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clk: Document of_parse_clkspec() some more 

The return value of of_parse_clkspec() is peculiar. If the function is
called with a NULL argument for 'name' it will return -ENOENT, but if
it's called with a non-NULL argument for 'name' it will return -EINVAL.
This peculiarity is documented by commit 5c56dfe63b ("clk: Add comment
about __of_clk_get_by_name() error values").

Let's further document this function so that it's clear what the return
value is and how to use the arguments to parse clk specifiers.

Cc: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lkml.kernel.org/r/20190826212042.48642-1-sboyd@kernel.org
Reviewed-by: Phil Edworthy <phil.edworthy@renesas.com>
This commit is contained in:
Stephen Boyd 2019-08-26 14:20:42 -07:00
parent ef13e55c27
commit 226fd70209
1 changed files with 37 additions and 6 deletions
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43
drivers/clk/clk.c
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@ -4316,12 +4316,43 @@ void devm_of_clk_del_provider(struct device *dev)
}
EXPORT_SYMBOL(devm_of_clk_del_provider);
/*
* Beware the return values when np is valid, but no clock provider is found.
* If name == NULL, the function returns -ENOENT.
* If name != NULL, the function returns -EINVAL. This is because
* of_parse_phandle_with_args() is called even if of_property_match_string()
* returns an error.
/**
* of_parse_clkspec() - Parse a DT clock specifier for a given device node
* @np: device node to parse clock specifier from
* @index: index of phandle to parse clock out of. If index < 0, @name is used
* @name: clock name to find and parse. If name is NULL, the index is used
* @out_args: Result of parsing the clock specifier
*
* Parses a device node's "clocks" and "clock-names" properties to find the
* phandle and cells for the index or name that is desired. The resulting clock
* specifier is placed into @out_args, or an errno is returned when there's a
* parsing error. The @index argument is ignored if @name is non-NULL.
*
* Example:
*
* phandle1: clock-controller@1 {
* #clock-cells = <2>;
* }
*
* phandle2: clock-controller@2 {
* #clock-cells = <1>;
* }
*
* clock-consumer@3 {
* clocks = <&phandle1 1 2 &phandle2 3>;
* clock-names = "name1", "name2";
* }
*
* To get a device_node for `clock-controller@2' node you may call this
* function a few different ways:
*
* of_parse_clkspec(clock-consumer@3, -1, "name2", &args);
* of_parse_clkspec(clock-consumer@3, 1, NULL, &args);
* of_parse_clkspec(clock-consumer@3, 1, "name2", &args);
*
* Return: 0 upon successfully parsing the clock specifier. Otherwise, -ENOENT
* if @name is NULL or -EINVAL if @name is non-NULL and it can't be found in
* the "clock-names" property of @np.
*/
static int of_parse_clkspec(const struct device_node *np, int index,
const char *name, struct of_phandle_args *out_args)