From: Stephen Warren <swarren@wwwdotorg.org>
To: Christoph Hellwig <hch@infradead.org>,
Dmitry Osipenko <digetx@gmail.com>
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>,
"Michał Mirosław" <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
Subject: Re: [PATCH v1] partitions/efi: Add 'gpt_sector' kernel cmdline parameter
Date: Wed, 19 Feb 2020 09:59:54 -0700 [thread overview]
Message-ID: <f9e41108-7811-0deb-6977-be0f60e23b52@wwwdotorg.org> (raw)
In-Reply-To: <20200219162738.GA10644@infradead.org>
On 2/19/20 9:27 AM, Christoph Hellwig wrote:
> 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 thought that the backup GPT was always present in the standard
location; it's just the primary GPT that's in an odd location. So, this
kernel parameter just forces the kernel to look first for the primary
GPT in the unusual location, thus avoiding an error message when that's
not there, and the system falls back to the backup GPT.
Or, do I misremember the layout, or the kernel's behaviour if primary
GPT is missing?
next prev parent reply other threads:[~2020-02-19 17:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 16:23 [PATCH v1] partitions/efi: Add 'gpt_sector' kernel cmdline parameter Dmitry Osipenko
2020-02-19 16:26 ` Ard Biesheuvel
2020-02-19 16:36 ` Dmitry Osipenko
2020-02-19 16:27 ` Christoph Hellwig
2020-02-19 16:38 ` Dmitry Osipenko
2020-02-19 16:59 ` Stephen Warren [this message]
2020-02-19 17:44 ` Dmitry Osipenko
2020-02-24 16:33 ` Karel Zak
2020-02-24 17:23 ` Dmitry Osipenko
2020-02-24 18:22 ` Dmitry Osipenko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f9e41108-7811-0deb-6977-be0f60e23b52@wwwdotorg.org \
--to=swarren@wwwdotorg.org \
--cc=axboe@kernel.dk \
--cc=ccross@android.com \
--cc=dave@stgolabs.net \
--cc=david@ixit.cz \
--cc=digetx@gmail.com \
--cc=hch@infradead.org \
--cc=jonathanh@nvidia.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-efi@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tegra@vger.kernel.org \
--cc=mirq-linux@rere.qmqm.pl \
--cc=pgwipeout@gmail.com \
--cc=thierry.reding@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).