Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752645Ab0FWRIE (ORCPT ); Wed, 23 Jun 2010 13:08:04 -0400 Received: from ch-smtp02.sth.basefarm.net ([80.76.149.213]:59409 "EHLO ch-smtp02.sth.basefarm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752727Ab0FWRIA (ORCPT ); Wed, 23 Jun 2010 13:08:00 -0400 Message-ID: <4C223F60.6080904@euromail.se> Date: Wed, 23 Jun 2010 19:07:44 +0200 From: Henrik Rydberg User-Agent: Thunderbird 2.0.0.24 (X11/20100411) MIME-Version: 1.0 To: Ping Cheng CC: Dmitry Torokhov , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Jiri Kosina , Ping Cheng , Benjamin Tissoires , Chase Douglas , Rafi Rubin Subject: Re: [PATCH 2/5] input: Use driver hint to compute the evdev buffer size (rev3) References: <1277291686-7153-1-git-send-email-rydberg@euromail.se> <1277291686-7153-2-git-send-email-rydberg@euromail.se> <1277291686-7153-3-git-send-email-rydberg@euromail.se> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Originating-IP: 83.248.196.134 X-Scan-Result: No virus found in message 1ORTQR-0007DX-8g. X-Scan-Signature: ch-smtp02.sth.basefarm.net 1ORTQR-0007DX-8g 3c7d626516066dc70539f9225f5418ab Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1434 Lines: 33 Hi Ping, [...] >> @@ -51,7 +52,9 @@ static DEFINE_MUTEX(evdev_table_mutex); >> >> static int evdev_compute_buffer_size(struct input_dev *dev) >> { >> - return EVDEV_MIN_BUFFER_SIZE; >> + int nev = dev->hint_events_per_packet * EVDEV_BUF_PACKETS; >> + nev = max(nev, EVDEV_MIN_BUFFER_SIZE); >> + return roundup_pow_of_two(nev); > > I think we have a backward compatibility issue here. This routine will > return 7 when nev falls to the default value > (EVDEV_MIN_BUFFER_SIZE/64). This could happen to those drivers that > don't report MT events or forget/don't feel the need to set > hint_events_per_packet since the old BUFFER_SIZE worked perfectly for > them. We need to keep the return value for those drivers as 64 so we > could allocate the same space as it was in [PATCH 1/5]. Are you perhaps confusing EVDEV_BUF_PACKETS and EVDEV_MIN_BUFFER_SIZE? The last line ensures that the value returned is a power of two (hence not 7). The second-to-last line ensures the value is at least equal to 64 (hence not 7). The default hint value for a driver that does not do anything is zero, which leads to a return value of 64, just as it is today. Thanks, Henrik -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/