[PATCH 2/6] rtc: rtc-m48t86: add hooks to support driver side memory mapping

[Ryan Mallon]

On 02/04/13 10:42, Alexander Clouter wrote:
> On Tue, Apr 02, 2013 at 10:36:43AM +1100, Ryan Mallon wrote:
>> On 02/04/13 10:22, Alexander Clouter wrote:
>>> If platform_data is not defined (as before), then named memory io
>>> ranges need to be defined ("rtc_index" and "rtc_data").  The driver
>>> then maps those regions and uses them as the RTC index and data
>>> addresses.
>>>
>>> Does compile with the following warnings, I cannot see the codepath
>>> affected myself:
>>> ----
>>> drivers/rtc/rtc-m48t86.c: In function ‘m48t86_rtc_probe’:
>>> drivers/rtc/rtc-m48t86.c:180: warning: ‘res_index’ may be used
>>> uninitialized in this function
>>> drivers/rtc/rtc-m48t86.c:180: warning: ‘res_data’ may be used
>>> uninitialized in this function
>>
>> It is caused by the exit paths. If pdev->dev.platform_data is set, the
>> res_index and res_data are never initialised, but in the error case you
>> still for rtc_device_register you jump to out_io_data, which will then
>> dereference res_index/res_data. You need to make the exit paths
>> conditional on pdev->dev.platform_data (or init res_index/data to NULL
>> and make the release_mem_regions conditional on that).
> 
> However, the 'goto out_io_data' in the 'IS_ERR(priv->rtc)' is wrapped in
> a 'if (!pdev->dev.platform_data)', else we jump to out_free.

Ah right, I missed that. In that case, I can't see the problem either :-/.

> 
> I suspect I am probably missing something *too* obvious here for it to
> click?

It could be gcc being dumb, though this does seem a straight-forward
enough case for gcc to get it correct. It would be nice to get rid of
the warning though. Doing:

  struct resource *res_index = NULL; /* Avoid GCC warning */

Isn't too costly.

~Ryan