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SD spec v5.1 adds discard support. The flows and commands are similar to mmc, so just set the discard arg in CMD38. A host which supports DISCARD shall check if the DISCARD_SUPPORT (b313) is set in the SD_STATUS register. If the card does not support discard, the host shall not issue DISCARD command, but ERASE command instead. Post the DISCARD operation, the card may de-allocate the discarded blocks partially or completely. So the host mustn't make any assumptions concerning the content of the discarded region. This is unlike ERASE command, in which the region is guaranteed to contain either '0's or '1's, depends on the content of DATA_STAT_AFTER_ERASE (b55) in the scr register. One more important difference compared to ERASE is the busy timeout which we will address on the next patch. Signed-off-by: Avri Altman <avri.altman@wdc.com> Signed-off-by: Ulf Hansson <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.