Skip to content

drm: align plane destination size to even pixels #142

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
henkwiedig merged 1 commit into from
Aug 2, 2026
Merged

drm: align plane destination size to even pixels #142

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
80 changes: 52 additions & 28 deletions src/drm.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -672,6 +672,51 @@ struct modeset_output *modeset_prepare(int fd, uint16_t mode_width, uint16_t mod
return NULL;
}

/*
* Aspect-preserving, centred destination rectangle for a src_w x src_h source
* scaled by out->video_scale_factor.
*
* The width is rounded down to an even number of pixels when, and only when, it
* is a horizontal scale DOWN. RK3566/3568 VOP2 Esmart/Smart windows cannot
* scale down to an odd destination width; the driver trims the pixel itself and
* logs
*
* [drm] vp0 Esmart0-win0 dsp_w[1843] MODE 2 == 1 at scale down mode
*
* on every atomic commit, i.e. at frame rate. An odd width comes up easily:
* 1920 * 0.96 = 1843, and the aspect fit alone yields 1905 for a 1920x1088
* source even at scale factor 1.0. Aligning here keeps the log clean and makes
* the geometry we ask for the geometry we actually get.
*
* The restriction is horizontal-scale-down only: the driver gates the warning on
* actual_w > dsp_w, and has no equivalent constraint on the destination height.
* So do not touch the height, and do not shave a pixel off a width that is being
* upscaled or passed through 1:1 — that would shrink the picture for nothing.
*/
static void video_dst_rect(const struct modeset_output *out, uint32_t src_w, uint32_t src_h,
int *dst_x, int *dst_y, uint32_t *dst_w, uint32_t *dst_h)
{
uint32_t fit_w = out->video_crtc_width;
uint32_t fit_h = out->video_crtc_height;
float ratio = src_h ? (float)src_w / src_h : 1.0f;

if (fit_w / ratio > fit_h)
fit_w = (uint32_t)(fit_h * ratio);
else
fit_h = (uint32_t)(fit_w / ratio);

uint32_t w = (uint32_t)(fit_w * out->video_scale_factor);
uint32_t h = (uint32_t)(fit_h * out->video_scale_factor);

if (w < src_w)
w &= ~1u;

*dst_w = w;
*dst_h = h;
*dst_x = (out->video_crtc_width - (int)w) / 2;
*dst_y = (out->video_crtc_height - (int)h) / 2;
}

void modeset_apply_video_scale(int fd, struct modeset_output *out)
{
drmModePlane *plane = drmModeGetPlane(fd, out->video_plane.id);
Expand All @@ -685,17 +730,10 @@ void modeset_apply_video_scale(int fd, struct modeset_output *out)
if (!fb_id) return;

/* Recalculate geometry (same logic as modeset_atomic_prepare_commit) */
uint32_t orig_crtcw = out->video_crtc_width;
uint32_t orig_crtch = out->video_crtc_height;
float video_ratio = (float)out->video_frm_width / out->video_frm_height;
if (orig_crtcw / video_ratio > orig_crtch)
orig_crtcw = (uint32_t)(orig_crtch * video_ratio);
else
orig_crtch = (uint32_t)(orig_crtcw / video_ratio);
uint32_t crtcw = (uint32_t)(orig_crtcw * out->video_scale_factor);
uint32_t crtch = (uint32_t)(orig_crtch * out->video_scale_factor);
int crtcx = (out->video_crtc_width - crtcw) / 2;
int crtcy = (out->video_crtc_height - crtch) / 2;
uint32_t crtcw, crtch;
int crtcx, crtcy;
video_dst_rect(out, out->video_frm_width, out->video_frm_height,
&crtcx, &crtcy, &crtcw, &crtch);

/*
* Update only the video plane geometry — do NOT touch CRTC/connector
Expand Down Expand Up @@ -769,24 +807,10 @@ int modeset_atomic_prepare_commit(int fd, struct modeset_output *out, drmModeAto
if (set_drm_object_property(req, plane, "SRC_H", height << 16) < 0)
return -1;

uint32_t orig_crtcw = out->video_crtc_width;
uint32_t orig_crtch = out->video_crtc_height;
float video_ratio = (float)width / height;
if (orig_crtcw / video_ratio > orig_crtch) {
orig_crtcw = orig_crtch * video_ratio;
orig_crtch = orig_crtch;
} else {
orig_crtcw = orig_crtcw;
orig_crtch = orig_crtcw / video_ratio;
}


float scale_factor = out->video_scale_factor;
uint32_t crtcw = (uint32_t)(orig_crtcw * scale_factor);
uint32_t crtch = (uint32_t)(orig_crtch * scale_factor);
uint32_t crtcw, crtch;
int crtcx, crtcy;
video_dst_rect(out, width, height, &crtcx, &crtcy, &crtcw, &crtch);

int crtcx = (out->video_crtc_width - crtcw) / 2;
int crtcy = (out->video_crtc_height - crtch) / 2;
if (set_drm_object_property(req, plane, "CRTC_X", crtcx) < 0)
return -1;
if (set_drm_object_property(req, plane, "CRTC_Y", crtcy) < 0)
Expand Down