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| -rw-r--r-- | doc/driver-model/i2c-howto.txt | 56 |
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diff --git a/doc/driver-model/i2c-howto.txt b/doc/driver-model/i2c-howto.txt new file mode 100644 index 0000000000..605d3ef7ad --- /dev/null +++ b/doc/driver-model/i2c-howto.txt @@ -0,0 +1,56 @@ +How to port a serial 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 + sh_sh7734_i2c + soft_i2c + tsi108_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 (#ifndef CONFIG_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 |