Re: [PATCH 2/4] drm/i915: Support for creating Stolen memory backed objects

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 07/01/2015 05:19 PM, Chris Wilson wrote:
> On Wed, Jul 01, 2015 at 04:06:49PM +0100, Tvrtko Ursulin wrote:
>>> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
>>> index c5349fa..6045749 100644
>>> --- a/drivers/gpu/drm/i915/i915_dma.c
>>> +++ b/drivers/gpu/drm/i915/i915_dma.c
>>> @@ -167,6 +167,9 @@ static int i915_getparam(struct drm_device *dev, void *data,
>>>   		value = i915.enable_hangcheck &&
>>>   			intel_has_gpu_reset(dev);
>>>   		break;
>>> +	case I915_PARAM_CREATE_VERSION:
>>> +		value = 1;
>>
>> Shouldn't it be 2?
>
> But 1 is the 2nd number, discounting all those pesky negative versions :)

It would be more obvious I think, even though I915_PARAM_CREATE_VERSION 
which returns 1 would never exist.

>>> +		ret = i915_gem_exec_clear_object(obj, file->driver_priv);
>>
>> I would put a comment here saying why it is important to clear
>> stolen memory.
>
> Userspace ABI (and kernel ABI in general) is that we do not hand back
> uncleared buffers. Something to do with bank card details I guess.
> So just:

Yes thats obvious - but where it is done for normal objects? Can't find 
it... is it hidden in shmemfs somewhere? If so reinforces the need for a 
comment here.

Regards,

Tvrtko
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