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authorStephen Boyd <sboyd@kernel.org>2019-08-26 14:20:42 -0700
committerStephen Boyd <sboyd@kernel.org>2019-09-05 11:51:31 -0700
commit226fd70209451428c563977f5ce022a41d077110 (patch)
tree68f7733b1d36a99452588d8af3174af617a6d564 /drivers/clk/clk.c
parentef13e55c27e128b6d84aa939dcc565b1d2ee7724 (diff)
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 <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>
Diffstat (limited to 'drivers/clk/clk.c')
-rw-r--r--drivers/clk/clk.c43
1 files changed, 37 insertions, 6 deletions
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index bea50eee9e8c..4649e036eed2 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)