mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-05 05:09:17 -04:00
9fb4ab4d3d
Next record calucaltion can be reduced to a much more tivial ALIGN operation as follows: 1. Splitting 5 into 2 + 3 we get next = ((be16_to_cpu(rec->len) + 2 + 3) & ~3) - 2 (1) 2. Using ALIGN macro we reduce (1) to: ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2 (2) 3. Subsituting 'next' in original next record calucation we get: (void *)&rec->data[ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2] (3) 4. Converting array index to pointer arithmetic we convert (3) into: (void *)rec + sizeof(*rec) + ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2 (4) 5. Subsituting sizeof(*rec) with its value, 6, and substracting 2, in (4) we get: (void *)rec + ALIGN(be16_to_cpu(rec->len) + 2, 4) + 4 (5) 6. Since ALIGN(X, 4) + 4 == ALIGN(X + 4, 4), (5) can be converted to: (void *)rec + ALIGN(be16_to_cpu(rec->len) + 6, 4) (6) 5. Subsituting 6 in (6) to sizeof(*rec) we get: (void *)rec + ALIGN(be16_to_cpu(rec->len) + sizeof(*rec), 4) (7) Using expression (7) should make it more clear that next record is located by adding full size of the current record (payload + auxiliary data) aligned to 4 bytes, to the location of the current one. No functional change intended. Cc: Chris Healy <cphealy@gmail.com> Cc: Kyle McMartin <kyle@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-kernel <linux-kernel@vger.kernel.org> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.