mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-05 02:51:00 +00:00
5ce319133b
These docs are useful for developers, not users. Move them under that section. Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de> Signed-off-by: Simon Glass <sjg@chromium.org>
56 lines
2.1 KiB
ReStructuredText
56 lines
2.1 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
|
|
|
|
How to port an I2C driver to driver model
|
|
=========================================
|
|
|
|
Over half of the I2C drivers have been converted as at November 2016. These
|
|
ones remain:
|
|
|
|
* adi_i2c
|
|
* davinci_i2c
|
|
* fti2c010
|
|
* ihs_i2c
|
|
* kona_i2c
|
|
* lpc32xx_i2c
|
|
* pca9564_i2c
|
|
* ppc4xx_i2c
|
|
* rcar_i2c
|
|
* sh_i2c
|
|
* soft_i2c
|
|
* zynq_i2c
|
|
|
|
The deadline for this work is the end of June 2017. If no one steps
|
|
forward to convert these, at some point there may come a patch to remove them!
|
|
|
|
Here is a suggested approach for converting your I2C driver over to driver
|
|
model. Please feel free to update this file with your ideas and suggestions.
|
|
|
|
- #ifdef out all your own I2C driver code (#if !CONFIG_IS_ENABLED(DM_I2C))
|
|
- Define CONFIG_DM_I2C for your board, vendor or architecture
|
|
- If the board does not already use driver model, you need CONFIG_DM also
|
|
- Your board should then build, but will not work fully since there will be
|
|
no I2C driver
|
|
- Add the U_BOOT_DRIVER piece at the end (e.g. copy tegra_i2c.c for example)
|
|
- Add a private struct for the driver data - avoid using static variables
|
|
- Implement each of the driver methods, perhaps by calling your old methods
|
|
- You may need to adjust the function parameters so that the old and new
|
|
implementations can share most of the existing code
|
|
- If you convert all existing users of the driver, remove the pre-driver-model
|
|
code
|
|
|
|
In terms of patches a conversion series typically has these patches:
|
|
- clean up / prepare the driver for conversion
|
|
- add driver model code
|
|
- convert at least one existing board to use driver model serial
|
|
- (if no boards remain that don't use driver model) remove the old code
|
|
|
|
This may be a good time to move your board to use device tree also. Mostly
|
|
this involves these steps:
|
|
|
|
- define CONFIG_OF_CONTROL and CONFIG_OF_SEPARATE
|
|
- add your device tree files to arch/<arch>/dts
|
|
- update the Makefile there
|
|
- Add stdout-path to your /chosen device tree node if it is not already there
|
|
- build and get u-boot-dtb.bin so you can test it
|
|
- Your drivers can now use device tree
|
|
- For device tree in SPL, define CONFIG_SPL_OF_CONTROL
|