Re: [PATCH v5 2/8] clk: Warn if clk_init_data is not zero initialized

[Stephen Boyd <sboyd@kernel.org>]

Quoting Manivannan Sadhasivam (2019-09-16 09:14:41)
> The new implementation for determining parent map uses multiple ways
> to pass parent info. The order in which it gets processed depends on
> the first available member. Hence, it is necessary to zero init the
> clk_init_data struct so that the expected member gets processed correctly.
> So, add a warning if multiple clk_init_data members are available during
> clk registration.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
>  drivers/clk/clk.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index c0990703ce54..7d6d6984c979 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3497,6 +3497,14 @@ static int clk_core_populate_parent_map(struct clk_core *core)
>         if (!num_parents)
>                 return 0;
>  
> +       /*
> +        * Check for non-zero initialized clk_init_data struct. This is
> +        * required because, we only require one of the (parent_names/
> +        * parent_data/parent_hws) to be set at a time. Otherwise, the
> +        * current code would use first available member.
> +        */
> +       WARN_ON((parent_names && parent_data) || (parent_names && parent_hws));
> +

This will warn for many drivers because they set clk_init_data on the
stack and assign parent_names but let junk from the stack be assigned to
parent_data. The code uses parent_names first and then looks for
parent_data or parent_hws because of this fact of life that we've never
required clk_init_data to be initialized to all zero.

>         /*
>          * Avoid unnecessary string look-ups of clk_core's possible parents by
>          * having a cache of names/clk_hw pointers to clk_core pointers.