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

[Turquette, Mike]

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,
>>> then
>>> 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
>>> will
>>> 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
>> divider.

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
fixes.

> 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
> preference.

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.

> 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...

Regards,
Mike

> Thanks,
> Saravana
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