i2c-howto.rst 2.1 KB

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  1. .. SPDX-License-Identifier: GPL-2.0+
  2. How to port an I2C driver to driver model
  3. =========================================
  4. Over half of the I2C drivers have been converted as at November 2016. These
  5. ones remain:
  6. * adi_i2c
  7. * davinci_i2c
  8. * fti2c010
  9. * ihs_i2c
  10. * kona_i2c
  11. * lpc32xx_i2c
  12. * pca9564_i2c
  13. * ppc4xx_i2c
  14. * rcar_i2c
  15. * sh_i2c
  16. * soft_i2c
  17. * zynq_i2c
  18. The deadline for this work is the end of June 2017. If no one steps
  19. forward to convert these, at some point there may come a patch to remove them!
  20. Here is a suggested approach for converting your I2C driver over to driver
  21. model. Please feel free to update this file with your ideas and suggestions.
  22. - #ifdef out all your own I2C driver code (#ifndef CONFIG_DM_I2C)
  23. - Define CONFIG_DM_I2C for your board, vendor or architecture
  24. - If the board does not already use driver model, you need CONFIG_DM also
  25. - Your board should then build, but will not work fully since there will be
  26. no I2C driver
  27. - Add the U_BOOT_DRIVER piece at the end (e.g. copy tegra_i2c.c for example)
  28. - Add a private struct for the driver data - avoid using static variables
  29. - Implement each of the driver methods, perhaps by calling your old methods
  30. - You may need to adjust the function parameters so that the old and new
  31. implementations can share most of the existing code
  32. - If you convert all existing users of the driver, remove the pre-driver-model
  33. code
  34. In terms of patches a conversion series typically has these patches:
  35. - clean up / prepare the driver for conversion
  36. - add driver model code
  37. - convert at least one existing board to use driver model serial
  38. - (if no boards remain that don't use driver model) remove the old code
  39. This may be a good time to move your board to use device tree also. Mostly
  40. this involves these steps:
  41. - define CONFIG_OF_CONTROL and CONFIG_OF_SEPARATE
  42. - add your device tree files to arch/<arch>/dts
  43. - update the Makefile there
  44. - Add stdout-path to your /chosen device tree node if it is not already there
  45. - build and get u-boot-dtb.bin so you can test it
  46. - Your drivers can now use device tree
  47. - For device tree in SPL, define CONFIG_SPL_OF_CONTROL