render/dmabuf: add dmabuf_import_sync_file

References: https://lore.kernel.org/dri-devel/20220506180216.2095060-1-jason@jlekstrand.net/

include/render/dmabuf.h

@@ -0,0 +1,26 @@
+#ifndef RENDER_DMABUF_H
+#define RENDER_DMABUF_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+// Copied from <linux/dma-buf.h> to avoid #ifdef soup
+#define DMA_BUF_SYNC_READ      (1 << 0)
+#define DMA_BUF_SYNC_WRITE     (2 << 0)
+#define DMA_BUF_SYNC_RW        (DMA_BUF_SYNC_READ | DMA_BUF_SYNC_WRITE)
+
+/**
+ * Check whether DMA-BUF import/export from/to sync_file is available.
+ *
+ * If this function returns true, dmabuf_import_sync_file() is supported.
+ */
+bool dmabuf_check_sync_file_import_export(void);
+
+/**
+ * Import a sync_file into a DMA-BUF with DMA_BUF_IOCTL_IMPORT_SYNC_FILE.
+ *
+ * This can be used to make explicit sync interoperate with implicit sync.
+ */
+bool dmabuf_import_sync_file(int dmabuf_fd, uint32_t flags, int sync_file_fd);
+
+#endif

render/dmabuf.c

@@ -3,6 +3,7 @@
 #include <unistd.h>
 #include <wlr/render/dmabuf.h>
 #include <wlr/util/log.h>
+#include "render/dmabuf.h"
 
 void wlr_dmabuf_attributes_finish(struct wlr_dmabuf_attributes *attribs) {
 	for (int i = 0; i < attribs->n_planes; ++i) {

render/dmabuf_fallback.c

@@ -0,0 +1,12 @@
+#include <wlr/util/log.h>
+
+#include "render/dmabuf.h"
+
+bool dmabuf_check_sync_file_import_export(void) {
+	return false;
+}
+
+bool dmabuf_import_sync_file(int dmabuf_fd, uint32_t flags, int sync_file_fd) {
+	wlr_log(WLR_ERROR, "DMA-BUF sync_file import IOCTL not available on this system");
+	return false;
+}

render/dmabuf_linux.c

@@ -0,0 +1,75 @@
+#include <linux/dma-buf.h>
+#include <linux/version.h>
+#include <stdlib.h>
+#include <sys/utsname.h>
+#include <wlr/util/log.h>
+#include <xf86drm.h>
+
+#include "render/dmabuf.h"
+
+bool dmabuf_check_sync_file_import_export(void) {
+	/* Unfortunately there's no better way to check the availability of the
+	 * IOCTL than to check the kernel version. See the discussion at:
+	 * https://lore.kernel.org/dri-devel/20220601161303.64797-1-contact@emersion.fr/
+	 */
+
+	struct utsname utsname = {0};
+	if (uname(&utsname) != 0) {
+		wlr_log_errno(WLR_ERROR, "uname failed");
+		return false;
+	}
+
+	if (strcmp(utsname.sysname, "Linux") != 0) {
+		return false;
+	}
+
+	// Trim release suffix if any, e.g. "-arch1-1"
+	for (size_t i = 0; utsname.release[i] != '\0'; i++) {
+		char ch = utsname.release[i];
+		if ((ch < '0' || ch > '9') && ch != '.') {
+			utsname.release[i] = '\0';
+			break;
+		}
+	}
+
+	char *rel = strtok(utsname.release, ".");
+	int major = atoi(rel);
+
+	int minor = 0;
+	rel = strtok(NULL, ".");
+	if (rel != NULL) {
+		minor = atoi(rel);
+	}
+
+	int patch = 0;
+	rel = strtok(NULL, ".");
+	if (rel != NULL) {
+		patch = atoi(rel);
+	}
+
+	return KERNEL_VERSION(major, minor, patch) >= KERNEL_VERSION(5, 20, 0);
+}
+
+// TODO: drop these definitions once widespread
+#if !defined(DMA_BUF_IOCTL_IMPORT_SYNC_FILE)
+
+struct dma_buf_import_sync_file {
+	__u32 flags;
+	__s32 fd;
+};
+
+#define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW(DMA_BUF_BASE, 3, struct dma_buf_import_sync_file)
+
+#endif
+
+bool dmabuf_import_sync_file(int dmabuf_fd, uint32_t flags, int sync_file_fd) {
+	struct dma_buf_import_sync_file data = {
+		.flags = flags,
+		.fd = sync_file_fd,
+	};
+	if (drmIoctl(dmabuf_fd, DMA_BUF_IOCTL_IMPORT_SYNC_FILE, &data) != 0) {
+		wlr_log_errno(WLR_ERROR, "drmIoctl(IMPORT_SYNC_FILE) failed");
+		return false;
+	}
+	return true;
+}

render/meson.build

@@ -14,6 +14,12 @@ wlr_files += files(
 	'wlr_texture.c',
 )
 
+if cc.has_header('linux/dma-buf.h') and target_machine.system() == 'linux'
+	wlr_files += files('dmabuf_linux.c')
+else
+	wlr_files += files('dmabuf_fallback.c')
+endif
+
 if 'gles2' in renderers or 'auto' in renderers
 	egl = dependency('egl', required: 'gles2' in renderers)
 	gbm = dependency('gbm', required: 'gles2' in renderers)