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.goldschm...@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.
endmenu
--
2.17.1
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