doc/driver-model/i2c-howto.txt

   1 How to port a serial driver to driver model
   2 ===========================================
   3
   4 Over half of the I2C drivers have been converted as at November 2016. These
   5 ones remain:
   6
   7    adi_i2c
   8    davinci_i2c
   9    fti2c010
  10    ihs_i2c
  11    kona_i2c
  12    lpc32xx_i2c
  13    pca9564_i2c
  14    ppc4xx_i2c
  15    rcar_i2c
  16    sh_i2c
  17    sh_sh7734_i2c
  18    soft_i2c
  19    tsi108_i2c
  20    zynq_i2c
  21
  22 The deadline for this work is the end of June 2017. If no one steps
  23 forward to convert these, at some point there may come a patch to remove them!
  24
  25 Here is a suggested approach for converting your I2C driver over to driver
  26 model. Please feel free to update this file with your ideas and suggestions.
  27
  28 - #ifdef out all your own I2C driver code (#ifndef CONFIG_DM_I2C)
  29 - Define CONFIG_DM_I2C for your board, vendor or architecture
  30 - If the board does not already use driver model, you need CONFIG_DM also
  31 - Your board should then build, but will not work fully since there will be
  32     no I2C driver
  33 - Add the U_BOOT_DRIVER piece at the end (e.g. copy tegra_i2c.c for example)
  34 - Add a private struct for the driver data - avoid using static variables
  35 - Implement each of the driver methods, perhaps by calling your old methods
  36 - You may need to adjust the function parameters so that the old and new
  37     implementations can share most of the existing code
  38 - If you convert all existing users of the driver, remove the pre-driver-model
  39     code
  40
  41 In terms of patches a conversion series typically has these patches:
  42 - clean up / prepare the driver for conversion
  43 - add driver model code
  44 - convert at least one existing board to use driver model serial
  45 - (if no boards remain that don't use driver model) remove the old code
  46
  47 This may be a good time to move your board to use device tree also. Mostly
  48 this involves these steps:
  49
  50 - define CONFIG_OF_CONTROL and CONFIG_OF_SEPARATE
  51 - add your device tree files to arch/<arch>/dts
  52 - update the Makefile there
  53 - Add stdout-path to your /chosen device tree node if it is not already there
  54 - build and get u-boot-dtb.bin so you can test it
  55 - Your drivers can now use device tree
  56 - For device tree in SPL, define CONFIG_SPL_OF_CONTROL