Improve some things in the documentation of OF_PLATDATA that I found while porting socfgpa_gen5 to it.
Signed-off-by: Simon Goldschmidt simon.k.r.goldschmidt@gmail.com ---
Changes in v2: - further fixes noted by Simon Glass - added info about missing node relations - moved the passage about phandles into section 'caveats'
doc/driver-model/of-plat.txt | 31 ++++++++++++++++++++----------- dts/Kconfig | 6 ++---- 2 files changed, 22 insertions(+), 15 deletions(-)
diff --git a/doc/driver-model/of-plat.txt b/doc/driver-model/of-plat.txt index 732bc34f06..0109ec56c3 100644 --- a/doc/driver-model/of-plat.txt +++ b/doc/driver-model/of-plat.txt @@ -64,17 +64,24 @@ strictly necessary. Notable problems include: normally also supports device tree it must use #ifdef to separate out this code, since the structures are only available in SPL.
+ - Correct relations between nodes are not implemented. This means that + parent/child relations (like bus device iteration) do not work yet. + Some phandles (those that are recognised as such) are converted into + a pointer to platform data. This pointer can potentially be used to + access the referenced device (by searching for the pointer value). + This feature is not yet implemented, however. +
How it works ------------
-The feature is enabled by CONFIG SPL_OF_PLATDATA. This is only available -in SPL and should be tested with: +The feature is enabled by CONFIG OF_PLATDATA. This is only available in +SPL/TPL and should be tested with:
- #if CONFIG_IS_ENABLED(SPL_OF_PLATDATA) + #if CONFIG_IS_ENABLED(OF_PLATDATA)
A new tool called 'dtoc' converts a device tree file either into a set of -struct declarations, one for each compatible node, or a set of +struct declarations, one for each compatible node, and a set of U_BOOT_DEVICE() declarations along with the actual platform data for each device. As an example, consider this MMC node:
@@ -156,6 +163,13 @@ This avoids the code overhead of converting the device tree data to platform data in the driver. The ofdata_to_platdata() method should therefore do nothing in such a driver.
+Note that for the platform data to be matched with a driver, the 'name' +property of the U_BOOT_DEVICE() declaration has to match a driver declared +via U_BOOT_DRIVER(). This effectively means that a U_BOOT_DRIVER() with a +'name' corresponding to the devicetree 'compatible' string (after converting +it to a valid name for C) is needed, so a dedicated driver is required for +each 'compatible' string. + Where a node has multiple compatible strings, a #define is used to make them equivalent, e.g.:
@@ -165,8 +179,8 @@ equivalent, e.g.: Converting of-platdata to a useful form ---------------------------------------
-Of course it would be possible use the of-platdata directly in your driver -whenever configuration information is required. However this meands that the +Of course it would be possible to use the of-platdata directly in your driver +whenever configuration information is required. However this means that the driver will not be able to support device tree, since the of-platdata structure is not available when device tree is used. It would make no sense to use this structure if device tree were available, since the structure has @@ -282,11 +296,6 @@ prevents them being used inadvertently. All usage must be bracketed with The dt-platdata.c file contains the device declarations and is is built in spl/dt-platdata.c.
-Some phandles (thsoe that are recognised as such) are converted into -points to platform data. This pointer can potentially be used to access the -referenced device (by searching for the pointer value). This feature is not -yet implemented, however. - The beginnings of a libfdt Python module are provided. So far this only implements a subset of the features.
diff --git a/dts/Kconfig b/dts/Kconfig index 8917f42444..3e85914d11 100644 --- a/dts/Kconfig +++ b/dts/Kconfig @@ -265,8 +265,7 @@ config SPL_OF_PLATDATA
This option works by generating C structure declarations for each compatible string, then adding platform data and U_BOOT_DEVICE - declarations for each node. See README.platdata for more - information. + declarations for each node. See of-plat.txt for more information.
config TPL_OF_PLATDATA bool "Generate platform data for use in TPL" @@ -287,8 +286,7 @@ config TPL_OF_PLATDATA
This option works by generating C structure declarations for each compatible string, then adding platform data and U_BOOT_DEVICE - declarations for each node. See README.platdata for more - information. + declarations for each node. See of-plat.txt for more information.
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