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Message-ID: <87setej1y2.fsf@prevas.dk>
Date: Wed, 02 Oct 2024 11:20:37 +0200
From: Rasmus Villemoes <linux@...musvillemoes.dk>
To: Andy Shevchenko <andy@...nel.org>
Cc: Christian Marangi <ansuelsmth@...il.com>, Jens Axboe <axboe@...nel.dk>,
Jonathan Corbet <corbet@....net>, Ulf Hansson <ulf.hansson@...aro.org>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Kees Cook <kees@...nel.org>, Daniel
Golle <daniel@...rotopia.org>, INAGAKI Hiroshi
<musashino.open@...il.com>, Christian Brauner <brauner@...nel.org>, Al
Viro <viro@...iv.linux.org.uk>, Li Lingfeng <lilingfeng3@...wei.com>,
Ming Lei <ming.lei@...hat.com>, Christian Heusel <christian@...sel.eu>,
linux-block@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
devicetree@...r.kernel.org, linux-hardening@...r.kernel.org, Miquel
Raynal <miquel.raynal@...tlin.com>, Lorenzo Bianconi
<lorenzo@...nel.org>, upstream@...oha.com
Subject: Re: [PATCH v4 0/5] block: partition table OF support
Andy Shevchenko <andy@...nel.org> writes:
> On Mon, Sep 30, 2024 at 01:30:07PM +0200, Christian Marangi wrote:
>> Hi,
>> this is an initial proposal to complete support for manually defining
>> partition table.
>>
>>
>> Some block device also implement boot1 and boot2 additional disk. Similar
>> to the cmdline parser, these disk can have OF support using the
>> "partitions-boot0" and "partitions-boot1" additional node.
>>
>> It's also completed support for declaring partition as read-only as this
>> feature was introduced but never finished in the cmdline parser.
>
>
> I'm not sure I fully understood the problem you are trying to solve.
> I have a device at hand that uses eMMC (and was produced almost ten years ago).
> This device has a regular GPT on eMMC and no kernel needs to be patched for that.
> So, why is it a problem for the mentioned OEMs to use standard GPT approach?
For the user area (main block device), yes, a GPT can often be used, but
not always. For the boot partitions, the particular SOC/cpu/bootrom may
make it impossible to use a standard partition table, because the
bootrom expects to find a bootloader at offset 0 on the active boot
partition. In such a case, there's no way you can write a regular MBR or
GPT, but it is nevertheless nice to have a machine-readable definition
of which data goes where in the boot partitions. With these patches, one
can do
partitions-boot0 {
partition@0 {
label = "bootloader";
reg = <0 0x...>; // 2 MB
}
partition@... {
label = "device-data";
reg = <...> // 4 MB
}
}
and describe that layout.
Rasmus
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