From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]:41110 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935536Ab3DPRgg (ORCPT ); Tue, 16 Apr 2013 13:36:36 -0400 Message-ID: <516D8C1E.2080704@redhat.com> Date: Tue, 16 Apr 2013 14:36:30 -0300 From: Mauro Carvalho Chehab MIME-Version: 1.0 To: Laurent Pinchart CC: linux-media@vger.kernel.org Subject: Re: [GIT PULL FOR v3.10] Camera sensors patches References: <3775187.HOcoQVPfEE@avalon> <8085333.TIMqcSUBaO@avalon> <20130415094248.2272db90@redhat.com> <1471330.zeTIWizKy8@avalon> In-Reply-To: <1471330.zeTIWizKy8@avalon> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Em 16-04-2013 12:30, Laurent Pinchart escreveu: > Hi Mauro, > > On Monday 15 April 2013 09:42:48 Mauro Carvalho Chehab wrote: >> Em Mon, 15 Apr 2013 12:19:23 +0200 Laurent Pinchart escreveu: >>> On Sunday 14 April 2013 16:59:58 Mauro Carvalho Chehab wrote: >>>> Em Fri, 12 Apr 2013 11:13:06 +0200 Laurent Pinchart escreveu: >>>>> Hi Mauro, >>>>> >>>>> The following changes since commit >>> >>> 81e096c8ac6a064854c2157e0bf802dc4906678c: >>>>> [media] budget: Add support for Philips Semi Sylt PCI ref. design >>>>> >>>>> (2013-04-08 07:28:01 -0300) >>>>> >>>>> are available in the git repository at: >>>>> git://linuxtv.org/pinchartl/media.git sensors/next >>>>> >>>>> for you to fetch changes up to > c890926a06339944790c5c265e21e8547aa55e49: >>>>> mt9p031: Use the common clock framework (2013-04-12 11:07:07 +0200) >>>>> >>>>> ---------------------------------------------------------------- >>>>> >>>>> Laurent Pinchart (5): >>>>> mt9m032: Fix PLL setup >>>>> mt9m032: Define MT9M032_READ_MODE1 bits >>>>> mt9p031: Use devm_* managed helpers >>>>> mt9p031: Add support for regulators >>>>> mt9p031: Use the common clock framework >>>> >>>> Hmm... It seems ugly to have regulators and clock framework and other >>>> SoC calls inside an i2c driver that can be used by a device that doesn't >>>> have regulators. >>>> >>>> I'm not sure what's the best solution for it, so, I'll be adding those >>>> two patches, but it seems that we'll need to restrict the usage of those >>>> calls only if the caller driver is a platform driver. >>> >>> The MT9P031 needs power supplies and a clock on all platforms, regardless >>> of the bridge bus type. >> >> Well, all digital devices require clock and power. If power is either a >> simple electric circuit, a battery or a regulator, that depends on the >> board. >> >>> I suppose the use case that mostly concerns you here is >>> USB webcams >> >> Yes. >> >>> where the power supplies and the clock are controlled automatically by the >>> device. >> >> Or could be not controlled at all. It could be a simple XTAL attached to the >> sensor or a clock signal provided by the bridge obtained from a fixed XTAL, >> and a resistor bridge or a Zenner diode providing the needed power voltage. >> >>> If we ever need to support such a device in the future we can of course >>> revisit the driver then, and one possible solution would be to register >>> fixed voltage regulators and a fixed clock. >> >> That is an overkill: devices were the power supply/xtal clock can't be >> controlled should not require extra software that pretend to control it. > > If I'm not mistaken that's however the recommended way on embedded devices at > the moment. I don't have a strong opinion on the subject for now, but this > will need to be at least discussed with core clock and regulator developers. Well, a customer's webcam is not an embedded device at all. That's why I think that putting it at the I2C driver is wrong: those drivers are not to be used only by embedded hardware. Regards, Mauro >