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From: ron minnich <rminnich@gmail.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-mtd@lists.infradead.org
Subject: Re: [PATCH 1/1] mtd/intel-spi: Support cmdline-based partition
Date: Fri, 27 Mar 2020 10:05:52 -0700
Message-ID: <CAP6exYJ4-pBBZKA0z8TKPqh_0tKzJadjXEBZk9dc9ij8BJ9Xew@mail.gmail.com> (raw)
In-Reply-To: <20200327175238.784cf47c@xps13>

I did try the \ thing but found it a bit tricky to work with, with
lots of potential for simple errors.

It would require cmdlines like this
mtdparts=0000\:00\:0.1f:etcetc

A lot of these mtdparts definitions are produced by scripts and
Makefiles and there are many, many places where \\ have a way of
vanishing.

We talked here about an option where the name would be in parens or brackets:
mtdparts=(00:00:0.0):etcetc

which I think looks a lot nicer but and leaves room for growth, where
in a few years some other strange name comes along that might break
our rules. () anyone?

Another problem is, the name matching is a strcmp. There's no
semantics in the names. So where, technically, these  PCI addresses
are the same:
1f.3 and 0:1f.3 and  0:0:1f.3 and  0000:00:1f.3
the strcmp would fail between 1f.3 and 0000:00:1f.3 -- but they're the same.

This means that the PCI names must be strongly structured: they must
follow the rules such that the : and . occur in a fixed place in the
string, meaning determining that a string is a PCI TBDF is relatively
simple.

So I keep coming back to the simple "name matches pattern ****:**:*.*
(where * means any char) -- it's a PCI address" as maybe the easiest
thing to do.
But possibly the () are the best future-proofing. I really am not a fan of \.

ron

On Fri, Mar 27, 2020 at 9:52 AM Miquel Raynal <miquel.raynal@bootlin.com> wrote:
>
> Hi Mika,
>
> Mika Westerberg <mika.westerberg@linux.intel.com> wrote on Fri, 27 Mar
> 2020 18:48:02 +0200:
>
> > On Fri, Mar 27, 2020 at 05:19:07PM +0100, Miquel Raynal wrote:
> > > Hi Mika,
> > >
> > > Mika Westerberg <mika.westerberg@linux.intel.com> wrote on Fri, 27 Mar
> > > 2020 17:56:08 +0200:
> > >
> > > > Hi,
> > > >
> > > > I don't think it is good idea to change PCI device name like that.
> > > >
> > > > Instead the MTD cmdline parser should be teach to handle names like this
> > > > properly.
> > >
> > > It is a bit more complicated than that since parsers have been using
> > > this syntax for a long time and, more importantly, it means
> > > potentially updating all bootloaders.
> > >
> > > I am not against updating the parser, but the s/:/|/ solution proposed
> > > before is rather undescriptive and it is hard to find an alternative
> > > character that would have a meaning here.
> >
> > I'm completely unfamiliar with these but would escape char work here? I
> > mean if you want ":" to be parsed literally then you pass "\:" in the
> > command line. That should work with the existing and also allow
> > supporting SPI NOR controllers on PCI bus.
>
> We would still have to update bootloaders code but that would be easy
> to handle. The logic being "search for the next ':', when you have one
> check if there is a '\' in front of it. If yes, search again". Why
> not... This also means reconstructing the name by dropping manually the
> additional '\' in Linux.
>
> Thanks,
> Miquèl

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Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-23 19:58 ron minnich
2020-03-23 23:19 ` ron minnich
2020-03-25 17:34   ` ron minnich
2020-03-25 17:34     ` ron minnich
2020-03-27 15:48       ` ron minnich
2020-03-27 15:56         ` Mika Westerberg
2020-03-27 16:19           ` Miquel Raynal
2020-03-27 16:48             ` Mika Westerberg
2020-03-27 16:52               ` Miquel Raynal
2020-03-27 17:05                 ` ron minnich [this message]
2020-03-27 17:16                   ` Mika Westerberg
2020-03-27 17:39                     ` ron minnich
2020-03-27 23:53                       ` ron minnich
2020-03-30  6:08                         ` Mika Westerberg
2020-03-30  7:27                           ` Miquel Raynal
2020-03-30 15:53                             ` ron minnich
2020-04-01  7:41                               ` Miquel Raynal
2020-04-01 15:42                                 ` ron minnich
2020-04-01 19:49                                   ` ron minnich
2020-04-27  9:16                                 ` Boris Brezillon
2020-04-27  9:49                                   ` Boris Brezillon
2020-04-27 14:41                                     ` Miquel Raynal
2020-04-27 18:48                                       ` ron minnich
2020-04-27 18:50                                         ` ron minnich
2020-04-27 18:56                                           ` Miquel Raynal
2020-04-27 18:59                                             ` ron minnich
2020-04-27 19:21                                             ` Boris Brezillon
2020-04-27 19:31                                               ` ron minnich
2020-04-27 20:31                                     ` ron minnich
2020-04-27 21:20                                       ` Miquel Raynal
2020-03-27 16:53             ` ron minnich
2020-03-27 16:15         ` Miquel Raynal

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