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dtoc: Update documentation to cover warnings in more detail

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When things go wrong it can be confusing to figure out what to change.
Add a few more details to the documentation.

Fix a 'make htmldocs' warning while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Walter Lozano <walter.lozano@collabora.com>
This commit is contained in:
Simon Glass 2021-07-04 12:19:50 -06:00
parent 43ba492670
commit e3dab846bd
1 changed files with 53 additions and 0 deletions
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53
doc/develop/driver-model/of-plat.rst
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@ -597,6 +597,59 @@ as a macro included in the driver definition::
Problems
--------
In some cases you will you see something like this::
WARNING: the driver rockchip_rk3188_grf was not found in the driver list
The driver list is a list of drivers, each with a name. The name is in the
U_BOOT_DRIVER() declaration, repeated twice, one in brackets and once as the
.name member. For example, in the following declaration the driver name is
`rockchip_rk3188_grf`::
U_BOOT_DRIVER(rockchip_rk3188_grf) = {
.name = "rockchip_rk3188_grf",
.id = UCLASS_SYSCON,
.of_match = rk3188_syscon_ids + 1,
.bind = rk3188_syscon_bind_of_plat,
};
The first name U_BOOT_DRIVER(xx) is used to create a linker symbol so that the
driver can be accessed at build-time without any overhead. The second one
(.name = "xx") is used at runtime when something wants to print out the driver
name.
The dtoc tool expects to be able to find a driver for each compatible string in
the devicetree. For example, if the devicetree has::
grf: grf@20008000 {
compatible = "rockchip,rk3188-grf", "syscon";
reg = <0x20008000 0x200>;
u-boot,dm-spl;
};
then dtoc looks at the first compatible string ("rockchip,rk3188-grf"),
converts that to a C identifier (rockchip_rk3188_grf) and then looks for that.
Various things can cause dtoc to fail to find the driver and it tries to
warn about these. For example:
rockchip_rk3188_uart: Missing .compatible in drivers/serial/serial_rockchip.c
: WARNING: the driver rockchip_rk3188_uart was not found in the driver list
Without a compatible string a driver cannot be used by dtoc, even if the
compatible string is not actually needed at runtime.
If the problem is simply that there are multiple compatible strings, the
DM_DRIVER_ALIAS() macro can be used to tell dtoc about this and avoid a problem.
Checks are also made to confirm that the referenced driver has a .compatible
member and a .id member. The first provides the array of compatible strings and
the second provides the uclass ID.
Caveats
-------