How to port a serial driver to driver model

Almost all of the serial drivers have been converted as at January 2016. These ones remain:

  • serial_bfin.c

  • serial_pxa.c

The deadline for this work was the end of January 2016. 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 serial driver over to driver model. Please feel free to update this file with your ideas and suggestions.

  • #ifdef out all your own serial driver code (#ifndef CONFIG_DM_SERIAL)

  • Define CONFIG_DM_SERIAL 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 boot since there will be no serial driver

  • Add the U_BOOT_DRIVER piece at the end (e.g. copy serial_s5p.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