doc: Migrate CodingStyle wiki page to Sphinx

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@gmx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>

2 files changed, 266 insertions, 0 deletions

diff --git a/doc/develop/codingstyle.rst b/doc/develop/codingstyle.rst
new file mode 100644
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+.. 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
+
+    * The exception here is Python which requires 4 spaces instead.
+
+  * All source files need to be in "Unix" and not "DOS" or "Windows" formatted,
+    with respect to line ends.
+
+  * 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 the check_member() macro 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 fe3564a9fbf..dde47994c71 100644
--- a/doc/develop/index.rst
+++ b/doc/develop/index.rst
@@ -3,6 +3,14 @@
 Develop U-Boot
 ==============
 
+General
+-------
+
+.. toctree::
+   :maxdepth: 1
+
+   codingstyle
+
 Implementation
 --------------