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

[Ben Skeggs]

On 3 September 2015 at 17:18, Alexandre Courbot <gnurou at gmail.com> wrote:
> On Thu, Sep 3, 2015 at 4:16 PM, Ben Skeggs <skeggsb at gmail.com> wrote:
>> 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.
>
> Ok then. I will wait for your feedback on patch 3/3 before resending.
3/3 looks fine to me from a quick glance, I'll take your word that it
works, and it doesn't effect dGPUs at all anyway :)