From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757828Ab1GDPov (ORCPT ); Mon, 4 Jul 2011 11:44:51 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:56439 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755756Ab1GDPou (ORCPT ); Mon, 4 Jul 2011 11:44:50 -0400 Date: Mon, 4 Jul 2011 09:44:47 -0600 From: Grant Likely To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, sodaville@linutronix.de Subject: Re: [PATCH 1/2] gpio/gpio-generic: read set register for caching if available Message-ID: <20110704154447.GG29977@ponder.secretlab.ca> References: <1309159583-11339-1-git-send-email-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1309159583-11339-1-git-send-email-bigeasy@linutronix.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 27, 2011 at 09:26:22AM +0200, Sebastian Andrzej Siewior wrote: > The ->data is a shadow copy which is used during the ->set callback in > order to avoid a read of the register before write. > If ->reg_set is set then we write to this location therefore we should > cache that value. > > Signed-off-by: Sebastian Andrzej Siewior > --- > drivers/gpio/gpio-generic.c | 5 ++++- > 1 files changed, 4 insertions(+), 1 deletions(-) > > diff --git a/drivers/gpio/gpio-generic.c b/drivers/gpio/gpio-generic.c > index 231714d..9f8b5c6 100644 > --- a/drivers/gpio/gpio-generic.c > +++ b/drivers/gpio/gpio-generic.c > @@ -398,7 +398,10 @@ int __devinit bgpio_init(struct bgpio_chip *bgc, > if (ret) > return ret; > > - bgc->data = bgc->read_reg(bgc->reg_dat); > + if (bgc->reg_set) > + bgc->data = bgc->read_reg(bgc->reg_set); On most of the gpio controllers that I've seen, the 'set' register isn't something that you can actually read. I don't think this is something that can be done for all gpio controllers. g. > + else > + bgc->data = bgc->read_reg(bgc->reg_dat); > > return ret; > } > -- > 1.7.4.4 >