Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760349Ab3HOHJo (ORCPT ); Thu, 15 Aug 2013 03:09:44 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:60382 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752765Ab3HOHJm (ORCPT ); Thu, 15 Aug 2013 03:09:42 -0400 Date: Thu, 15 Aug 2013 00:09:38 -0700 From: Brian Norris To: Caizhiyong Cc: Andrew Morton , Karel Zak , "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "Wanglin (Albert)" , Artem Bityutskiy , Shmulik Ladkani , Huang Shijie Subject: Re: [PATCH] block: add command line partition parser Message-ID: <20130815070938.GB24007@brian-ubuntu> References: <20130805152206.76462cc4a42e51b16a0532f1@linux-foundation.org> <20130814155742.d3cd651e40e552696667e4f2@linux-foundation.org> <20130815050007.GA23474@brian-ubuntu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Content-Length: 6698 Lines: 141 On Thu, Aug 15, 2013 at 06:16:04AM +0000, Caizhiyong wrote: > > -----Original Message----- > > From: Brian Norris [mailto:computersforpeace@gmail.com] > > Sent: Thursday, August 15, 2013 1:00 PM > > To: Caizhiyong > > Cc: Andrew Morton; Karel Zak; linux-mtd@lists.infradead.org; > > linux-kernel@vger.kernel.org; Wanglin (Albert); Artem Bityutskiy; Shmulik Ladkani; > > Huang Shijie > > Subject: Re: [PATCH] block: add command line partition parser > > > > On Thu, Aug 15, 2013 at 03:38:47AM +0000, Caizhiyong wrote: > > > > -----Original Message----- > > > > From: Brian Norris [mailto:computersforpeace@gmail.com] > > > > Sent: Thursday, August 15, 2013 8:12 AM > > > > To: Andrew Morton > > > > Cc: Caizhiyong; Karel Zak; linux-mtd@lists.infradead.org; > > > > linux-kernel@vger.kernel.org; Wanglin (Albert); Artem Bityutskiy; Shmulik > > Ladkani; > > > > Huang Shijie > > > > Subject: Re: [PATCH] block: add command line partition parser > > > > > > > > On Wed, Aug 14, 2013 at 3:57 PM, Andrew Morton > > > > wrote: > > > > > On Tue, 13 Aug 2013 06:02:17 +0000 Caizhiyong wrote: > > > > > > > > > >> move the command line parser to a separate module, and change it into > > > > >> library-style code. > > > > >> > > > > >> reference: https://lkml.org/lkml/2013/8/6/550 > > > > > > > > The most recent patch is an addendum to this linked patch then? > > > > > > > > > Well OK. But to prove the library's usefulness and to generally clean > > > > > up the kernel, someone needs to sign up to the task of converting > > > > > drivers/mtd/cmdlinepart.c to use this code. > > > > > > > > > > I've been hopefully cc'ing various MTD people but am not being > > > > > overwhelmed with waves of enthusiasm ;) > > > > > > > > "I've been" implies that you have done so prior to this email. And > > > > "people" implies more than one person. I see that you CC'd David > > > > Woodhouse over a week ago, but he's fairly silent these days on MTD > > > > things. It's Artem or me who handle most of the day-to-day of MTD. And > > > > this is the first time I've seen this! (BTW, please include > > > > linux-mtd@lists.infradead.org for anything involving MTD.) > > > > > > > > This seems reasonable, and I'd be willing to work with this proposal. > > > > > > > > Caizhiyong, can you submit a clear single patch (or series of > > > > patches), CC'd to linux-mtd at least? Then we can see about supporting > > > > it in MTD. It doesn't look too difficult, but I need to check that it > > > > faithfully mimics the capability we currently rely on. There have been > > > > previous discussions on changing it, but this was rejected in favor of > > > > allowing more flexibility. Here's part of one such conversation: > > > > > > > > http://lists.infradead.org/pipermail/linux-mtd/2012-August/043599.html > > > > http://lists.infradead.org/pipermail/linux-mtd/2012-September/043825.html > > > > http://lists.infradead.org/pipermail/linux-mtd/2012-December/045322.html > > > > > > > > So I would recommend: > > > > (1) consider carefully the implications of your command-line format > > > > now, rather than later > > > > (2) if you want MTD to use it, it needs to support the features we use now > > > > > > It is fully functional reference MTD, :-). > > > > I realize that. I just want to be clear that we have to reconcile (1) > > and (2). IOW, if block device requirements stray too far from MTD > > requirements, then we might as well drop the idea of integration now. > > But if they agree, then we can move forward. > > > > > > Some particular cases to consider: overlapping partitions (how do > > > > block devices handle overlapping partitions?), out-of-order > > > > specification, zero sized partitions, mixed syntax (some specified > > > > with an offset, some not), multiple '-' partitions. > > > > > > I think the 'offset' just is used to hide some MTD space. > > > > No, it specifies offset as a distance from the beginning of the flash, > > so partitions can be numbered out of order. This is intentionally > > utilized by some users, for example, to ensure that a particular > > partition is always /dev/mtd0, even if it is not the first partition > > physically. > > > > > There are two way: > > > 1) redefine the 'offset' as a gap between forward partition and next partition. > > > 2) add code forbid command line partitions overlapping and out-of-order. > > > > > > I recommend 1), it seems to solve those problem(overlapping and out-of-order), > > but it will affect habit. > > > > The linked discussion is where MTD settled on retaining old practice. I > > brought it up not so that we change it here, but so that you would > > understand what you are agreeing to if you adopt a common MTD and block > > device parsing infrastructure. > > > > [Note that I am much less familiar with block device mechanics than with > > MTD.] Are any of the problem areas I mentioned actually forbidden on > > block devices? I know, for instance, that an MBR partition table can > > specify partitions out of order. And I've googled around and seen some > > posts about people (unintentionally) ending up with overlapping hard > > disk partitions. > > > > So from my primitive knowledge, it sounds like a block devices parser > > could agree with the same principle put forward by Shmulik in that > > second URL: > > > > "So far, mtdparts commandline parsing has been very lenient and liberal. > > I think we should keep this approach; give the user the flexibility, > > he'll be responsible to provide meaningful cmdline parts for his > > system." > > > > Brian > > I want to use the MTD command line partition method on block devices (eMMC). > It is very suitable for embedded systems. I think, in embedded system partition method, > if somebody need some feature on MTD device, he may be also need it on block device. > so I fully functional reference MTD command line partition. I agree. I'm curious: have you seen any need for a similar arrangement via device-tree? See, for example, drivers/mtd/ofpart.c. > I tested the out-of-order and overlapping on my system, used command line partition, It is work ok. > The block device code is not make any restrictions on partition out-of-order and overlapping. OK, good. Thanks for checking. > I hope extend the flexibility to block device. Sure. I'll try to review the full patch soon and test out integrating it with MTD. Thanks, Brian -- 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/