On Sat, 23 Apr 2022 12:12:51 -0300
Igor Torrente <igormtorrente@xxxxxxxxx> wrote:
> Hi Pekka,
>
> On 4/20/22 08:23, Pekka Paalanen wrote:
> > On Mon, 4 Apr 2022 17:45:11 -0300
> > Igor Torrente <igormtorrente@xxxxxxxxx> wrote:
> >
> >> This commit is the groundwork to introduce new formats to the planes and
> >> writeback buffer. As part of it, a new buffer metadata field is added to
> >> `vkms_writeback_job`, this metadata is represented by the `vkms_composer`
> >> struct.
> >
> > Hi,
> >
> > should this be talking about vkms_frame_info struct instead?
>
> Yes it should. I will fix this. Thanks.
>
> >
> >>
> >> Also adds two new function pointers (`{wb,plane}_format_transform_func`)
> >> are defined to handle format conversion to/from internal format.
> >>
> >> These things will allow us, in the future, to have different compositing
> >> and wb format types.
> >>
> >> V2: Change the code to get the drm_framebuffer reference and not copy its
> >> contents(Thomas Zimmermann).
> >> V3: Drop the refcount in the wb code(Thomas Zimmermann).
> >> V5: Add {wb,plane}_format_transform_func to vkms_writeback_job
> >> and vkms_plane_state (Pekka Paalanen)
> >>
> >> Signed-off-by: Igor Torrente <igormtorrente@xxxxxxxxx>
> >> ---
> >> drivers/gpu/drm/vkms/vkms_composer.c | 4 ++--
> >> drivers/gpu/drm/vkms/vkms_drv.h | 31 +++++++++++++++++++++------
> >> drivers/gpu/drm/vkms/vkms_plane.c | 10 ++++-----
> >> drivers/gpu/drm/vkms/vkms_writeback.c | 20 ++++++++++++++---
> >> 4 files changed, 49 insertions(+), 16 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> >> index 2d946368a561..95029d2ebcac 100644
> >> --- a/drivers/gpu/drm/vkms/vkms_composer.c
> >> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> >> @@ -153,7 +153,7 @@ static void compose_plane(struct vkms_frame_info *primary_plane_info,
> >> struct vkms_frame_info *plane_frame_info,
> >> void *vaddr_out)
> >> {
> >> - struct drm_framebuffer *fb = &plane_frame_info->fb;
> >> + struct drm_framebuffer *fb = plane_frame_info->fb;
> >> void *vaddr;
> >> void (*pixel_blend)(const u8 *p_src, u8 *p_dst);
> >>
> >> @@ -175,7 +175,7 @@ static int compose_active_planes(void **vaddr_out,
> >> struct vkms_frame_info *primary_plane_info,
> >> struct vkms_crtc_state *crtc_state)
> >> {
> >> - struct drm_framebuffer *fb = &primary_plane_info->fb;
> >> + struct drm_framebuffer *fb = primary_plane_info->fb;
> >> struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
> >> const void *vaddr;
> >> int i;
> >> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> >> index 2e6342164bef..2704cfb6904b 100644
> >> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> >> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> >> @@ -22,13 +22,8 @@
> >>
> >> #define NUM_OVERLAY_PLANES 8
> >>
> >> -struct vkms_writeback_job {
> >> - struct dma_buf_map map[DRM_FORMAT_MAX_PLANES];
> >> - struct dma_buf_map data[DRM_FORMAT_MAX_PLANES];
> >> -};
> >> -
> >> struct vkms_frame_info {
> >> - struct drm_framebuffer fb;
> >> + struct drm_framebuffer *fb;
> >> struct drm_rect src, dst;
> >> struct dma_buf_map map[DRM_FORMAT_MAX_PLANES];
> >> unsigned int offset;
> >> @@ -36,6 +31,29 @@ struct vkms_frame_info {
> >> unsigned int cpp;
> >> };
> >>
> >> +struct pixel_argb_u16 {
> >> + u16 a, r, g, b;
> >> +};
> >> +
> >> +struct line_buffer {
> >> + size_t n_pixels;
> >> + struct pixel_argb_u16 *pixels;
> >> +};
> >> +
> >> +typedef void
> >> +(*wb_format_transform_func)(struct vkms_frame_info *frame_info,
> >> + const struct line_buffer *buffer, int y);
> >> +
> >> +typedef void
> >> +(*plane_format_transform_func)(struct line_buffer *buffer,
> >> + const struct vkms_frame_info *frame_info, int y);
> >
> > It wasn't immediately obvious to me in which direction these function
> > types work from their names. The arguments are not wb and plane but
> > vkms_frame_info and line_buffer in both. The implementations of these
> > functions would have nothing specific to a wb or a plane either, would
> > they?
>
> No, there's nothing specific.
>
> Do you think adding {dst_,src_} would be enough?
>
> (*wb_format_transform_func)(struct vkms_frame_info *dst_frame_info,
> const struct line_buffer *src_buffer
>
> (*plane_format_transform_func)(struct line_buffer *dst_buffer,
> const struct vkms_frame_info *src_frame_info,
No, because I was looking at the function pointer type names, and not
the function arguments.
> >
> > What about naming them frame_to_line_func and line_to_frame_func?
>
> Sounds good. I will rename it.
Thanks!
> >> +
> >> +struct vkms_writeback_job {
> >> + struct dma_buf_map data[DRM_FORMAT_MAX_PLANES];
> >> + struct vkms_frame_info frame_info;
> >
> > Which frame_info is this? Should the field be called wb_frame_info?
>
> Considering it's already in the writeback_job struct do you think this
> necessary?
This struct has 'data' too, and that is not the wb buffer, right?
Hmm, if it's not the wb buffer, then using DRM_FORMAT_MAX_PLANES is
odd...
> In other words, what kind of misudertanding do you think can happen if
> this variable stay without the `wb_` prefix?
>
> I spent a few minutes trying to find a case, but nothing came to my
> mind.
My question above is the confusion.
If all these members are about the wb destination buffer only, then
where do the inputs come from and how are they reference-counted to
make sure they are available when needed?
> >> + wb_format_transform_func format_func;
> >
> > line_to_frame_func wb_write;
> >
> > perhaps? The type explains the general type of the function, and the
> > field name refers to what it is used for.
> >
> >> +};
> >> +
> >> /**
> >> * vkms_plane_state - Driver specific plane state
> >> * @base: base plane state
> >> @@ -44,6 +62,7 @@ struct vkms_frame_info {
> >> struct vkms_plane_state {
> >> struct drm_shadow_plane_state base;
> >> struct vkms_frame_info *frame_info;
> >> + plane_format_transform_func format_func;
> >
> > Similarly here, maybe
> >
> > frame_to_line_func plane_read;
> >
> > perhaps?
>
> Yeah, sure.
>
> >
> >> };
> >>
> >> struct vkms_plane {
> >> diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> >> index a56b0f76eddd..28752af0118c 100644
> >> --- a/drivers/gpu/drm/vkms/vkms_plane.c
> >> +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> >> @@ -50,12 +50,12 @@ static void vkms_plane_destroy_state(struct drm_plane *plane,
> >> struct vkms_plane_state *vkms_state = to_vkms_plane_state(old_state);
> >> struct drm_crtc *crtc = vkms_state->base.base.crtc;
> >>
> >> - if (crtc) {
> >> + if (crtc && vkms_state->frame_info->fb) {
> >> /* dropping the reference we acquired in
> >> * vkms_primary_plane_update()
> >> */
> >> - if (drm_framebuffer_read_refcount(&vkms_state->frame_info->fb))
> >> - drm_framebuffer_put(&vkms_state->frame_info->fb);
> >> + if (drm_framebuffer_read_refcount(vkms_state->frame_info->fb))
> >> + drm_framebuffer_put(vkms_state->frame_info->fb);
> >> }
> >>
> >> kfree(vkms_state->frame_info);
> >> @@ -110,9 +110,9 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
> >> frame_info = vkms_plane_state->frame_info;
> >> memcpy(&frame_info->src, &new_state->src, sizeof(struct drm_rect));
> >> memcpy(&frame_info->dst, &new_state->dst, sizeof(struct drm_rect));
> >> - memcpy(&frame_info->fb, fb, sizeof(struct drm_framebuffer));
> >> + frame_info->fb = fb;
> >
> > This change, replacing the memcpy with storing a pointer, seems to be
> > another major point of this patch. Should it be a separate patch?
> > It doesn't seem to fit with the current commit message.
> >
> > I have no idea what kind of locking or referencing a drm_framebuffer
> > would need, and I suspect that would be easier to review if it was a
> > patch of its own.
>
> Makes sense. I will do that.
>
> >
> >> memcpy(&frame_info->map, &shadow_plane_state->data, sizeof(frame_info->map));
> >> - drm_framebuffer_get(&frame_info->fb);
> >> + drm_framebuffer_get(frame_info->fb);
> >
> > Does drm_framebuffer_get() not return anything?
>
> No, it doesn't actually. This function increments the ref count of this
> struct and doesn't return anything.
D'oh. Oh well.
Thanks,
pq
> >
> > To me it would be more idiomatic to write something like
> >
> > frame_info->fb = drm_framebuffer_get(fb);
> > I spend few minutes trying to find a case but nothing comes to my mind.
> > I don't know if that pattern is used in the kernel, but I use it in
> > userspace to emphasise that frame_info owns a new reference rather than
> > borrowing someone else's.
> >
> >
> > Thanks,
> > pq
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