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:

  • 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