[Mesa-dev] Nouveau driver problem when using EGL_LINUX_DMA_BUF_EXT

[Volker Vogelhuber]

Not sure if this is the right mailing list, or if the problem may belong 
to the libdrm part.
I'm currently trying to import a DMABUF from V4L2 UVC source (using 
VIDIOC_EXPBUF) into OpenGL using EGL_LINUX_DMA_BUF_EXT. While this is 
working fine with the i915 driver it fails with the Nouveau driver.
As a test case I have a UVC camera with a resolution of 400x400 and an 
8bit raw bayer format. So the following attributes are set during the 
EGL image creation:

// Texture width
attrs.push_back(EGL_WIDTH);
attrs.push_back(400);
// Texture height
attrs.push_back(EGL_HEIGHT);
attrs.push_back(400);
// Color
attrs.push_back(EGL_LINUX_DRM_FOURCC_EXT);
attrs.push_back(DRM_FORMAT_R8);
// FD
attrs.push_back(EGL_DMA_BUF_PLANE0_FD_EXT);
attrs.push_back(fd);
// Offset
attrs.push_back(EGL_DMA_BUF_PLANE0_OFFSET_EXT);
attrs.push_back(0);
// Pitch
attrs.push_back(EGL_DMA_BUF_PLANE0_PITCH_EXT);
attrs.push_back(400);

eglCreateImage( eglGetCurrentDisplay(), EGL_NO_CONTEXT, 
EGL_LINUX_DMA_BUF_EXT, NULL, &attrs[0] );

So far no error or any other problem. But when I want to render the 
image it is distorted, like if the stride is not correct. I debugged 
into the system libraries but couldn't find any code that may give a 
hint if there are some constraints to be met regarding the stride when 
importing a DMABUF into the nouveau driver. The only thing I found was 
while the size of the V4L2 buffer is 400x400x1 = 160000 the size 
returned by

drmCommandWriteRead(drm->fd, DRM_NOUVEAU_GEM_INFO, &req, sizeof(req));

in the libdrm nouveau part returned a page aligned size of 163840 bytes.

While the sample case with this camera only resulted in a wrongly 
displayed image, I also have another V4L2 source with RGBX format where 
using the texture with DMABUF even results in a total crash of my 
machine. I haven't debugged that case further as I wanted to resolve the 
issue with the 400x400 image first (debugging is easier if the machine 
does not freeze all the time).

I'm currently running Ubuntu 17.10 with libdrm 2.4.83 and mesa 17.2.8. 
So the libraries are not the most current one. Are there any known 
issues for my use case?