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