[bug report] perf: xgene: Add APM X-Gene SoC Performance Monitoring Unit driver

[mark.rutland@arm.com (Mark Rutland)]

Hi Dan,

Thanks for the report.

On Wed, Oct 12, 2016 at 02:32:29PM +0300, Dan Carpenter wrote:
> The patch 832c927d119b: "perf: xgene: Add APM X-Gene SoC Performance
> Monitoring Unit driver" from Jul 15, 2016, leads to the following
> static checker warning:
> 
> 	drivers/perf/xgene_pmu.c:1014 acpi_get_pmu_hw_inf()
> 	warn: '&res' isn't an ERR_PTR
> 
> drivers/perf/xgene_pmu.c
>    992  static struct
>    993  xgene_pmu_dev_ctx *acpi_get_pmu_hw_inf(struct xgene_pmu *xgene_pmu,
>    994                                         struct acpi_device *adev, u32 type)
>    995  {
>    996          struct device *dev = xgene_pmu->dev;
>    997          struct list_head resource_list;
>    998          struct xgene_pmu_dev_ctx *ctx;
>    999          const union acpi_object *obj;
>   1000          struct hw_pmu_info *inf;
>   1001          void __iomem *dev_csr;
>   1002          struct resource res;
>   1003          int enable_bit;
>   1004          int rc;
>   1005  
>   1006          ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
>   1007          if (!ctx)
>   1008                  return NULL;
>   1009  
>   1010          INIT_LIST_HEAD(&resource_list);
>   1011          rc = acpi_dev_get_resources(adev, &resource_list,
>   1012                                      acpi_pmu_dev_add_resource, &res);
>   1013          acpi_dev_free_resource_list(&resource_list);
>   1014          if (rc < 0 || IS_ERR(&res)) {
>                                      ^^^^
> Obviously this is a stack address and not an error pointer.  I'm not
> sure what was intended here.

Urrgh; I should have caught that in review. It's been this way since v1 [1], so
I can't reverse-engineer the intent. However, I don't believe that it's
necessary to check anything other than the rc value here.

This should always evaluate as false, and shouldn't result in a functional
problem, but it is completely bogus.

Tai, can you plase send a patch deleting The IS_ERR() check here?

Thanks,
Mark.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-March/419173.html