[PATCH v2] clk: Document of_parse_clkspec() some more

[PATCH v2] clk: Document of_parse_clkspec() some more

[Stephen Boyd]

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>
---
 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 c0990703ce54..5c6585eb35d4 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)
-- 
Sent by a computer through tubes

RE: [PATCH v2] clk: Document of_parse_clkspec() some more

[Phil Edworthy]

Hi Stephen,

On 26 August 2019 22:21 Stephen Boyd wrote:
> 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>

Thanks, this is much better than my comment!

Reviewed-by: Phil Edworthy <phil.edworthy@renesas.com>

> ---
>  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 c0990703ce54..5c6585eb35d4 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)
> --
> Sent by a computer through tubes

Re: [PATCH v2] clk: Document of_parse_clkspec() some more

[Stephen Boyd]

Quoting Stephen Boyd (2019-08-26 14:20:42)
> 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>
> ---

Applied to clk-next