linux-kernel - Re: [PATCH] mtd: rawnand: ams-delta: Drop board specific partition info

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Date:   Sun, 24 Mar 2019 17:48:22 +0100
From:   Janusz Krzysztofik <jmkrzyszt@...il.com>
To:     Aaro Koskinen <aaro.koskinen@....fi>
Cc:     Boris Brezillon <bbrezillon@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Tony Lindgren <tony@...mide.com>,
        linux-mtd@...ts.infradead.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Janusz Krzysztofik <jmkrzyszt@...il.com>
Subject: Re: [PATCH] mtd: rawnand: ams-delta: Drop board specific partition info

Hi Aaro,

Thanks for your review.

On Wednesday, March 20, 2019 2:16:30 AM CET Aaro Koskinen wrote:
> On Tue, Mar 19, 2019 at 11:37:18PM +0100, Janusz Krzysztofik wrote:
> > After recent modifications, only a hardcoded partition info makes
> > the driver device specific.  Other than that, the driver uses GPIO
> > exclusively and can be used on any hardware.
> > 
> > Drop the partition info and use MTD partition parser with default
> > list of partition types instead.
> > 
> > Amstrad Delta users should append the followig partition info to their
>                                         ^^^^^^^^
> Should be "following".
> 
> > kernel command line, possibly by embedding it in CONFIG_CMDLINE:
> > mtdparts=ams-delta-nand:3584k(Kernel),256k(u-boot),256k(u-boot_params),\
> > 256k(Amstrad_LDR),27m(File_system),768k(PBL_reserved).  For their
> > convenience, select CONFIG_MTD_CMDLINE_PARTS  symbol from that board
> > Kconfig automatically if this NAND driver is also selected.
> > 
> > Signed-off-by: Janusz Krzysztofik <jmkrzyszt@...il.com>
> > Cc: Tony Lindgren <tony@...mide.com>
> 
> Could we move the fixed partition setup to the board file
> instead? Otherwise this kind of change is not really nice for the users,
> as it will likely break existing setups. The default partition layout
> should remain the same.

I'm wondering if it would be acceptable to pass partition info from a .dts 
file.  I think that would be a better, more modern approach than adding a new 
header under include/linux/platform_data.

The problem with a device tree based implementation is, I know of no u-boot 
version supporting both Amstrad Delta and FDT.  However, I've already tested 
two solutions that work for me.

One uses CONFIG_ARM_APPENDED_DTB and requires a user to manually append the 
blob to zImage and (re)generate uImage.  I'm not sure how much more user-
friendly it looks for you, compared to the command line version I proposed 
initially.

If the above is not acceptable. I can propose still another approach. The blob 
is automagically built and embedded into the kernel with some assembler glue, 
then unflattened from the board init_machine(), somehow similar to the way 
drivers/of/unittest.c does it.

Please advise which approach sounds best to you (platform_data, 
CONFIG_ARM_APPENDED_DTB or unittest like).

Thanks,
Janusz

> 
> A.
>