Bug 1156: DRM/GBM NEWT: Clarify drmModeSetCrtc(..)'s x/y parameter and earmark spanning across monitors

drmModeSetCrtc(..)'s x/y parameter are the surface's offset to be scanned out from one CRT!

1 files changed, 31 insertions, 50 deletions

diff --git a/src/newt/native/drm_gbm_legacy.c b/src/newt/native/drm_gbm_legacy.c
index cec3297a8..9c4e19dc3 100644
--- a/src/newt/native/drm_gbm_legacy.c
+++ b/src/newt/native/drm_gbm_legacy.c
@@ -43,7 +43,6 @@ gbm_bo_get_offset(struct gbm_bo *bo, int plane);
 typedef struct {
     struct gbm_bo *bo;
     uint32_t fb_id;
-    uint32_t x, y;
 } DRM_FB;
 
 static void page_flip_handler(int fd, unsigned int frame,
@@ -180,11 +179,12 @@ static DRM_FB * drm_fb_get_from_bo(int drmFd, struct gbm_bo *bo)
 }
 
 JNIEXPORT jlong JNICALL Java_jogamp_newt_driver_egl_gbm_WindowDriver_FirstSwapSurface0
-  (JNIEnv *env, jobject obj, jint drmFd, jint jcrtc_id, jint jx, jint jy, 
-   jint jconnector_id, jobject jmode, jint jmode_byte_offset, 
-   jlong jgbmSurface, jint swapInterval)
+  (JNIEnv *env, jobject obj, jint drmFd, jint jcrtc_id, jint jsurfaceOffsetX, jint jsurfaceOffsetY, 
+   jint jconnector_id, jobject jmode, jint jmode_byte_offset, jlong jgbmSurface)
 {
-    uint32_t crtc_id = (uint32_t)jcrtc_id;
+    const uint32_t crtc_id = (uint32_t)jcrtc_id;
+    const uint32_t surfaceOffsetX = (uint32_t)jsurfaceOffsetX;
+    const uint32_t surfaceOffsetY = (uint32_t)jsurfaceOffsetY;
     uint32_t connector_id = (uint32_t)jconnector_id;
     drmModeModeInfo *drmMode = NULL;
     struct gbm_surface *gbmSurface = (struct gbm_surface *) (intptr_t) jgbmSurface;
@@ -202,23 +202,34 @@ JNIEXPORT jlong JNICALL Java_jogamp_newt_driver_egl_gbm_WindowDriver_FirstSwapSu
         ERR_PRINT("Failed to get a new framebuffer BO (0)\n");
         return 0;
     }
-    fb->x = (uint32_t)jx;
-    fb->y = (uint32_t)jy;
     /**
      * Set Mode 
      *
      * Fails with x/y != 0: -28 No space left on device
      *   drmModeSetCrtc.0 failed to set mode: fd 26, crtc_id 0x27, fb_id 0x54, pos 10/10, conn_id 0x4d, curMode 1920x1080: -28 No space left on device
+     *
+     * See https://lists.freedesktop.org/archives/dri-devel/2014-February/053826.html:
+     *
+     * - The X,Y in drmModeSetCrtc does in fact specify the "source" offset into
+     *   your framebuffer (not the destination on the CRTC) which is what I was looking for.
+     *
+     * - We were able to allocate both a Dumb buffer, and a GBM buffer the size of
+     *   6 1920x1200 monitors in a 1x6 configuration, so basically we didn't have
+     *   any memory issues with a single buffer that big.
+     *
+     * - drmModeSetCrtc worked with both Dumb and GBM buffers, and we didn't have
+     *   to do anything special on our end, so it clearly is handling the tiling
+     *   issues behind the scenes (woot).
      */
-    ret = drmModeSetCrtc(drmFd, crtc_id, fb->fb_id, fb->x, fb->y,
+    ret = drmModeSetCrtc(drmFd, crtc_id, fb->fb_id, surfaceOffsetX, surfaceOffsetY,
                          &connector_id, 1, drmMode);
     if (ret) {
-        ERR_PRINT("drmModeSetCrtc.0 failed to set mode: fd %d, crtc_id 0x%x, fb_id 0x%x, pos %d/%d, conn_id 0x%x, curMode %s: %d %s\n", 
-            drmFd, crtc_id, fb->fb_id, jx, jy, connector_id, drmMode->name, ret, strerror(errno));
+        ERR_PRINT("drmModeSetCrtc.0 failed to set mode: fd %d, crtc_id 0x%x, fb_id 0x%x (offset %d/%d), conn_id 0x%x, curMode %s: %d %s\n", 
+            drmFd, crtc_id, fb->fb_id, surfaceOffsetX, surfaceOffsetY, connector_id, drmMode->name, ret, strerror(errno));
         return 0;
     }
-    DBG_PRINT( "EGL_GBM.Window FirstSwapSurface0 swapInterval %d, nextBO %p, fd %d, crtc_id 0x%x, fb_id 0x%x, pos %d/%d, conn_id 0x%x, curMode %s\n", 
-        swapInterval, nextBO, drmFd, crtc_id, fb->fb_id, jx, jy, connector_id, drmMode->name);
+    DBG_PRINT( "EGL_GBM.Window FirstSwapSurface0 nextBO %p, fd %d, crtc_id 0x%x, fb_id 0x%x (offset %d/%d), conn_id 0x%x, curMode %s\n", 
+        nextBO, drmFd, crtc_id, fb->fb_id, surfaceOffsetX, surfaceOffsetY, connector_id, drmMode->name);
     return (jlong) (intptr_t) nextBO;
 }
 
@@ -227,17 +238,16 @@ static int nextSwapVerboseOnce = 1;
 #endif
 
 JNIEXPORT jlong JNICALL Java_jogamp_newt_driver_egl_gbm_WindowDriver_NextSwapSurface0
-  (JNIEnv *env, jobject obj, jint drmFd, jint jcrtc_id, jint jx, jint jy, 
+  (JNIEnv *env, jobject obj, jint drmFd, jint jcrtc_id, 
    jint jconnector_id, jobject jmode, jint jmode_byte_offset, 
    jlong jgbmSurface, jlong jlastBO, jint swapInterval)
 {
-    uint32_t crtc_id = (uint32_t)jcrtc_id;
-    uint32_t x = (uint32_t)jx;
-    uint32_t y = (uint32_t)jy;
-    uint32_t connector_id = (uint32_t)jconnector_id;
+    const uint32_t crtc_id = (uint32_t)jcrtc_id;
+    const uint32_t connector_id = (uint32_t)jconnector_id;
     drmModeModeInfo *drmMode = NULL;
     struct gbm_surface *gbmSurface = (struct gbm_surface *) (intptr_t) jgbmSurface;
-    struct gbm_bo *lastBO = (struct gbm_bo*) (intptr_t) jlastBO, *nextBO = NULL;
+    struct gbm_bo *lastBO = (struct gbm_bo*) (intptr_t) jlastBO;
+    struct gbm_bo *nextBO = NULL;
     DRM_FB *fbNext = NULL;
     int ret, waiting_for_flip = 1;
     fd_set fds;
@@ -252,30 +262,8 @@ JNIEXPORT jlong JNICALL Java_jogamp_newt_driver_egl_gbm_WindowDriver_NextSwapSur
         ERR_PRINT("Failed to get a new framebuffer BO (1)\n");
         return 0;
     }
-#if 0
-    if( fbNext->x != x || fbNext->y != y ) {
-        // position changed, hard drmModeSetCrtc(..) w/o vsync
-        fbNext->x = x;
-        fbNext->y = y;
-
-        /**
-         * Set Mode 
-         *
-         * Fails with x/y != 0: -28 No space left on device
-         *   drmModeSetCrtc.0 failed to set mode: fd 26, crtc_id 0x27, fb_id 0x54, pos 10/10, conn_id 0x4d, curMode 1920x1080: -28 No space left on device
-         */
-        ret = drmModeSetCrtc(drmFd, crtc_id, fbNext->fb_id, fbNext->x, fbNext->y,
-                &connector_id, 1, drmMode);
-
-        if (ret) {
-            ERR_PRINT("drmModeSetCrtc.1 failed to set mode: fd %d, crtc_id 0x%x, fb_id 0x%x, pos %d/%d, conn_id 0x%x, curMode %s: %d %s\n", 
-                drmFd, crtc_id, fbNext->fb_id, jx, jy, connector_id, drmMode->name, ret, strerror(errno));
-            return 0;
-        }
-    } else
-#endif
     if( 0 != swapInterval) {
-        // same position, use vsync
+        // https://github.com/dvdhrm/docs/blob/master/drm-howto/modeset-vsync.c#L614
         ret = drmModePageFlip(drmFd, crtc_id, fbNext->fb_id,
                 DRM_MODE_PAGE_FLIP_EVENT, &waiting_for_flip);
         if (ret) {
@@ -286,9 +274,6 @@ JNIEXPORT jlong JNICALL Java_jogamp_newt_driver_egl_gbm_WindowDriver_NextSwapSur
 
         while (waiting_for_flip) {
             FD_ZERO(&fds);
-#if 0
-            FD_SET(0, &fds); // STDIN_FILENO: We don't want to listen to 
-#endif
             FD_SET(drmFd, &fds);
 
             ret = select(drmFd + 1, &fds, NULL, NULL, NULL);
@@ -298,10 +283,6 @@ JNIEXPORT jlong JNICALL Java_jogamp_newt_driver_egl_gbm_WindowDriver_NextSwapSur
             } else if (ret == 0) {
                 ERR_PRINT("drm.select: select timeout!\n");
                 return -1;
-#if 0
-            } else if (FD_ISSET(0, &fds)) {
-                DBG_PRINT("drm.select: stdin carriage return pressed!\n");
-#endif
             }
             drmHandleEvent(drmFd, &drm_event_ctx);
         }
@@ -315,8 +296,8 @@ JNIEXPORT jlong JNICALL Java_jogamp_newt_driver_egl_gbm_WindowDriver_NextSwapSur
 #ifdef VERBOSE_ON
     if( nextSwapVerboseOnce ) {
         nextSwapVerboseOnce = 0;
-        DBG_PRINT( "EGL_GBM.Window NextSwapSurface0 swapInterval %d, bo %p -> %p, fd %d, crtc_id 0x%x, fb_id 0x%x, pos %d/%d, conn_id 0x%x, curMode %s\n", 
-            swapInterval, lastBO, nextBO, drmFd, crtc_id, fbNext->fb_id, jx, jy, connector_id, drmMode->name);
+        DBG_PRINT( "EGL_GBM.Window NextSwapSurface0 swapInterval %d, bo %p -> %p, fd %d, crtc_id 0x%x, fb_id 0x%x, conn_id 0x%x, curMode %s\n", 
+            swapInterval, lastBO, nextBO, drmFd, crtc_id, fbNext->fb_id, connector_id, drmMode->name);
     }
 #endif
     return (jlong) (intptr_t) nextBO;