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| freebsdarmboards [2008/11/30 21:35] – WarnerLosh | freebsdarmboards [2018/03/23 14:34] (current) – stale page: last update by original author 2008-11-30 21:35:36. MarkLinimon |
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| ==== Flattened Device Tree ==== | ==== Flattened Device Tree ==== |
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| There's also a desire to have some way to specify most of the hardware via a config file that's interpreted at run time. The flattened device tree that Linux's %%PowerPC%% port uses has a number of very desirable traits. First, uboot supports passing in a compiled version of this file into the tree for boards that don't support full OpenFirmware. Second, it represents a number of overlaid relationships between different nodes in a device tree. Third, most board vendors that support linux have started producing these files. Our barrier to entry would also be lowered if we could use them. | There's also a desire to have some way to specify most of the hardware via a config file that's interpreted at run time. The flattened device tree that Linux's %%PowerPC%% port uses has a number of very desirable traits. First, uboot supports passing in a compiled version of this file into the tree for boards that don't support full %%OpenFirmware%%. Second, it represents a number of overlaid relationships between different nodes in a device tree. Third, most board vendors that support linux have started producing these files. Our barrier to entry would also be lowered if we could use them. |
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| The interesting thing about the FDTs is that they encode non-heirarchical relationships between devices, as are often found when GPIOs are used for interrupts, when interrupt controllers are wired externally to the bus hierarchy, etc. They also can encode things like the wiring of the different elements of a sound/video subsystem, which might have different relationships still than the bus hierarchy. | The interesting thing about the FDTs is that they encode non-heirarchical relationships between devices, as are often found when GPIOs are used for interrupts, when interrupt controllers are wired externally to the bus hierarchy, etc. They also can encode things like the wiring of the different elements of a sound/video subsystem, which might have different relationships still than the bus hierarchy. |
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| There's some suggestions that there be a separate "boards" directory. I'm not sure that I like it. | There's some suggestions that there be a separate "boards" directory. I'm not sure that I like it. |
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