From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754485Ab0IHQsx (ORCPT ); Wed, 8 Sep 2010 12:48:53 -0400 Received: from smtp-out.google.com ([216.239.44.51]:34340 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751287Ab0IHQsv (ORCPT ); Wed, 8 Sep 2010 12:48:51 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=MUg8nIRslT+GnW+bL3va/c4OEKon6o+VIT0SHioHoD2jfNDsSJ5CJwpHsInRE2YWz7 jxXH02nkpfQNfb5Z1Zqg== MIME-Version: 1.0 In-Reply-To: <20100908155721.GD23745@lixom.net> References: <20100818041333.GA14149@lixom.net> <20100818171636.0625b668.akpm@linux-foundation.org> <20100819032230.GA21980@lixom.net> <20100820010242.GA29588@lixom.net> <20100820221323.GC8535@lixom.net> <20100908145705.GC23745@lixom.net> <20100908155721.GD23745@lixom.net> Date: Wed, 8 Sep 2010 09:48:46 -0700 Message-ID: Subject: Re: [PATCH v3] mmc: add config and runtime option for number of mmcblk minors From: Colin Cross To: Olof Johansson Cc: Kay Sievers , Lei Wen , Andrew Morton , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, Mandeep Baines Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 8, 2010 at 8:57 AM, Olof Johansson wrote: > On Wed, Sep 08, 2010 at 05:19:25PM +0200, Kay Sievers wrote: >> On Wed, Sep 8, 2010 at 16:57, Olof Johansson wrote: >> > On Wed, Sep 08, 2010 at 10:25:58PM +0800, Lei Wen wrote: >> > >> >> The patch's purpose is good. As modern sd&mmc is used to host the file >> >> system, the 8 partition limitation is becoming a kind of bottleneck... >> >> But why not just add GENHD_FL_EXT_DEVT flag to allow mmc use extended >> >> partition numbers? >> > >> > No need to quote the whole patch next time. :) >> > >> > Given that MMC is sometimes used in deeply embedded environments where >> > udev might not be running to take care of dynamic device numbering, >> > I chose to stay with a static layout. >> > >> > I could be convinced otherwise though. It would cause some additional >> > hassles for me since we start udev lateish during boot and have a >> > prepopulated /dev before that, but that can be dealt with. >> >> I think the extended number are only used for stuff larger than the static 8? > > Ah, yes, of course. > >> Apart from that, you can not reliably or securely use a static /dev >> these days, you never know which device you talk to, because the >> kernel has far too many dynamically assigned numbers. For that reason, >> most embedded setups use the busybox hack to populate /dev. Recent >> kernels have a devfs again, and there is no reason today to continue >> any static /dev experiments -- unless someone is going over the entire >> tree and fixes all the dynamic assignments, which is unlikely to >> happen ever. > > Yeah, it's a weak argument but I wanted to go for the least surprising > one for anyone who still relies on static numbering of mmc, since it's > used as root device, etc. > > But with the first 8 minors being the same as before, there's little > reason to care about that -- the EXT_DEVT approach will actually be > the smaller change, since it won't renumber anything, just extend in a > different part of the address space. > > Lei, want to submit a proper patch for it to replace mine? I have a tested patch for this. It also cleans up the connection between devidx and minor numbers. I'll send it shortly.