RE: [PATCH] block: add command line partition parser

[Caizhiyong <caizhiyong@huawei.com>]

> -----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
> <akpm@linux-foundation.org> wrote:
> > On Tue, 13 Aug 2013 06:02:17 +0000 Caizhiyong <caizhiyong@huawei.com> 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, :-).

> 
> 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.
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.

> 
> Anyway, if you resend, we can review.
> 
> Thanks,
> Brian