diff options
Diffstat (limited to 'doc/develop')
| -rw-r--r-- | doc/develop/codingstyle.rst | 81 | ||||
| -rw-r--r-- | doc/develop/falcon.rst | 84 |
2 files changed, 86 insertions, 79 deletions
diff --git a/doc/develop/codingstyle.rst b/doc/develop/codingstyle.rst index 8ed6babe455..013bfebf7e4 100644 --- a/doc/develop/codingstyle.rst +++ b/doc/develop/codingstyle.rst @@ -12,8 +12,9 @@ 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>`_. + coding style <https://www.kernel.org/doc/html/latest/process/coding-style.html>`_. + U-Boot includes a `.clang-format` configuration file that can be used to + automatically format code according to these standards. * 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 @@ -73,6 +74,82 @@ The following rules apply: issues are resolved *before* posting on the mailing list. For more information, read :doc:`checkpatch`. +Code Formatting with clang-format +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +U-Boot provides a `.clang-format` configuration file that was copied directly +from the Linux kernel without any modifications, ensuring complete compatibility +with kernel coding standards. Here are common ways to use clang-format: + +**Basic usage for single files:** + +.. code-block:: bash + + clang-format -style=file -i <file> + +**Format multiple files:** + +.. code-block:: bash + + find . -name '*.c' -o -name '*.h' | xargs clang-format -style=file -i + +**Integration with git (format only staged changes):** + +.. code-block:: bash + + git clang-format + +**Editor integration examples:** + +* **Vim/Neovim:** Install vim-clang-format plugin +* **Emacs:** Use clang-format.el +* **VSCode:** Install "Clang-Format" extension +* **Most IDEs:** Have built-in or plugin support for clang-format + +The `.clang-format` file in the repository root ensures consistent formatting +across the entire codebase and aligns with Linux kernel coding standards. + +**Disabling clang-format for specific code blocks:** + +In some cases, you may want to disable automatic formatting for specific code +sections, such as carefully formatted tables, assembly code, or imported code +from other projects. Use the following comments to control formatting: + +.. code-block:: c + + // clang-format off + static const struct register_config regs[] = { + { 0x1000, 0x12345678 }, // Base address register + { 0x1004, 0xabcdef00 }, // Control register + { 0x1008, 0x00000001 }, // Status register + }; + // clang-format on + +**Controversial aspects of coding style enforcement:** + +Coding style enforcement can be controversial, and it's difficult to have one +configuration that satisfies everyone's personal preferences. The goal of using +clang-format is consistency across the codebase rather than accommodating +individual preferences. While some developers may disagree with specific +formatting choices, maintaining a uniform style throughout the project makes +code more readable and maintainable for the entire development community. + +**Best practices for formatting:** + +When using clang-format to format code, consider these best practices: + +* **Format only changed blocks:** It's preferred to format only the blocks of + code that have been modified rather than entire files. This keeps diffs + focused on actual changes and makes code reviews easier. + +* **Separate formatting commits:** If you need to format entire files, create + a separate commit containing only formatting changes. This allows reviewers + to easily distinguish between functional changes and pure formatting updates. + +* **Use git clang-format:** The ``git clang-format`` command is particularly + useful as it formats only the lines that have been modified in your current + changes, avoiding unnecessary formatting of unchanged code. + * 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 diff --git a/doc/develop/falcon.rst b/doc/develop/falcon.rst index 244b4ccb5c2..5689d5b93a7 100644 --- a/doc/develop/falcon.rst +++ b/doc/develop/falcon.rst @@ -22,7 +22,7 @@ copies U-Boot image into the memory. The Falcon Mode extends this way allowing to start the Linux kernel directly from SPL. A new command is added to U-Boot to prepare the parameters that SPL -must pass to the kernel, using ATAGS or Device Tree. +must pass to the kernel using a Device Tree. In normal mode, these parameters are generated each time before loading the kernel, passing to Linux the address in memory where @@ -117,10 +117,7 @@ spl - SPL configuration Usage:: - spl export <img=atags|fdt> [kernel_addr] [initrd_addr] [fdt_addr ] - -img - "atags" or "fdt" + spl export fdt [kernel_addr] [initrd_addr] [fdt_addr ] kernel_addr kernel is loaded as part of the boot process, but it is not started. @@ -134,11 +131,11 @@ fdt_addr in case of fdt, the address of the device tree. The *spl export* command does not write to a storage media. The user is -responsible to transfer the gathered information (assembled ATAGS list -or prepared FDT) from temporary storage in RAM into persistent storage -after each run of *spl export*. Unfortunately the position of temporary -storage can not be predicted nor provided at command line, it depends -highly on your system setup and your provided data (ATAGS or FDT). +responsible to transfer the gathered information (prepared FDT) from temporary +storage in RAM into persistent storage after each run of *spl export*. +Unfortunately the position of temporary storage can not be predicted nor +provided at command line, it depends highly on your system setup and your +provided device tree. However at the end of an successful *spl export* run it will print the RAM address of temporary storage. The RAM address of FDT will also be set in the environment variable *fdtargsaddr*, the new length of the @@ -152,73 +149,6 @@ to the pre-defined address in persistent storage The following example shows how to prepare the data for Falcon Mode on twister board with ATAGS BLOB. -The *spl export* command is prepared to work with ATAGS and FDT. However, -using FDT is at the moment untested. The ppc port (see a3m071 example -later) prepares the fdt blob with the fdt command instead. - - -Usage on the twister board --------------------------- - -Using mtd names with the following (default) configuration -for mtdparts:: - - device nand0 <omap2-nand.0>, # parts = 9 - #: name size offset mask_flags - 0: MLO 0x00080000 0x00000000 0 - 1: u-boot 0x00100000 0x00080000 0 - 2: env1 0x00040000 0x00180000 0 - 3: env2 0x00040000 0x001c0000 0 - 4: kernel 0x00600000 0x00200000 0 - 5: bootparms 0x00040000 0x00800000 0 - 6: splashimg 0x00200000 0x00840000 0 - 7: mini 0x02800000 0x00a40000 0 - 8: rootfs 0x1cdc0000 0x03240000 0 - -:: - - twister => nand read 82000000 kernel - - NAND read: device 0 offset 0x200000, size 0x600000 - 6291456 bytes read: OK - -Now the kernel is in RAM at address 0x82000000:: - - twister => spl export atags 0x82000000 - ## Booting kernel from Legacy Image at 82000000 ... - Image Name: Linux-3.5.0-rc4-14089-gda0b7f4 - Image Type: ARM Linux Kernel Image (uncompressed) - Data Size: 3654808 Bytes = 3.5 MiB - Load Address: 80008000 - Entry Point: 80008000 - Verifying Checksum ... OK - Loading Kernel Image ... OK - OK - cmdline subcommand not supported - bdt subcommand not supported - Argument image is now in RAM at: 0x80000100 - -The result can be checked at address 0x80000100:: - - twister => md 0x80000100 - 80000100: 00000005 54410001 00000000 00000000 ......AT........ - 80000110: 00000000 00000067 54410009 746f6f72 ....g.....ATroot - 80000120: 65642f3d 666e2f76 77722073 73666e20 =/dev/nfs rw nfs - -The parameters generated with this step can be saved into NAND at the offset -0x800000 (value for twister for CONFIG_CMD_SPL_NAND_OFS):: - - nand erase.part bootparms - nand write 0x80000100 bootparms 0x4000 - -Now the parameters are stored into the NAND flash at the address -CONFIG_CMD_SPL_NAND_OFS (=0x800000). - -Next time, the board can be started into Falcon Mode moving the -setting the GPIO (on twister GPIO 55 is used) to kernel mode. - -The kernel is loaded directly by the SPL without passing through U-Boot. - Example with FDT: a3m071 board ------------------------------ |