Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753306Ab0KWMnF (ORCPT ); Tue, 23 Nov 2010 07:43:05 -0500 Received: from comal.ext.ti.com ([198.47.26.152]:34383 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750952Ab0KWMnD convert rfc822-to-8bit (ORCPT ); Tue, 23 Nov 2010 07:43:03 -0500 From: "Nori, Sekhar" To: Ben Gardiner CC: Kevin Hilman , "davinci-linux-open-source@linux.davincidsp.com" , "linux-input@vger.kernel.org" , Dmitry Torokhov , "Govindarajan, Sriramakrishnan" , Paul Mundt , "linux-kernel@vger.kernel.org" , Alexander Clouter , Chris Cordahi Date: Tue, 23 Nov 2010 18:12:38 +0530 Subject: RE: [PATCH v2 4/4] da850-evm: add baseboard UI expander buttons, switches and LEDs Thread-Topic: [PATCH v2 4/4] da850-evm: add baseboard UI expander buttons, switches and LEDs Thread-Index: AcuKT8UFis+zfA4jTgerB3Hb5DuSqwAu6W3Q Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1739 Lines: 42 Hi Ben, On Mon, Nov 22, 2010 at 19:45:46, Ben Gardiner wrote: > Hi Sekhar, > > On Mon, Nov 22, 2010 at 7:00 AM, Nori, Sekhar wrote: > > Thanks for the explanation. I should have probably asked > > earlier, why do we need to prevent sysfs access of > > deep sleep enable and sw reset pins? We don't seem to be > > using them in the kernel either. > > You're welcome. > > I was assuming that those pins were not exported as gpio pins on > purpose; I was taking the prudent approach to prevent haphazard > toggling of sw_rst and deep_sleep_en from userspace. sw_rst because it > could initiate a reset of the cpu when toggled and deep_sleep_en > because it can override the behaviour of davinci_pm_enter(). > > I'm not sure how they would be used by existing kernel classes either. > The sw_rst pin could be used for reset but since it is on the other > end of an i2c bus and there is an existing implementation of reset > using the on chip watchdog I don't think it would be benficial to > switch. Deep_sleep_en could override the behaviour in > davinci_pm_enter() -- _maybe_ (I don't really know) it could be used > as a hardware-assisted suspend-blocker? But I totally guessing here. My preference would be to leave these pins as is (don't call a gpio_request() on them) till someone comes up with a use case for them. From what you described, sysfs access cannot happen "accidently" so someone accessing these pins from sysfs surely knows what he is doing. Thanks, Sekhar -- 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/