On Sun, May 20, 2018 at 01:57:00PM -0600, Simon Glass wrote:
> This is missing at present and the fdtget tool is no-longer trivial. Add
> a little bit of information.
>
> This might be useful for distributions which want to provide a man page.
>
> Signed-off-by: Simon Glass <sjg@xxxxxxxxxxxx>
I like the idea of adding documentation.
However, I still need to think a bit about the phandle decoding patch.
Could you re-order these - documenting fdtget/fdtput as they stand
before the phandle decoding and moving the documentation update to the
next draft of the phandle decoding patch. Then I can apply the
documentation patch while considering the rest.
> ---
>
> Documentation/manual.txt | 67 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 67 insertions(+)
>
> diff --git a/Documentation/manual.txt b/Documentation/manual.txt
> index 72403ac..dd4d888 100644
> --- a/Documentation/manual.txt
> +++ b/Documentation/manual.txt
> @@ -693,3 +693,70 @@ Where options are:
> -i, --input Input base DT blob
> -o, --output Output DT blob
> -v, --verbose Verbose message output
> +
> +4 ) fdtget -- Read properties from device tree
> +
> +This command can be used to obtain individual values from the device tree in a
> +nicely formatted way. You can specify multiple nodes to display (when using -p)
> +or multiple node/property pairs (when not using -p). For the latter, each
> +property is displayed on its own line, with a space between each cell within
> +the property.
> +
> +The syntax of the fdtget command is:
> +
> + fdtget <options> <dt file> [<node> <property>]...
> + fdtget -p <options> <dt file> [<node> ]...
> +
> +where options are:
> +
> + <type> s=string, i=int, u=unsigned, x=hex
> + Optional modifier prefix:
> + hh or b=byte, h=2 byte, l=4 byte (default)
> +
> + -t, --type <arg> Type of data
> + -p, --properties List properties for each node
> + -l, --list List subnodes for each node
> + -d, --default <arg> Default value to display when the property is missing
> + -P, --decode-phandles Decode phandles to show the target node and (with -c) args (this only supports some common cases)
> + -c, --cells <arg> Cells property in phandle target (e.g. 'gpio' for '#gpio-cells')
> + -h, --help Print this help and exit
> + -V, --version Print version and exit
> +
> +If -t is not provided, fdtget will try to figure out the type, trying to detect
> +strings, string lists and the size of each value in the property. This is
> +similar to how fdtdump works, and uses the same heuristics.
> +
> +The phandle feature (-P) provides a way to decode and display phandles. It
> +should only be used on properties which use a particular (fairly common)
> +phandle format:
> +
> + <phandle> <n cells of stuff> <phandle> <m cells of stuff>
> +
> +For example, consider this device-tree fragment:
> +
> + pinctrl {
> + gpio0: gpio0@ff750000 {
> + #gpio-cells = <2>;
> + };
> + };
> +
> + gpio-keys {
> + button@0 {
> + gpios = <&gpio0 5 GPIO_ACTIVE_LOW>;
> + };
> + };
> +
> +
> +Normally fdtget weil display the 'gpios' property like this:
> +
> + $ fdtget firefly-rk3288/u-boot.dtb /gpio-keys/button@0 gpios
> + 112 5 1
> +
> +but with -P was can request that the phandle be decoded and shown as a part:
> +
> + $ fdtget firefly-rk3288/u-boot.dtb -P -c gpio /gpio-keys/button@0 gpios
> + /pinctrl/gpio0@ff750000 5 1
> +
> +Note that '-c gpio' is needed to tell fdtget to use the #gpio-cells property
> +to figure out the number of arguments for each phandle. Without that it cannot
> +display the arguments correctly.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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