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example: improve CRTC search algorithm

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Add a fallback case for finding an eligible CRTC for the
selected connector. The encoder picked may not have been
wired up to that connector by the previous DRM master.
This commit is contained in:
Matt Hoosier 2019-11-07 16:03:41 -06:00 committed by Simon Ser
parent d51e2fb2fe
commit 78cc612f10
1 changed files with 35 additions and 4 deletions
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35
example/common.c
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@ -1,5 +1,6 @@
#include <assert.h>
#include <drm_fourcc.h>
#include <stdio.h>
#include <stddef.h>
#include <sys/mman.h>
#include <xf86drm.h>
@ -26,13 +27,43 @@ drmModeCrtc *pick_crtc(int drm_fd, drmModeRes *drm_res,
{
drmModeEncoder *enc;
uint32_t crtc_id;
int i;
int j;
bool found;
/* TODO: don't blindly use current CRTC */
enc = drmModeGetEncoder(drm_fd, connector->encoder_id);
if (enc) {
/* Current CRTC happens to be usable on the selected connector */
crtc_id = enc->crtc_id;
drmModeFreeEncoder(enc);
return drmModeGetCrtc(drm_fd, crtc_id);
} else {
/* Current CRTC used by this encoder can't drive the selected connector.
* Search all of them for a valid combination. */
for (i = 0, found = false; !found && i < connector->count_encoders; i++) {
enc = drmModeGetEncoder(drm_fd, connector->encoders[i]);
if (!enc) {
continue;
}
for (j = 0; !found && j < drm_res->count_crtcs; j++) {
/* Can the CRTC drive the connector? */
if (enc->possible_crtcs & (1 << j)) {
crtc_id = drm_res->crtcs[j];
found = true;
}
}
drmModeFreeEncoder(enc);
}
if (found) {
return drmModeGetCrtc(drm_fd, crtc_id);
} else {
return NULL;
}
}
}
void disable_all_crtcs_except(int drm_fd, drmModeRes *drm_res, uint32_t crtc_id)