From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dmitry Osipenko <digetx@gmail.com>
Subject: Re: [PATCH v1] partitions/efi: Add 'gpt_sector' kernel cmdline
 parameter
Date: Wed, 19 Feb 2020 19:38:30 +0300
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 <20200219162738.GA10644@infradead.org>
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To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>, Davidlohr Bueso <dave@stgolabs.net>, Colin Cross <ccross@android.com>, Thierry Reding <thierry.reding@gmail.com>, Jonathan Hunter <jonathanh@nvidia.com>, =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <mirq-linux@rere.qmqm.pl>, David Heidelberg <david@ixit.cz>, Peter Geis <pgwipeout@gmail.com>, linux-efi@vger.kernel.org, linux-tegra@vger.kernel.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
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19.02.2020 19:27, Christoph Hellwig пишет:
> On Wed, Feb 19, 2020 at 07:23:39PM +0300, Dmitry Osipenko wrote:
>> The gpt_sector=<sector> causes the GPT partition search to look at the
>> specified sector for a valid GPT header if the GPT is not found at the
>> beginning or the end of block device.
>>
>> In particular this is needed for NVIDIA Tegra consumer-grade Android
>> devices in order to make them usable with the upstream kernel because
>> these devices use a proprietary / closed-source partition table format
>> for the EMMC and it's impossible to change the partition's format. Luckily
>> there is a GPT table in addition to the proprietary table, which is placed
>> in uncommon location of the EMMC storage and bootloader passes the
>> location to kernel using "gpt gpt_sector=<sector>" cmdline parameters.
>>
>> This patch is based on the original work done by Colin Cross for the
>> downstream Android kernel.
> 
> I don't think a magic command line is the way to go.  The best would be
> to reverse-engineer the proprietary partition table format.  If that is
> too hard we can at least key off the odd GPT location based of it's
> magic number.

I'll try to take a look at RE, pretty sure somebody tried to do that before.