diff options
| -rw-r--r-- | doc/driver-model/README.txt | 17 | ||||
| -rw-r--r-- | include/dm/platdata.h | 9 |
2 files changed, 24 insertions, 2 deletions
diff --git a/doc/driver-model/README.txt b/doc/driver-model/README.txt index f0276b1b46..b891e8459d 100644 --- a/doc/driver-model/README.txt +++ b/doc/driver-model/README.txt @@ -301,6 +301,15 @@ device tree) and probe. Platform Data ------------- +*** Note: platform data is the old way of doing things. It is +*** basically a C structure which is passed to drivers to tell them about +*** platform-specific settings like the address of its registers, bus +*** speed, etc. Device tree is now the preferred way of handling this. +*** Unless you have a good reason not to use device tree (the main one +*** being you need serial support in SPL and don't have enough SRAM for +*** the cut-down device tree and libfdt libraries) you should stay away +*** from platform data. + Platform data is like Linux platform data, if you are familiar with that. It provides the board-specific information to start up a device. @@ -366,8 +375,12 @@ Device Tree ----------- While platdata is useful, a more flexible way of providing device data is -by using device tree. With device tree we replace the above code with the -following device tree fragment: +by using device tree. In U-Boot you should use this where possible. Avoid +sending patches which make use of the U_BOOT_DEVICE() macro unless strictly +necessary. + +With device tree we replace the above code with the following device tree +fragment: red-square { compatible = "demo-shape"; diff --git a/include/dm/platdata.h b/include/dm/platdata.h index fbc8a6b3ad..6f4f00140e 100644 --- a/include/dm/platdata.h +++ b/include/dm/platdata.h @@ -16,6 +16,10 @@ /** * struct driver_info - Information required to instantiate a device * + * NOTE: Avoid using this except in extreme circumstances, where device tree + * is not feasible (e.g. serial driver in SPL where <8KB of SRAM is + * available). U-Boot's driver model uses device tree for configuration. + * * @name: Driver name * @platdata: Driver-specific platform data */ @@ -24,6 +28,11 @@ struct driver_info { const void *platdata; }; +/** + * NOTE: Avoid using these except in extreme circumstances, where device tree + * is not feasible (e.g. serial driver in SPL where <8KB of SRAM is + * available). U-Boot's driver model uses device tree for configuration. + */ #define U_BOOT_DEVICE(__name) \ ll_entry_declare(struct driver_info, __name, driver_info) |