Re: [PATCH RFC 4/5] clk: add placeholder for clock internal data

[Stephen Boyd <sboyd@kernel.org>]

Quoting Jerome Brunet (2019-08-29 00:20:38)
> On Wed 28 Aug 2019 at 15:15, Stephen Boyd <sboyd@kernel.org> wrote:
> 
> > Quoting Jerome Brunet (2019-08-28 03:20:11)
> >> Add placeholder in clock core to save per clock data.
> >> Such placeholder could use for clock doing memory allocation in .init().
> >> It may also be useful for the save/restore_context() callbacks.
> >> 
> >> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
> >> ---
> >>  drivers/clk/clk.c            | 13 +++++++++++++
> >>  include/linux/clk-provider.h |  2 ++
> >>  2 files changed, 15 insertions(+)
> >> 
> >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> >> index c703aa35ca37..aa77a2a98ea4 100644
> >> --- a/drivers/clk/clk.c
> >> +++ b/drivers/clk/clk.c
> >> @@ -83,6 +83,7 @@ struct clk_core {
> >>         struct hlist_node       debug_node;
> >>  #endif
> >>         struct kref             ref;
> >> +       void                    *priv;
> >
> > Why? We have container structures around clk_hw that can be used to
> > store data and clk_ops that should know to deref said clk_hw pointer in
> > some way to access that data.
> 
> This simple addition give a placeholder to each clock instance that is
> hosted under the clock core so we know it can only be accesed from this
> particular instance. Seems like a better fit for runtime data, such as
> saved context.
> 
> It gives a way to avoid mixing the clock description and its runtime
> data. In the end, It would be nice if the clock description part could
> be made const.
> 
> This is a (fairly usual) way to do it 

Maybe you can provide an example or usage? Is that the last patch in
this series? I still don't quite understand why we need this.

I imagine that if you wanted to have a const description part you could
have a container structure around the clk_hw struct

	struct my_clk_foo {
		const struct clk_description *desc;
		<runtime modifiable members>;
		struct clk_hw hw;
	};

Did I miss something?