From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f54.google.com (mail-pb0-f54.google.com [209.85.160.54]) by yocto-www.yoctoproject.org (Postfix) with ESMTP id B2AFAE01575 for ; Wed, 14 Aug 2013 07:28:09 -0700 (PDT) Received: by mail-pb0-f54.google.com with SMTP id ro12so9426687pbb.41 for ; Wed, 14 Aug 2013 07:28:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :cc:subject:references:in-reply-to:content-type :content-transfer-encoding; bh=CjC65+zdfhBtgybthkooAHj1+YIRDBJ1uFpPlWz6xms=; b=lnfoLQWOZF+ISVnKTFAfsjUPmpf0iTeleoIEpqstuh5QP3Vb0f85cGJ4h0LtMkduDZ w9bBlOkZ64K4b1Am6aJhKgVGdbwyc4KtWAcUnMnG4JmVYmwIaf/52IdfvjNPp5BFuVlN KeWMLMksvU5vhamiguxse4ySWI+CRgydzVuvfw553O6d2zj+yr+0zyl8RVvlSL6BQddp tVMlYMokaTFZ7JCKuj5lnM/rIn15XxXV1Cu8NV9RdpEYdPa02YXvRib1Oh6htRshx0gO z3wbhDtLJF7Y6vkfSzr2qudeBdJOj/AdinVWYpXFmFaPB7XIgT7XXCfzXe1v12+EeNOS azog== X-Gm-Message-State: ALoCoQnYE2xF5C4Vtofvw/o7EiI3ZItxZGkiIul03oLhBEpvJgNzlSWl7qYRrkzVhuJm6DE+OTfb X-Received: by 10.66.179.143 with SMTP id dg15mr10250417pac.52.1376490488889; Wed, 14 Aug 2013 07:28:08 -0700 (PDT) Received: from [192.168.1.8] (ip98-167-230-131.ph.ph.cox.net. [98.167.230.131]) by mx.google.com with ESMTPSA id mz5sm19858960pbc.18.2013.08.14.07.28.06 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 14 Aug 2013 07:28:07 -0700 (PDT) Message-ID: <520B93F4.9060306@boundarydevices.com> Date: Wed, 14 Aug 2013 07:28:04 -0700 From: Eric Nelson User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: Thanassis Silis References: , <520A7B28.3000604@boundarydevices.com> In-Reply-To: Cc: "meta-freescale@yoctoproject.org" Subject: Re: speed of /dev/i2c-2 in imx6q sabre-lite X-BeenThere: meta-freescale@yoctoproject.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Usage and development list for the meta-fsl-* layers List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 Aug 2013 14:28:14 -0000 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Thanassis, On 08/14/2013 05:25 AM, Thanassis Silis wrote: > Eric, > thank you very much for the answer (I have compiled kernel 3.0.35_1.1.0 > by the way, but the code hasn't changed since then). > I do have a question (in my limited kernel knowledge) :) > https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_4.0.0/drivers/i2c/busses/i2c-imx.c#L63 > > this looks like a module, but as I see in my sabrelite's > /lib/modules/3.0.35-1.1.0+g2dc5560 > modules.builtin:92:kernel/drivers/i2c/busses/i2c-imx.ko > it is built in the kernel. > > What is the purpose of i2c-imx and how does it relate to imx* boards? > i2c-imx is the device driver for the i2c part on many i.MX processors, including i.MX6. Because it's needed for many internal operations, we compile it into the kernel, instead of as a separately loadable module. This is a bit of "kernel configuration 101", but when you configure drivers into the Linux kernel, you can generally choose either "*" or "M", shown as "y" or "m" in the .config file: https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_4.0.0/arch/arm/configs/nitrogen6x_defconfig#L144 When you choose '*' or 'y', the driver is included in the kernel itself (uImage on our normal usage). If you choose 'm', the external .ko file is built. This is mostly important at startup, since you have to have a working filesystem and utilities like 'modprobe' or 'insmod' to load a .ko file. Regards, Eric