Re: [PATCH 1/1] mtd/intel-spi: Support cmdline-based partition

[Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>]

On Mon, 27 Apr 2020 11:16:23 +0200
Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> wrote:

> Hi all,
> 
> On Wed, 1 Apr 2020 09:41:48 +0200
> Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:
> 
> > Hi ron,
> > 
> > ron minnich <rminnich@xxxxxxxxx> wrote on Mon, 30 Mar 2020 08:53:22
> > -0700:
> >   
> > > On Mon, Mar 30, 2020 at 12:27 AM Miquel Raynal
> > > <miquel.raynal@xxxxxxxxxxx> wrote:
> > >     
> > > > Would it be hard to support an extra ':' after the MTD device name?
> > > > This way would would allow anything inside the optional '(' ')' but
> > > > would keep the trailing ':'.
> > > >
> > > > toTay:
> > > >         mtdparts=name:part1,part2
> > > >
> > > > So:
> > > >         mtdparts=(0000:00:1f.5):25165824(BIOS),-(squashfs)      
> > > 
> > > 
> > > I thought about that ':' too. It does add a bit more to the code, and
> > > a bit more in the way of error cases. I always worry, when code is
> > > going into flash,
> > > about errors where something looks close to right but is wrong. (says
> > > the person who just typed it instead of is a few times :-)
> > > 
> > > What if we did this:
> > > mtdparts=[0000:00:1f.5]25165824(BIOS),-(squashfs)
> > > 
> > > Is the "]" 'enough different' that we do not need the ':'?
> > > 
> > > I kind of like the [] better anyway as it makes the mtdid stand out a
> > > bit more from the part names? But is it enough that we don't need the
> > > ':'? Would you still prefer the () as opposed to the []?    
> > 
> > I like the [] as well, maybe more than () because at least it does not
> > conflict with the partition names. But I really prefer keeping the : if
> > the code is still readable.
> > 
> > It is much easier to explain to people : "if you have a : in the name,
> > enclose it with []".  
> 
> Sorry to chime in so late in the discussion, but I wonder if any of
> that is necessary. Can't we just split the string per device (split
> strings every time we see a ';'), and then find the last ':' in each of
> those strings and consider everything before that last ':' to be the MTD
> name. That should work even if the MTD name contains one or more ':'.
> 
> Don't get me wrong, I'm perfectly fine with intel enclosing the PCI
> address in [] to make it clearer, but I see that other drivers use ':'
> in their MTD device names (the atmel raw NAND controller driver to name
> one), so I think it'd be good to make the mtd part parsing robust to
> this use case.

I just gave it a try and the following patch should solve the problem
(only compile-tested). As I said previously, it doesn't prevent you from
enclosing the PCI address in [] if you think it's clearer, but I think
the problem should be addressed in the cmdline parser anyway.

--->8---
>From 08b30597dd73efd9c4c8d1906ab02a9540875419 Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Date: Mon, 27 Apr 2020 11:44:50 +0200
Subject: [PATCH] mtd: parser: cmdline: Support MTD names containing one or
 more colons

Looks like some drivers define MTD names with a colon in it, thus
making mtdpart= parsing impossible. Let's fix the parser to gracefully
handle that case: the last ':' in a partition definition sequence is
considered instead of the first one.

Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
---
 drivers/mtd/parsers/cmdlinepart.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/parsers/cmdlinepart.c b/drivers/mtd/parsers/cmdlinepart.c
index c86f2db8c882..0625b25620ca 100644
--- a/drivers/mtd/parsers/cmdlinepart.c
+++ b/drivers/mtd/parsers/cmdlinepart.c
@@ -218,12 +218,29 @@ static int mtdpart_setup_real(char *s)
 		struct cmdline_mtd_partition *this_mtd;
 		struct mtd_partition *parts;
 		int mtd_id_len, num_parts;
-		char *p, *mtd_id;
+		char *p, *mtd_id, *semicol;
+
+		/*
+		 * Replace the first ';' by a NULL char so strrchr can work
+		 * properly.
+		 */
+		semicol = strchr(s, ';');
+		if (semicol)
+			*semicol = '\0';
 
 		mtd_id = s;
 
-		/* fetch <mtd-id> */
-		p = strchr(s, ':');
+		/*
+		 * fetch <mtd-id>. We use strrchr to ignore all ':' that could
+		 * be present in the MTD name, only the last one is interpreted
+		 * as an <mtd-id>/<part-definition> separator.
+		 */
+		p = strrchr(s, ':');
+
+		/* Restore the ';' now. */
+		if (semicol)
+			*semicol = ';';
+
 		if (!p) {
 			pr_err("no mtd-id\n");
 			return -EINVAL;

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