Hi Geert,

On Mon, May 8, 2017 at 11:08 PM, Geert Uytterhoeven
[off-list ref] wrote:

Hi Dong,

On Mon, May 8, 2017 at 4:03 PM, Dong Aisheng [off-list ref] wrote:

quoted

--- /dev/null
+++ b/drivers/clk/clk-bulk.c

@@ -0,0 +1,165 @@

quoted

+int __must_check clk_bulk_get(struct device *dev, int num_clks,
+                             struct clk_bulk_data *clks)
+{
+       int ret;
+       int i;
+
+       for (i = 0; i < num_clks; i++)
+               clks[i].clk = NULL;
+
+       for (i = 0; i < num_clks; i++) {
+               clks[i].clk = clk_get(dev, clks[i].id);
+               if (IS_ERR(clks[i].clk)) {
+                       ret = PTR_ERR(clks[i].clk);
+                       dev_err(dev, "Failed to get clk '%s': %d\n",
+                               clks[i].id, ret);
+                       clks[i].clk = NULL;
+                       goto err;
+               }
+       }
+
+       return 0;
+
+err:
+       while (--i >= 0)
+               clk_put(clks[i].clk);

These are released in inverse order, which is good.

quoted

+
+       return ret;
+}
+EXPORT_SYMBOL(clk_bulk_get);
+
+void clk_bulk_put(int num_clks, struct clk_bulk_data *clks)
+{
+       int i;
+
+       for (i = 0; i < num_clks; i++) {
+               clk_put(clks[i].clk);
+               clks[i].clk = NULL;

These aren't.

Typically resources are released in the inverse order. Not doing so may
cause subtle issues.

I can't come up with an example. but I'm quite sure the real world will find
one soon ;-)

The same is true for enable vs. disable, and prepare vs. unprepare.

I thought of it before and was wondering whether it's necessary to do it
as i believe it may be wrong for drivers to reply on the clk_bulk API to
do some some magic ordering to make things run because the API does not
guarantee it.

But i do agree with you that it might be a common sense to release resource
in inverse order, just harmless to do it!
So i will make it in V3 if no objection from Maintainer later.

Thanks for your suggestion!

Regards
Dong Aisheng

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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