[Nouveau] [PATCH 2/2] gr/gf100: do not assume a PMU is present

[Ben Skeggs]

On 3 September 2015 at 17:11, Alexandre Courbot <gnurou at gmail.com> wrote:
> On Thu, Sep 3, 2015 at 4:08 PM, Ben Skeggs <skeggsb at gmail.com> wrote:
>> On 3 September 2015 at 16:32, Alexandre Courbot <acourbot at nvidia.com> wrote:
>>> Some devices may not have a PMU. Avoid a NULL pointer dereference in
>>> such cases.
>>>
>>> Signed-off-by: Alexandre Courbot <acourbot at nvidia.com>
>>> ---
>>>  drm/nouveau/nvkm/engine/gr/gf100.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drm/nouveau/nvkm/engine/gr/gf100.c b/drm/nouveau/nvkm/engine/gr/gf100.c
>>> index f1358a564e3e..f252fa2d7cf9 100644
>>> --- a/drm/nouveau/nvkm/engine/gr/gf100.c
>>> +++ b/drm/nouveau/nvkm/engine/gr/gf100.c
>>> @@ -1499,7 +1499,8 @@ gf100_gr_oneinit(struct nvkm_gr *base)
>>>         struct nvkm_device *device = gr->base.engine.subdev.device;
>>>         int ret, i, j;
>>>
>>> -       nvkm_pmu_pgob(device->pmu, false);
>>> +       if (device->pmu)
>>> +               nvkm_pmu_pgob(device->pmu, false);
>> I'd probably just change the condition in nvkm_pmu_pgob() to (pmu &&
>> pmu->func->pgob) ?
>
> It seems logical to me that the caller should check that the object it
> tries to call a method on is valid (just like in C++ you don't expect
> methods to check whether this == NULL), but your call.
Yeah, I had similar thoughts when writing some of these accessor
functions, and decided on treating them as "helper" functions that act
as a stub when the object doesn't exist or doesn't support a
particular function.  Mainly to avoid having duplicated checks in
multiple places that can get out of sync.