On 07/19/2012 04:41 PM, Laurent Pinchart wrote:
> On Thursday 19 July 2012 16:02:41 Laurent Pinchart wrote:
>> On Thursday 19 July 2012 15:55:56 Lars-Peter Clausen wrote:
>>> On 07/19/2012 03:33 PM, Laurent Pinchart wrote:
>>>> On Thursday 19 July 2012 15:34:26 Lars-Peter Clausen wrote:
>>>>> On 07/19/2012 02:46 PM, Laurent Pinchart wrote:
>>>>>> On Monday 02 July 2012 16:37:47 Lars-Peter Clausen wrote:
>>>>>>> This patchset introduces a set of helper function for implementing
>>>>>>> the KMS framebuffer layer for drivers which use the drm gem CMA
>>>>>>> helper function.
>>>>>>>
>>>>>>> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
>>>>>>>
>>>>>>> ---
>>>>>>> Note: This patch depends on Sascha's "DRM: add drm gem CMA helper"
>>>>>>> patch
>>>>>>>
>>>>>>> Changes since v2:
>>>>>>> * Adapt to changes in the GEM CMA helper
>>>>>>> * Add basic buffer size checking in drm_fb_cma_create
>>>>>>>
>>>>>>> Changes since v1:
>>>>>>> * Some spelling fixes
>>>>>>> * Add missing kfree in drm_fb_cma_alloc error path
>>>>>>> * Add multi-plane support
>>>>>>>
>>>>>>> ---
>>>>>>>
>>>>>>> drivers/gpu/drm/Kconfig | 10 +
>>>>>>> drivers/gpu/drm/Makefile | 1 +
>>>>>>> drivers/gpu/drm/drm_fb_cma_helper.c | 393
>>>>>>> +++++++++++++++++++++++++++
>>>>>>> include/drm/drm_fb_cma_helper.h | 27 +++
>>>>>>> 4 files changed, 431 insertions(+)
>>>>>>> create mode 100644 drivers/gpu/drm/drm_fb_cma_helper.c
>>>>>>> create mode 100644 include/drm/drm_fb_cma_helper.h
>>>>>>
>>>>>> [snip]
>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c
>>>>>>> b/drivers/gpu/drm/drm_fb_cma_helper.c new file mode 100644
>>>>>>> index 0000000..9042233
>>>>>>> --- /dev/null
>>>>>>> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
>>>>>>
>>>>>> [snip]
>>>>>>
>>>>>>> +/**
>>>>>>> + * drm_fb_cma_create() - (struct drm_mode_config_funcs *)->fb_create
>>>>>>> callback function
>>>>>>> + *
>>>>>>> + * If your hardware has special alignment or pitch requirements
>>>>>>> these
>>>>>>> should be
>>>>>>> + * checked before calling this function.
>>>>>>> + */
>>>>>>> +struct drm_framebuffer *drm_fb_cma_create(struct drm_device *dev,
>>>>>>> + struct drm_file *file_priv, struct drm_mode_fb_cmd2 *mode_cmd)
>>>>>>> +{
>>>>>>> + struct drm_fb_cma *fb_cma;
>>>>>>> + struct drm_gem_cma_object *objs[4];
>>>>>>> + struct drm_gem_object *obj;
>>>>>>> + int ret;
>>>>>>> + int i;
>>>>>>> +
>>>>>>> + for (i = 0; i < drm_format_num_planes(mode_cmd->pixel_format);
> i++)
>>>>>>> {
>>>>>>> + obj = drm_gem_object_lookup(dev, file_priv, mode_cmd-
>>>>>
>>>>> handles[i]);
>>>>>
>>>>>>> + if (!obj) {
>>>>>>> + dev_err(dev->dev, "Failed to lookup GEM object\n");
>>>>>>> + ret = -ENXIO;
>>>>>>> + goto err_gem_object_unreference;
>>>>>>> + }
>>>>>>> +
>>>>>>> + if (obj->size < mode_cmd->height * mode_cmd->pitches[i]) {
>>>>>>
>>>>>> Shouldn't this be
>>>>>>
>>>>>> if (obj->size < mode_cmd->height * mode_cmd->pitches[i]
>>>>>>
>>>>>> + mode_cmd->offsets[i])
>>>>>>
>>>>>> ?
>>>>>
>>>>> That's actually a good question. I'd expect the offset to be included
>>>>> in the pitch.
>>>>>
>>>>> If you access pixels like mem[offset + x * bpp + y * pitch] then pitch
>>>>> has to be greater equal to offset + max_x * bpp, otherwise you'd have
>>>>> overlapping lines.
>>>>
>>>> My understanding is that the offset is a linear offset from the start of
>>>> the buffer to allow X/Y panning. In that case the pitch is a frame
>>>> buffer property that is not be influenced by the offset at all.
>>>
>>> Hi,
>>>
>>> I think panning is normally done by setting the x and y offset for the
>>> crtc.
>>>
>>> But yes, you are right the offset might just be a linear offset to the
>>> start of the actual data. I was just thinking about the case where the
>>> different planes are interleaved. But for panning or non-interleaved
>>> planes it obviously is different.
>>>
>>> Though this leaves us with a problem. If the planes are interleaved and
>>> the offset is included in the pitch your check may fail, even though the
>>> buffer is large enough.
>>>
>>> Maybe we need to handle both cases differently. If offset < pitch check
>>> for
>>> obj->size < mode_cmd->height * mode_cmd->pitches[i] otherwise check for
>>> obj->size < mode_cmd->height * mode_cmd->pitches[i] + mode_cmd->offsets[i]
>>>
>>> But that doesn't quite work either if you have both interleaved planes and
>>> a linear offset...
>>
>> What about first finding out what those offsets are supposed to be used for
>> ?
>>
>> Ville, git blame points to you as the author of the offsets field :-) Could
>> you please comment on this ?
>
> My bad, I was looking at drm_framebuffer and not drm_mode_fb_cmd2.
>
> Offset really looks like it is a linear offset from the beginning of the
> buffer. This allows placing several planes at different locations in a single
> buffer. I think we need to add mode_cmd->offsets[i] unconditionally when
> checking the size.
>
There are two cases to consider interleaved and non-interleaved planes in a
single buffer.
a) Separate planes
[Y Y Y Y ....]
[Y Y Y Y ....]
[ .......... ]
[Y Y Y Y ....]
[CBCR CBCR CBCR CBCR .... ]
[CBCR CBCR CBCR CBCR .... ]
[ ....................... ]
[CBCR CBCR CBCR CBCR .... ]
Plane 0:
bpp = 1
offset = 0
Plane 1:
bpp = 1
offset = plane0_size
b) Interleaved planes
[Y CBCR Y CBCR Y CBCR ....]
[Y CBCR Y CBCR Y CBCR ....]
[ ....................... ]
[Y CBCR Y CBCR Y CBCR ....]
Plane 0:
bbp = 2
offset = 0
Plane 1:
bbp = 2
offset = 1
For case b) pitch * height + offset will point after the end of the buffer
by one pixel, which is the size of the Y component.
I think we need something like:
min_size = height * pitch;
min_size += offset - (bpp - drm_format_plane_cpp())
(bpp - drm_format_plane_cpp() is, so it will be zero for the separate planes
case,
And well something similar for horizontal subsampling.
- Lars
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