Re: [PATCH v3] drm/i915: Implement dma-buf mmap() for userspace access

[Ander Conselvan de Oliveira <conselvan2@gmail.com>]

On 06/19/2014 03:37 PM, Daniel Vetter wrote:
> On Thu, Jun 19, 2014 at 03:34:34PM +0300, Ander Conselvan de Oliveira wrote:
>> From: Rob Bradford <rob@linux.intel.com>
>>
>> The aim is that this is functionally equivalent to using the
>> I915_GEM_MMAP ioctl.
>>
>> v2: Add aperture check limit, limit to SNB+ and improve error handling.
>>
>> v3 (anderco): Map without using the GTT.
>
> Why that? This means you'll have a non-coherent mapping and atm dma-buf
> doesn't expose and invalidate/flushing ioctls. Which really you want for
> this.

Hmm. I completely overlooked that important detail. In a discussion with 
Rob, we came to the conclusion we didn't want to use the GTT because of 
the performance penalty. Now I see that just modifying the mmap() 
support is not enough.

Thanks,
Ander

> -Daniel
>
>>
>> Signed-off-by: Rob Bradford <rob@linux.intel.com>
>> Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
>> ---
>>   drivers/gpu/drm/i915/i915_gem_dmabuf.c | 19 ++++++++++++++++++-
>>   1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
>> index 580aa42..2d31fca 100644
>> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
>> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
>> @@ -193,7 +193,24 @@ static void i915_gem_dmabuf_kunmap(struct dma_buf *dma_buf, unsigned long page_n
>>
>>   static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma)
>>   {
>> -	return -EINVAL;
>> +	struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
>> +	struct drm_device *dev = obj->base.dev;
>> +	struct drm_i915_private *dev_priv = dev->dev_private;
>> +	int ret;
>> +
>> +	if (INTEL_INFO(dev)->gen < 6)
>> +		return -EINVAL;
>> +
>> +	ret = i915_mutex_lock_interruptible(dev);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = obj->base.filp->f_op->mmap(obj->base.filp, vma);
>> +	fput(vma->vm_file);
>> +	vma->vm_file = get_file(obj->base.filp);
>> +
>> +	mutex_unlock(&dev->struct_mutex);
>> +	return ret;
>>   }
>>
>>   static int i915_gem_begin_cpu_access(struct dma_buf *dma_buf, size_t start, size_t length, enum dma_data_direction direction)
>> --
>> 1.8.3.2
>>
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>