Re: [PATCH v2] clk: let of_clk_get_parent_name() fail for invalid clock-indices

From: Masahiro Yamada
Date: Mon Nov 30 2015 - 21:48:31 EST


Hi Stephen,


2015-12-01 9:58 GMT+09:00 Stephen Boyd <sboyd@xxxxxxxxxxxxxx>:
> On 11/30, Masahiro Yamada wrote:
>> Currently, of_clk_get_parent_name() returns a wrong parent clock name
>> when "clock-indices" property exists and the target index is not
>> found in the property. In this case, NULL should be returned.
>>
>> For example,
>>
>> oscillator {
>> compatible = "myclocktype";
>> #clock-cells = <1>;
>> clock-indices = <1>, <3>;
>> clock-output-names = "clka", "clkb";
>> };
>>
>> consumer {
>> compatible = "myclockconsumer";
>> clocks = <&oscillator 0>, <&oscillator 1>;
>> };
>>
>> Currently, of_clk_get_parent_name(consumer_np, 0) returns "clka"
>> (and of_clk_get_parent_name(consumer_np, 1) also returns "clka",
>> this is correct). Because the "clock-indices" in the clock parent
>> does not contain <0>, of_clk_get_parent_name(consumer_np, 0) should
>> return NULL.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
>
> Here's the proposed alternative, if you agree I will merge it
> with the above commit text and attribution to you.
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index a66efc9d8bfc..f54583a9835a 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3079,6 +3079,9 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
> }
> count++;
> }
> + /* We went off the end of 'clock-indices' without finding it */
> + if (!vp && count)
> + return NULL;
>
> if (of_property_read_string_index(clkspec.np, "clock-output-names",
> index,
>

No, again.
The existence of "clock-indices" should be checked
in order to omit the zero-length "clock-indices".


OK, let me guess the next alternative from you.


> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3079,6 +3079,9 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
> }
> count++;
> }
> + /* We went off the end of 'clock-indices' without finding it */
> + if (prop && !vp)
> + return NULL;
>
> if (of_property_read_string_index(clkspec.np, "clock-output-names",
> index,
>

This works, but clumsy things are:

[1] If the "clock-indices" is missing, we can know it
before looping around the of_property_for_each_u32().
Checking the "prop" after the loop seems odd.

[2] "prop" and "vp" seem to be temporary storage that we should not
know what they exactly are, like the auxiliary pointer in
list_for_each_safe().


Why do you insist on of_property_for_each_u32()?
It no longer fits in here.


--
Best Regards
Masahiro Yamada
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