Hi Weiyi,

On 26/05/2020 04:43, Weiyi Lu wrote:

On Mon, 2020-05-25 at 11:08 +0200, Matthias Brugger wrote:

quoted

On 25/05/2020 08:41, Weiyi Lu wrote:

quoted

It'd be dangerous when struct clk_core have new memebers.
Add the missing initial value to clk_init_data.

Sorry I don't really understand this commit message, can please explain.
In any case if this is a problem, then we probably we should fix it for all drivers.
Apart from drivers/clk/mediatek/clk-cpumux.c

Actually, we were looking into an android kernel patch "ANDROID: GKI:
clk: Add support for voltage voting" [1]

In this patch, there adds a new member struct clk_vdd_class	*vdd_class;
in struct clk_init_data and struct clk_core

And then in clk_register(...)
core->vdd_class = hw->init->vdd_class;

In many clock APIs, it will check the core->vdd_class to select the
correct control flow.
So, if we don't assign an initial value to clk_init_data of mtk_mux
clock type, something might go wrong. And assigning an initial value
might be the easiest and good way to avoid such problem if any new clock
support added in the future.

Thanks for your explanation. You mean that as clk_init_data is on the stack it
can have random values, and would lead to the fact that vdd_class is interpreted
as allocated although it should be NULL.

Sounds reasonable to me. You might want to resend with a better commit message.
Feel free to add my

Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>

Regards,
Matthias

[1] https://android-review.googlesource.com/c/kernel/common/+/1278046

quoted

It's a widely used pattern:
$ git grep "struct clk_init_data init;"| wc -l
235

Regards,
Matthias

quoted

Fixes: a3ae549917f1 ("clk: mediatek: Add new clkmux register API")
Cc: <redacted>
Signed-off-by: Weiyi Lu <redacted>
---
 drivers/clk/mediatek/clk-mux.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/mediatek/clk-mux.c b/drivers/clk/mediatek/clk-mux.c
index 76f9cd0..14e127e 100644
--- a/drivers/clk/mediatek/clk-mux.c
+++ b/drivers/clk/mediatek/clk-mux.c

@@ -160,7 +160,7 @@ struct clk *mtk_clk_register_mux(const struct mtk_mux *mux,
 				 spinlock_t *lock)
 {
 	struct mtk_clk_mux *clk_mux;
-	struct clk_init_data init;
+	struct clk_init_data init = {};
 	struct clk *clk;
 
 	clk_mux = kzalloc(sizeof(*clk_mux), GFP_KERNEL);

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