On Tue, 29 Nov 2022 18:10:30 +0800
Hsia-Jun Li <randy.li@xxxxxxxxxxxxx> wrote:
> From: "Hsia-Jun(Randy) Li" <randy.li@xxxxxxxxxxxxx>
>
> Hello All
>
> Currently, we assume all the pixel formats are multiple planes,
Hi,
that's not true for any definition of "multiple planes" that I know of.
For example, DRM_FORMAT_XRGB8888 is a single-plane format by definition.
From below it sounds like you mean "physically non-contiguous". But no,
pixel formats make no such assumption at all. Contiguous or not is
independent of pixel formats.
> devices
> could support each component has its own memory plane.
> But that may not apply for any device in the world. We could have a
> device without IOMMU then this is not impossible.
>
> Besides, when we export an handle through the PRIME, the upstream
> device(likes a capture card or camera) may not support non-contiguous
> memory. It would be better to allocate the handle in contiguous memory
> at the first time.
>
> We may think the memory allocation is done in user space, we could do
> the trick there. But the dumb_create() sometimes is not the right API
> for that.
>
> "Note that userspace is not allowed to use such objects for render
> acceleration - drivers must create their own private ioctls for such a
> use case."
> "Note that dumb objects may not be used for gpu acceleration, as has
> been attempted on some ARM embedded platforms. Such drivers really must
> have a hardware-specific ioctl to allocate suitable buffer objects."
>
> We need to relay on those device custom APIs then. It would be helpful
> for their library to calculate the right size for contiguous memory. It
> would be useful for the driver supports rendering dumb buffer as well.
>
> Signed-off-by: Hsia-Jun(Randy) Li <randy.li@xxxxxxxxxxxxx>
> ---
> include/uapi/drm/drm_fourcc.h | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index bc056f2d537d..ec039ced8257 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -473,6 +473,11 @@ extern "C" {
> */
> #define DRM_FORMAT_MOD_LINEAR fourcc_mod_code(NONE, 0)
>
> +/*
> + * Contiguous memory
> + */
> +#define DRM_FORMAT_MOD_CONTIG_MEM fourcc_mod_code(NONE, 1)
NAK. This is not what modifiers are for.
This also would not work in practise, because if this was a modifier,
you would not be able to use the actual modifiers.
Thanks,
pq
> +
> /*
> * Deprecated: use DRM_FORMAT_MOD_LINEAR instead
> *
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