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

[Alexandre Courbot]

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.