[PATCH 1/7] doc: Migrate CodingStyle wiki page to Sphinx
Martin Bonner
martingreybeard at gmail.com
Mon Jul 11 21:02:47 CEST 2022
On // comments:
a) I thought I had read recently that they are now accepted.
b) Can we stop calling them "C++ style"? They have been legal in standard
C for all of this millennium! There are university graduates who were born
after // comments became legal in standard C.
c) If we don't currently accept them, can we change the style now (see
previous point)?
A response along the lines of "this is just moving the wiki into .rst files
- we can actually change things separately" would seem entirely reasonable.
Martin
On Mon, 11 Jul 2022 at 19:15, Tom Rini <trini at konsulko.com> wrote:
> Move the current CodingStyle wiki page to doc/develop/codingstyle.rst.
> The changes here are for formatting or slight rewording so that it reads
> well when linking to other Sphinx documents.
>
> Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
> Signed-off-by: Tom Rini <trini at konsulko.com>
> ---
> Changes in v2:
> - Assorted wiki -> Sphinx style corrections and a few typo fixes, per
> Heinrich
> ---
> doc/develop/codingstyle.rst | 255 ++++++++++++++++++++++++++++++++++++
> doc/develop/index.rst | 8 ++
> 2 files changed, 263 insertions(+)
> create mode 100644 doc/develop/codingstyle.rst
>
> diff --git a/doc/develop/codingstyle.rst b/doc/develop/codingstyle.rst
> new file mode 100644
> index 000000000000..bbeca42e656b
> --- /dev/null
> +++ b/doc/develop/codingstyle.rst
> @@ -0,0 +1,255 @@
> +.. SPDX-License-Identifier: GPL-2.0+:
> +
> +U-Boot Coding Style
> +===================
> +
> +The following Coding Style requirements shall be mandatory for all code
> contributed to
> +the U-Boot project.
> +
> +Exceptions are only allowed if code from other projects is integrated
> with no
> +or only minimal changes.
> +
> +The following rules apply:
> +
> +* All contributions to U-Boot should conform to the `Linux kernel
> + coding style <
> https://www.kernel.org/doc/html/latest/process/coding-style.html>`_
> + and the `Lindent script <
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/Lindent
> >`_.
> + * The exception for net files to the `multi-line comment
> + <
> https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting
> >`_
> + applies only to Linux, not to U-Boot. Only large hunks which are copied
> + unchanged from Linux may retain that comment format.
> +
> +* Use patman to send your patches (``tools/patman/patman -H`` for full
> + instructions). With a few tags in your commits this will check your
> patches
> + and take care of emailing them.
> +
> +* If you don't use patman, make sure to run ``scripts/checkpatch.pl``.
> For
> + more information, read :doc:`checkpatch`. Note that this should be done
> + *before* posting on the mailing list!
> +
> +* Source files originating from different projects (for example the MTD
> + subsystem or the hush shell code from the BusyBox project) may, after
> + careful consideration, be exempted from these rules. For such files, the
> + original coding style may be kept to ease subsequent migration to newer
> + versions of those sources.
> +
> +* Please note that U-Boot is implemented in C (and to some small parts in
> + Assembler); no C++ is used, so please do not use C++ style comments
> (//) in
> + your code.
> +
> + * The sole exception here is for SPDX tags in some files (checkpatch.pl
> will warn you).
> +
> +* Please also stick to the following formatting rules:
> +
> + * Remove any trailing white space
> +
> + * Use TAB characters for indentation and vertical alignment, not spaces
> +
> + * Make sure NOT to use DOS ``\r\n`` line feeds
> +
> + * Do not add more than 2 consecutive empty lines to source files
> +
> + * Do not add trailing empty lines to source files
> +
> + * Using the option ``git config --global color.diff auto`` will help to
> + visually see whitespace problems in ``diff`` output from ``git``.
> +
> + * In Emacs one can use ``=M-x whitespace-global-mode=`` to get visual
> + feedback on the nasty details. ``=M-x whitespace-cleanup=`` does The
> Right
> + Thing (tm)
> +
> +Submissions of new code or patches that do not conform to these
> requirements
> +shall be rejected with a request to reformat the changes.
> +
> +U-Boot Code Documentation
> +-------------------------
> +
> +U-Boot adopted the kernel-doc annotation style, this is the only
> exception from
> +multi-line comment rule of Coding Style. While not mandatory, adding
> +documentation is strongly advised. The Linux kernel `kernel-doc
> +<https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html>`_
> +documentation applies with no changes.
> +
> +Use structures for I/O access
> +-----------------------------
> +
> +U-Boot typically uses a C structure to map out the registers in an I/O
> region,
> +rather than offsets. The reasons for this are:
> +
> +* It dissociates the register location (offset) from the register type,
> which
> + means the developer has to make sure the type is right for each access,
> + whereas with the struct method, this is checked by the compiler;
> +
> +* It avoids actually writing all offsets, which is (more) error- prone;
> +
> +* It allows for better compile time sanity-checking of values we write to
> registers.
> +
> +Some reasons why you might not use C structures:
> +
> +* Where the registers appear at different offsets in different hardware
> + revisions supported by the same driver
> +
> +* Where the driver only uses a small subset of registers and it is not
> worth
> + defining a struct to cover them all, with large empty regions
> +
> +* Where the offset of a register might be hard to figure out when buried
> a long
> + way down a structure, possibly with embedded sub-structures
> +
> +* This may need to change to the kernel model if we allow for more
> run-time
> + detection of what drivers are appropriate for what we're running on.
> +
> +Please use check_member() to verify that your structure is the expected
> size,
> +or that particular members appear at the right offset.
> +
> +Include files
> +-------------
> +
> +You should follow this ordering in U-Boot. The common.h header (which is
> going
> +away at some point) should always be first, followed by other headers in
> order,
> +then headers with directories, then local files:
> +
> +.. code-block:: C
> +
> + #include <common.h>
> + #include <bootstage.h>
> + #include <dm.h>
> + #include <others.h>
> + #include <asm/...>
> + #include <arm/arch/...>
> + #include <dm/device_compat/.h>
> + #include <linux/...>
> + #include "local.h"
> +
> +Within that order, sort your includes.
> +
> +It is important to include common.h first since it provides basic
> features used
> +by most files, e.g. CONFIG options.
> +
> +For files that need to be compiled for the host (e.g. tools), you need to
> use
> +``#ifndef USE_HOSTCC`` to avoid including common.h since it includes a
> lot of
> +internal U-Boot things. See common/image.c for an example.
> +
> +If your file uses driver model, include <dm.h> in the C file. Do not
> include
> +dm.h in a header file. Try to use forward declarations (e.g. ``struct
> +udevice``) instead.
> +
> +Filenames
> +---------
> +
> +For .c and .h files try to use underscore rather than hyphen unless you
> want
> +the file to stand out (e.g. driver-model uclasses should be named
> xxx-uclass.h.
> +Avoid upper case and keep the names fairly short.
> +
> +Function and struct comments
> +----------------------------
> +
> +Non-trivial functions should have a comment which describes what they do.
> If it
> +is an exported function, put the comment in the header file so the API is
> in
> +one place. If it is a static function, put it in the C file.
> +
> +If the function returns errors, mention that and list the different
> errors that
> +are returned. If it is merely passing errors back from a function it
> calls,
> +then you can skip that.
> +
> +See `here
> +<
> https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#function-documentation
> >`_
> +for style.
> +
> +Driver model
> +------------
> +
> +When declaring a device, try to use ``struct udevice *dev``, i.e. ``dev``
> as the name:
> +
> +.. code-block:: C
> +
> + struct udevice *dev;
> +
> +Use ``ret`` as the return value:
> +
> +.. code-block:: C
> +
> + struct udevice *dev;
> + int ret;
> +
> + ret = uclass_first_device_err(UCLASS_ACPI_PMC, &dev);
> + if (ret)
> + return log_msg_ret("pmc", dev);
> +
> +Consider using log_ret() or log_msg_ret() to return a value (see above).
> +
> +Add a ``p`` suffix on return arguments:
> +
> +.. code-block:: C
> +
> + int dm_pci_find_class(uint find_class, int index, struct udevice
> **devp)
> + {
> + ...
> + *devp = dev;
> +
> + return 0;
> + }
> +
> +There are standard variable names that you should use in drivers:
> +
> +* ``struct xxx_priv`` and ``priv`` for dev_get_priv()
> +
> +* ``struct xxx_plat`` and ``plat`` for dev_get_platdata()
> +
> +For example:
> +
> +.. code-block:: C
> +
> + struct simple_bus_plat {
> + u32 base;
> + u32 size;
> + u32 target;
> + };
> +
> + /* Davinci MMC board definitions */
> + struct davinci_mmc_priv {
> + struct davinci_mmc_regs *reg_base; /* Register base address */
> + uint input_clk; /* Input clock to MMC controller */
> + struct gpio_desc cd_gpio; /* Card Detect GPIO */
> + struct gpio_desc wp_gpio; /* Write Protect GPIO */
> + };
> +
> + struct rcar_gpio_priv *priv = dev_get_priv(dev);
> +
> + struct pl01x_serial_platdata *plat = dev_get_platdata(dev);
> +
> +Other
> +-----
> +
> +Some minor things:
> +
> +* Put a blank line before the last ``return`` in a function unless it is
> the only line:
> +
> +.. code-block:: C
> +
> + struct udevice *pci_get_controller(struct udevice *dev)
> + {
> + while (device_is_on_pci_bus(dev))
> + dev = dev->parent;
> +
> + return dev;
> + }
> +
> +Tests
> +-----
> +
> +Please add tests when you add code. Please change or expand tests when
> you change code.
> +
> +Run the tests with::
> +
> + make check
> + make qcheck (skips some tests)
> +
> +Python tests are in test/py/tests - see the docs in test/py for info.
> +
> +Try to write your tests in C if you can. For example, tests to check a
> command
> +will be much faster (10-100x or more) if they can directly call
> run_command()
> +and ut_check_console_line() instead of using Python to send commands over
> a
> +pipe to U-Boot.
> +
> +Tests run all supported CI systems (gitlab, travis, azure) using scripts
> in the
> +root of the U-Boot tree.
> diff --git a/doc/develop/index.rst b/doc/develop/index.rst
> index fe3564a9fbf4..dde47994c71a 100644
> --- a/doc/develop/index.rst
> +++ b/doc/develop/index.rst
> @@ -3,6 +3,14 @@
> Develop U-Boot
> ==============
>
> +General
> +-------
> +
> +.. toctree::
> + :maxdepth: 1
> +
> + codingstyle
> +
> Implementation
> --------------
>
> --
> 2.25.1
>
>
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