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In the SD spec v4.0 the CMD48/49 and CMD58/59 were introduced as optional commands. In the SD spec v4.1 the SD function extension registers were introduced, which requires support for CMD48/49/58/59 to be read/written from/to. Moreover, a specific function extension register were added to let the card announce support for optional features in regards to power management. The features that were added are "Power Off Notification", "Power Down Mode" and "Power Sustenance". As a first step to support this, let's read and parse the register for power management during the SD card initialization and store the information about the supported features in the struct mmc_card. In this way, we prepare for subsequent changes to implement the complete support for the new features. Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com> Acked-by: Avri Altman <avri.altman@wdc.com> Link: https://lore.kernel.org/r/20210504161222.101536-10-ulf.hansson@linaro.org
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.