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Diffstat (limited to 'doc/driver-model/README.txt')
| -rw-r--r-- | doc/driver-model/README.txt | 17 |
1 files changed, 15 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"; |