Date: Thu, 08 Apr 2010 17:23:53 -0400 Message-ID: <4BBE4969.60802@seas.upenn.edu> References: <1270685590-2204-1-git-send-email-rydberg@euromail.se> <87tyrmiqw2.fsf@troilus.org> <4BBDA555.1020003@euromail.se> <4BBE2B4D.9040808@seas.upenn.edu> <4BBE3BC4.2030503@euromail.se> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4BBE3BC4.2030503@euromail.se> Sender: linux-kernel-owner@vger.kernel.org To: Henrik Rydberg Cc: Michael Poole , Dmitry Torokhov , Andrew Morton , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-input@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 04/08/10 16:25, Henrik Rydberg wrote: > Rafi Rubin wrote: >> On 04/08/2010 05:43 AM, Henrik Rydberg wrote: >>> Michael Poole wrote: >>> [...] >>>> >>>> How would the slot number for a contact be chosen? >>> >>> The device driver determines how to use the slots. The driver calls >>> input_mt_slot(dev, slot), sends the data for the slot, picks another >>> slot, and >>> repeats. >>> >> >> Is there any particular downside to defaulting to implicit slot ids? > > Yes. The device driver should not have to update every slot between > synchronizations, or the point would be lost. > >> For drivers/hardware that don't handle tracking, SYN_MT_REPORT could >> just result in dev->slot++ and a SYN_REPORT resets dev->slot to 0; > > Drivers that do not handle tracking should not use the slots at all. The slot > concept requires that whatever gets communicated over it is identifiable, or > else it would not be possible to send changes. Drivers without tracking > capabilities should stick to the current MT protocol, for which it was designed. That's unfortunate. I think tracking upsets are generally quite rare (at least for the n-trig hardware), and we would see most of the benefit of jitter and bandwidth reduction even if we use contact ordering for slots. Tracking upsets would still flow downstream, a large state change should cause the slot to emit the new position. I was also hoping the slotting mechanism might be a good place to inject generic tracking support later. Rafi -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAku+SWcACgkQwuRiAT9o60894wCg1lQIzcFgmUNqUpiKJSDigxNE QVcAn3YylXnlNaieGTJyQ2UblpqR5X7q =EokA -----END PGP SIGNATURE-----