From 226fd70209451428c563977f5ce022a41d077110 Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Mon, 26 Aug 2019 14:20:42 -0700 Subject: [PATCH] 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 5c56dfe63b6e ("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 Signed-off-by: Stephen Boyd Link: https://lkml.kernel.org/r/20190826212042.48642-1-sboyd@kernel.org Reviewed-by: Phil Edworthy --- drivers/clk/clk.c | 43 +++++++++++++++++++++++++++++++++++++------ 1 file changed, 37 insertions(+), 6 deletions(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index bea50ee..4649e03 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -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) -- 2.7.4