Re: [PATCH 1/2] clk: Fix error handling in fixed clock hardware type register fn

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On 03/20/2012 05:13 PM, Turquette, Mike wrote:
On Tue, Mar 20, 2012 at 12:46 AM, Saravana Kannan
<skannan@xxxxxxxxxxxxxx>  wrote:
On Tue, March 20, 2012 12:19 am, Sascha Hauer wrote:
On Mon, Mar 19, 2012 at 08:38:25PM -0700, Saravana Kannan wrote:
If memory allocation for the parents array or the parent string fails,
fail the registration immediately instead of calling clk_register and
hoping it fails there.

Return -ENOMEM on failure.

Signed-off-by: Saravana Kannan<skannan@xxxxxxxxxxxxxx>
Cc: Mike Turquette<mturquette@xxxxxxxxxx>
Cc: Andrew Lunn<andrew@xxxxxxx>
Cc: Rob Herring<rob.herring@xxxxxxxxxxx>
Cc: Russell King<linux@xxxxxxxxxxxxxxxx>
Cc: Jeremy Kerr<jeremy.kerr@xxxxxxxxxxxxx>
Cc: Thomas Gleixner<tglx@xxxxxxxxxxxxx>
Cc: Arnd Bergman<arnd.bergmann@xxxxxxxxxx>
Cc: Paul Walmsley<paul@xxxxxxxxx>
Cc: Shawn Guo<shawn.guo@xxxxxxxxxxxxx>
Cc: Sascha Hauer<s.hauer@xxxxxxxxxxxxxx>
Cc: Jamie Iles<jamie@xxxxxxxxxxxxx>
Cc: Richard Zhao<richard.zhao@xxxxxxxxxx>
Cc: Saravana Kannan<skannan@xxxxxxxxxxxxxx>
Cc: Magnus Damm<magnus.damm@xxxxxxxxx>
Cc: Mark Brown<broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: Linus Walleij<linus.walleij@xxxxxxxxxxxxxx>
Cc: Stephen Boyd<sboyd@xxxxxxxxxxxxxx>
Cc: Amit Kucheria<amit.kucheria@xxxxxxxxxx>
Cc: Deepak Saxena<dsaxena@xxxxxxxxxx>
Cc: Grant Likely<grant.likely@xxxxxxxxxxxx>
There are still some memory free issues when clk_register() fails, but I
fix it when I fixed the other register() fns to return ENOMEM of alloc
failure instead of a NULL.

  drivers/clk/clk-fixed-rate.c |   10 +++++++---
  1 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/clk-fixed-rate.c b/drivers/clk/clk-fixed-rate.c
index 90c79fb..6423ae9 100644
--- a/drivers/clk/clk-fixed-rate.c
+++ b/drivers/clk/clk-fixed-rate.c
@@ -61,22 +61,26 @@ struct clk *clk_register_fixed_rate(struct device
*dev, const char *name,
              parent_names = kmalloc(sizeof(char *), GFP_KERNEL);

              if (! parent_names)
-                    goto out;
+                    goto fail_ptr;

              len = sizeof(char) * strlen(parent_name);

              parent_names[0] = kmalloc(len, GFP_KERNEL);

              if (!parent_names[0])
-                    goto out;
+                    goto fail_str;

              strncpy(parent_names[0], parent_name, len);

It's easier to add a char *parent to struct clk_fixed and pass it to
clk_register with&fixed->parent. This saves you a kmalloc call and
makes the error path simpler. It's the same way already done in the

I thought I had done this for v7... hmm looks like one got left out.
I'll line up a patch to get it in sync with the others as part of my

I thought about that since I saw the same was done for gated and divider
(I think). Here is my guess at Mike's reasoning for this:

Gated and divider clocks have to have a parent. There's nothing to gate
otherwise. But fixed rate clocks might not have a parent. It could be XO's
or PLLs running off of always on XOs not controlled by the SoC. So, it's
arguable to not have a parent. I don't have a strong opinion on this --
since Mike took the time to write it, it left it to his subjective

I appreciate the thoughtfulness.  Re-using the same type of mechanism
as the divider and gate clocks will still allow the fixed-rate clock
to be parentless, and it makes for cleaner code, one less allocation
and lines up with how the other single-parent basic clocks are done,
so I'll take that method in instead of your patch.

No problem, go for it.

I sent this patch first since it was around the place I was cleaning up. I
didn't want to actually just shuffle around a bug. As I mentioned, this
patch still leaves a bug open -- what if clk_register() fails. I plan to
fix that once my two patches are picked up (hopefully).

Do you still find it useful to return -ENOMEM from the registration
function instead of a NULL clock?  I'm always worried that people
don't check for error codes on pointers in their platform code and
only check for NULL...

The last discussion I remember, NULL was considered a valid clock. So, I think on error, we shouldn't ever return NULL when the return type is struct clk *.


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