Re: [PATCH v1] partitions/efi: Add 'gpt_sector' kernel cmdline parameter

From: Christoph Hellwig
Date: Wed Feb 19 2020 - 11:27:55 EST

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.