clients: add simple-v4l-dmabuf client

This client opens a V4L2 device, usually exposed as /dev/videoN, and
retrieves its frames as dmabuf for later import into the compositor.

It supports both single- and multi-planar devices, and any format
exposed by the V4L2 device the Wayland compositor accepts.

This client never changes the v4l2 settings, use `v4l2-ctl -c` if you
want to change those.

Signed-off-by: Emmanuel Gil Peyrot <emmanuel.peyrot@collabora.com>
Acked-by: Derek Foreman <derekf@osg.samsung.com>
Tested-by: Derek Foreman <derekf@osg.samsung.com>

Maniphest Tasks: T90

Differential Revision: https://phabricator.freedesktop.org/D339

4 files changed, 975 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
index 719054d7..dfbb4d30 100644
--- a/.gitignore
+++ b/.gitignore
@@ -67,6 +67,7 @@ weston-presentation-shm
 weston-resizor
 weston-scaler
 weston-simple-dmabuf-intel
+weston-simple-dmabuf-v4l
 weston-simple-egl
 weston-simple-shm
 weston-simple-touch
diff --git a/Makefile.am b/Makefile.am
index 1eb66aeb..623621da 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -538,6 +538,21 @@ weston_simple_dmabuf_intel_LDADD = $(SIMPLE_DMABUF_INTEL_CLIENT_LIBS) libshared.
 BUILT_SOURCES += protocol/linux-dmabuf-unstable-v1-client-protocol.h
 endif
 
+if BUILD_SIMPLE_DMABUF_V4L_CLIENT
+demo_clients += weston-simple-dmabuf-v4l
+weston_simple_dmabuf_v4l_SOURCES = clients/simple-dmabuf-v4l.c
+nodist_weston_simple_dmabuf_v4l_SOURCES =		\
+	protocol/xdg-shell-unstable-v5-protocol.c		\
+	protocol/xdg-shell-unstable-v5-client-protocol.h	\
+	protocol/fullscreen-shell-unstable-v1-protocol.c	\
+	protocol/fullscreen-shell-unstable-v1-client-protocol.h \
+	protocol/linux-dmabuf-unstable-v1-protocol.c \
+	protocol/linux-dmabuf-unstable-v1-client-protocol.h
+weston_simple_dmabuf_v4l_CFLAGS = $(AM_CFLAGS) $(SIMPLE_DMABUF_V4L_CLIENT_CFLAGS)
+weston_simple_dmabuf_v4l_LDADD = $(SIMPLE_DMABUF_V4L_CLIENT_LIBS) libshared.la
+BUILT_SOURCES += protocol/linux-dmabuf-unstable-v1-client-protocol.h
+endif
+
 noinst_LTLIBRARIES += libtoytoolkit.la
 
 libtoytoolkit_la_SOURCES =				\
diff --git a/clients/simple-dmabuf-v4l.c b/clients/simple-dmabuf-v4l.c
new file mode 100644
index 00000000..2334e099
--- /dev/null
+++ b/clients/simple-dmabuf-v4l.c
@@ -0,0 +1,945 @@
+/*
+ * Copyright © 2015 Collabora Ltd.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <assert.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <signal.h>
+#include <fcntl.h>
+
+#include <drm_fourcc.h>
+
+#include <stropts.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <linux/videodev2.h>
+#include <linux/input.h>
+
+#include <wayland-client.h>
+#include "xdg-shell-unstable-v5-client-protocol.h"
+#include "fullscreen-shell-unstable-v1-client-protocol.h"
+#include "linux-dmabuf-unstable-v1-client-protocol.h"
+
+#define CLEAR(x) memset(&(x), 0, sizeof(x))
+
+static int
+xioctl(int fh, int request, void *arg)
+{
+	int r;
+
+	do {
+		r = ioctl(fh, request, arg);
+	} while (r == -1 && errno == EINTR);
+
+	return r;
+}
+
+static uint32_t
+parse_format(const char fmt[4])
+{
+	return fourcc_code(fmt[0], fmt[1], fmt[2], fmt[3]);
+}
+
+static inline const char *
+dump_format(uint32_t format, char out[4])
+{
+#if BYTE_ORDER == BIG_ENDIAN
+	format = __builtin_bswap32(format);
+#endif
+	memcpy(out, &format, 4);
+	return out;
+}
+
+struct buffer_format {
+	int width;
+	int height;
+	enum v4l2_buf_type type;
+	uint32_t format;
+
+	unsigned num_planes;
+	unsigned strides[VIDEO_MAX_PLANES];
+};
+
+struct display {
+	struct wl_display *display;
+	struct wl_registry *registry;
+	struct wl_compositor *compositor;
+	struct wl_seat *seat;
+	struct wl_keyboard *keyboard;
+	struct xdg_shell *shell;
+	struct zwp_fullscreen_shell_v1 *fshell;
+	struct zwp_linux_dmabuf_v1 *dmabuf;
+	bool requested_format_found;
+
+	int v4l_fd;
+	struct buffer_format format;
+	uint32_t drm_format;
+};
+
+struct buffer {
+	struct wl_buffer *buffer;
+	struct display *display;
+	int busy;
+	int index;
+
+	int dmabuf_fds[VIDEO_MAX_PLANES];
+	int data_offsets[VIDEO_MAX_PLANES];
+};
+
+#define NUM_BUFFERS 3
+
+struct window {
+	struct display *display;
+	struct wl_surface *surface;
+	struct xdg_surface *xdg_surface;
+	struct buffer buffers[NUM_BUFFERS];
+	struct wl_callback *callback;
+};
+
+static bool running = true;
+
+static int
+queue(struct display *display, struct buffer *buffer)
+{
+	struct v4l2_buffer buf;
+	struct v4l2_plane planes[VIDEO_MAX_PLANES];
+	unsigned i;
+
+	CLEAR(buf);
+	buf.type = display->format.type;
+	buf.memory = V4L2_MEMORY_MMAP;
+	buf.index = buffer->index;
+
+	if (display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) {
+		CLEAR(planes);
+		buf.length = VIDEO_MAX_PLANES;
+		buf.m.planes = planes;
+	}
+
+	if (xioctl(display->v4l_fd, VIDIOC_QUERYBUF, &buf) == -1) {
+		perror("VIDIOC_QUERYBUF");
+		return 0;
+	}
+
+	if (xioctl(display->v4l_fd, VIDIOC_QBUF, &buf) == -1) {
+		perror("VIDIOC_QBUF");
+		return 0;
+	}
+
+	if (display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) {
+		if (display->format.num_planes != buf.length) {
+			fprintf(stderr, "Wrong number of planes returned by "
+			                "QUERYBUF\n");
+			return 0;
+		}
+
+		for (i = 0; i < buf.length; ++i)
+			buffer->data_offsets[i] = buf.m.planes[i].data_offset;
+	}
+
+	return 1;
+}
+
+static void
+buffer_release(void *data, struct wl_buffer *buffer)
+{
+	struct buffer *mybuf = data;
+
+	mybuf->busy = 0;
+
+	if (!queue(mybuf->display, mybuf))
+		running = false;
+}
+
+static const struct wl_buffer_listener buffer_listener = {
+	buffer_release
+};
+
+static unsigned int
+set_format(struct display *display, uint32_t format)
+{
+	struct v4l2_format fmt;
+	char buf[4];
+
+	CLEAR(fmt);
+
+	fmt.type = display->format.type;
+
+	if (xioctl(display->v4l_fd, VIDIOC_G_FMT, &fmt) == -1) {
+		perror("VIDIOC_G_FMT");
+		return 0;
+	}
+
+	/* No need to set the format if it already is the one we want */
+	if (display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE &&
+	    fmt.fmt.pix.pixelformat == format)
+		return 1;
+	if (display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE &&
+	    fmt.fmt.pix_mp.pixelformat == format)
+		return fmt.fmt.pix_mp.num_planes;
+
+	if (display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
+		fmt.fmt.pix.pixelformat = format;
+	else
+		fmt.fmt.pix_mp.pixelformat = format;
+
+	if (xioctl(display->v4l_fd, VIDIOC_S_FMT, &fmt) == -1) {
+		perror("VIDIOC_S_FMT");
+		return 0;
+	}
+
+	if ((display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE &&
+	     fmt.fmt.pix.pixelformat != format) ||
+	    (display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE &&
+	     fmt.fmt.pix_mp.pixelformat != format)) {
+		fprintf(stderr, "Failed to set format to %.4s\n",
+		        dump_format(format, buf));
+		return 0;
+	}
+
+	if (display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
+		return fmt.fmt.pix_mp.num_planes;
+
+	return 1;
+}
+
+static int
+v4l_connect(struct display *display, const char *dev_name)
+{
+	struct v4l2_capability cap;
+	struct v4l2_requestbuffers req;
+	unsigned int num_planes;
+
+	display->v4l_fd = open(dev_name, O_RDWR);
+	if (display->v4l_fd < 0) {
+		perror(dev_name);
+		return 0;
+	}
+
+	if (xioctl(display->v4l_fd, VIDIOC_QUERYCAP, &cap) == -1) {
+		if (errno == EINVAL) {
+			fprintf(stderr, "%s is no V4L2 device\n", dev_name);
+		} else {
+			perror("VIDIOC_QUERYCAP");
+		}
+		return 0;
+	}
+
+	if (cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)
+		display->format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+	else if (cap.capabilities & V4L2_CAP_VIDEO_CAPTURE_MPLANE)
+		display->format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
+	else {
+		fprintf(stderr, "%s is no video capture device\n", dev_name);
+		return 0;
+	}
+
+	if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
+		fprintf(stderr, "%s does not support dmabuf i/o\n", dev_name);
+		return 0;
+	}
+
+	/* Select video input, video standard and tune here */
+
+	num_planes = set_format(display, display->format.format);
+	if (num_planes < 1)
+		return 0;
+
+	CLEAR(req);
+
+	req.type = display->format.type;
+	req.memory = V4L2_MEMORY_MMAP;
+	req.count = NUM_BUFFERS * num_planes;
+
+	if (xioctl(display->v4l_fd, VIDIOC_REQBUFS, &req) == -1) {
+		if (errno == EINVAL) {
+			fprintf(stderr, "%s does not support dmabuf\n",
+			        dev_name);
+		} else {
+			perror("VIDIOC_REQBUFS");
+		}
+		return 0;
+	}
+
+	if (req.count < NUM_BUFFERS * num_planes) {
+		fprintf(stderr, "Insufficient buffer memory on %s\n", dev_name);
+		return 0;
+	}
+
+	printf("Created %d buffers\n", req.count);
+
+	return 1;
+}
+
+static void
+v4l_shutdown(struct display *display)
+{
+	close(display->v4l_fd);
+}
+
+static void
+create_succeeded(void *data,
+		 struct zwp_linux_buffer_params_v1 *params,
+		 struct wl_buffer *new_buffer)
+{
+	struct buffer *buffer = data;
+	unsigned i;
+
+	buffer->buffer = new_buffer;
+	wl_buffer_add_listener(buffer->buffer, &buffer_listener, buffer);
+
+	zwp_linux_buffer_params_v1_destroy(params);
+
+	for (i = 0; i < buffer->display->format.num_planes; ++i)
+		close(buffer->dmabuf_fds[i]);
+}
+
+static void
+create_failed(void *data, struct zwp_linux_buffer_params_v1 *params)
+{
+	struct buffer *buffer = data;
+	unsigned i;
+
+	buffer->buffer = NULL;
+
+	zwp_linux_buffer_params_v1_destroy(params);
+
+	for (i = 0; i < buffer->display->format.num_planes; ++i)
+		close(buffer->dmabuf_fds[i]);
+
+	running = false;
+
+	fprintf(stderr, "Error: zwp_linux_buffer_params.create failed.\n");
+}
+
+static const struct zwp_linux_buffer_params_v1_listener params_listener = {
+	create_succeeded,
+	create_failed
+};
+
+static void
+create_dmabuf_buffer(struct display *display, struct buffer *buffer)
+{
+	struct zwp_linux_buffer_params_v1 *params;
+	uint64_t modifier;
+	uint32_t flags;
+	unsigned i;
+
+	modifier = 0;
+	flags = ZWP_LINUX_BUFFER_PARAMS_V1_FLAGS_Y_INVERT;
+
+	params = zwp_linux_dmabuf_v1_create_params(display->dmabuf);
+	for (i = 0; i < display->format.num_planes; ++i)
+		zwp_linux_buffer_params_v1_add(params,
+		                               buffer->dmabuf_fds[i],
+		                               i, /* plane_idx */
+		                               buffer->data_offsets[i], /* offset */
+		                               display->format.strides[i],
+		                               modifier >> 32,
+		                               modifier & 0xffffffff);
+	zwp_linux_buffer_params_v1_add_listener(params, &params_listener,
+	                                        buffer);
+	zwp_linux_buffer_params_v1_create(params,
+	                                  display->format.width,
+	                                  display->format.height,
+	                                  display->drm_format,
+	                                  flags);
+}
+
+static int
+buffer_export(struct display *display, int index, int dmafd[])
+{
+	struct v4l2_exportbuffer expbuf;
+	unsigned i;
+
+	CLEAR(expbuf);
+
+	for (i = 0; i < display->format.num_planes; ++i) {
+		expbuf.type = display->format.type;
+		expbuf.index = index;
+		expbuf.plane = i;
+		if (xioctl(display->v4l_fd, VIDIOC_EXPBUF, &expbuf) == -1) {
+			perror("VIDIOC_EXPBUF");
+			while (i)
+				close(dmafd[--i]);
+			return 0;
+		}
+		dmafd[i] = expbuf.fd;
+	}
+
+	return 1;
+}
+
+static int
+queue_initial_buffers(struct display *display,
+                      struct buffer buffers[NUM_BUFFERS])
+{
+	struct buffer *buffer;
+	int index;
+
+	for (index = 0; index < NUM_BUFFERS; ++index) {
+		buffer = &buffers[index];
+		buffer->display = display;
+		buffer->index = index;
+
+		if (!queue(display, buffer)) {
+			fprintf(stderr, "Failed to queue buffer\n");
+			return 0;
+		}
+
+		assert(!buffer->buffer);
+		if (!buffer_export(display, index, buffer->dmabuf_fds))
+			return 0;
+
+		create_dmabuf_buffer(display, buffer);
+	}
+
+	return 1;
+}
+
+static int
+dequeue(struct display *display)
+{
+	struct v4l2_buffer buf;
+	struct v4l2_plane planes[VIDEO_MAX_PLANES];
+
+	CLEAR(buf);
+	buf.type = display->format.type;
+	buf.memory = V4L2_MEMORY_MMAP;
+	buf.length = VIDEO_MAX_PLANES;
+	buf.m.planes = planes;
+
+	/* This ioctl is blocking until a buffer is ready to be displayed */
+	if (xioctl(display->v4l_fd, VIDIOC_DQBUF, &buf) == -1) {
+		perror("VIDIOC_DQBUF");
+		return -1;
+	}
+
+	assert(buf.flags & V4L2_BUF_FLAG_DONE);
+
+	return buf.index;
+}
+
+static int
+fill_buffer_format(struct display *display)
+{
+	struct v4l2_format fmt;
+	struct v4l2_pix_format *pix;
+	struct v4l2_pix_format_mplane *pix_mp;
+	int i;
+	char buf[4];
+
+	CLEAR(fmt);
+	fmt.type = display->format.type;
+
+	/* Preserve original settings as set by v4l2-ctl for example */
+	if (xioctl(display->v4l_fd, VIDIOC_G_FMT, &fmt) == -1) {
+		perror("VIDIOC_G_FMT");
+		return 0;
+	}
+
+	if (display->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
+		pix = &fmt.fmt.pix;
+
+		printf("%d×%d, %.4s\n", pix->width, pix->height,
+		       dump_format(pix->pixelformat, buf));
+
+		display->format.num_planes = 1;
+		display->format.width = pix->width;
+		display->format.height = pix->height;
+		display->format.strides[0] = pix->bytesperline;
+	} else {
+		pix_mp = &fmt.fmt.pix_mp;
+
+		display->format.num_planes = pix_mp->num_planes;
+		display->format.width = pix_mp->width;
+		display->format.height = pix_mp->height;
+
+		for (i = 0; i < pix_mp->num_planes; ++i)
+			display->format.strides[i] = pix_mp->plane_fmt[i].bytesperline;
+
+		printf("%d×%d, %.4s, %d planes\n",
+		       pix_mp->width, pix_mp->height,
+		       dump_format(pix_mp->pixelformat, buf),
+		       pix_mp->num_planes);
+	}
+
+	return 1;
+}
+
+static int
+v4l_init(struct display *display, struct buffer buffers[NUM_BUFFERS]) {
+	if (!fill_buffer_format(display)) {
+		fprintf(stderr, "Failed to fill buffer format\n");
+		return 0;
+	}
+
+	if (!queue_initial_buffers(display, buffers)) {
+		fprintf(stderr, "Failed to queue initial buffers\n");
+		return 0;
+	}
+
+	return 1;
+}
+
+static int
+start_capture(struct display *display)
+{
+	int type = display->format.type;
+
+	if (xioctl(display->v4l_fd, VIDIOC_STREAMON, &type) == -1) {
+		perror("VIDIOC_STREAMON");
+		return 0;
+	}
+
+	return 1;
+}
+
+static void
+handle_configure(void *data, struct xdg_surface *surface,
+		 int32_t width, int32_t height,
+		 struct wl_array *states, uint32_t serial)
+{
+}
+
+static void
+handle_delete(void *data, struct xdg_surface *xdg_surface)
+{
+	running = false;
+}
+
+static const struct xdg_surface_listener xdg_surface_listener = {
+	handle_configure,
+	handle_delete,
+};
+
+static struct window *
+create_window(struct display *display)
+{
+	struct window *window;
+
+	window = calloc(1, sizeof *window);
+	if (!window)
+		return NULL;
+
+	window->callback = NULL;
+	window->display = display;
+	window->surface = wl_compositor_create_surface(display->compositor);
+
+	if (display->shell) {
+		window->xdg_surface =
+			xdg_shell_get_xdg_surface(display->shell,
+			                          window->surface);
+
+		assert(window->xdg_surface);
+
+		xdg_surface_add_listener(window->xdg_surface,
+		                         &xdg_surface_listener, window);
+
+		xdg_surface_set_title(window->xdg_surface, "simple-dmabuf-v4l");
+	} else if (display->fshell) {
+		zwp_fullscreen_shell_v1_present_surface(display->fshell,
+		                                        window->surface,
+		                                        ZWP_FULLSCREEN_SHELL_V1_PRESENT_METHOD_DEFAULT,
+		                                        NULL);
+	} else {
+		assert(0);
+	}
+
+	return window;
+}
+
+static void
+destroy_window(struct window *window)
+{
+	int i;
+	unsigned j;
+
+	if (window->callback)
+		wl_callback_destroy(window->callback);
+
+	if (window->xdg_surface)
+		xdg_surface_destroy(window->xdg_surface);
+	wl_surface_destroy(window->surface);
+
+	for (i = 0; i < NUM_BUFFERS; i++) {
+		if (!window->buffers[i].buffer)
+			continue;
+
+		wl_buffer_destroy(window->buffers[i].buffer);
+		for (j = 0; j < window->display->format.num_planes; ++j)
+			close(window->buffers[i].dmabuf_fds[j]);
+	}
+
+	v4l_shutdown(window->display);
+
+	free(window);
+}
+
+static const struct wl_callback_listener frame_listener;
+
+static void
+redraw(void *data, struct wl_callback *callback, uint32_t time)
+{
+	struct window *window = data;
+	struct buffer *buffer;
+	int index, num_busy = 0;
+
+	/* Check for a deadlock situation where we would block forever trying
+	 * to dequeue a buffer while all of them are locked by the compositor.
+	 */
+	for (index = 0; index < NUM_BUFFERS; ++index)
+		if (window->buffers[index].busy)
+			++num_busy;
+
+	/* A robust application would just postpone redraw until it has queued
+	 * a buffer.
+	 */
+	assert(num_busy < NUM_BUFFERS);
+
+	index = dequeue(window->display);
+	if (index < 0) {
+		/* We couldn’t get any buffer out of the camera, exiting. */
+		running = false;
+		return;
+	}
+
+	buffer = &window->buffers[index];
+	assert(!buffer->busy);
+
+	wl_surface_attach(window->surface, buffer->buffer, 0, 0);
+	wl_surface_damage(window->surface, 0, 0,
+	                  window->display->format.width,
+	                  window->display->format.height);
+
+	if (callback)
+		wl_callback_destroy(callback);
+
+	window->callback = wl_surface_frame(window->surface);
+	wl_callback_add_listener(window->callback, &frame_listener, window);
+	wl_surface_commit(window->surface);
+	buffer->busy = 1;
+}
+
+static const struct wl_callback_listener frame_listener = {
+	redraw
+};
+
+static void
+dmabuf_format(void *data, struct zwp_linux_dmabuf_v1 *zwp_linux_dmabuf,
+              uint32_t format)
+{
+	struct display *d = data;
+
+	if (format == d->drm_format)
+		d->requested_format_found = true;
+}
+
+static const struct zwp_linux_dmabuf_v1_listener dmabuf_listener = {
+	dmabuf_format
+};
+
+static void
+keyboard_handle_keymap(void *data, struct wl_keyboard *keyboard,
+                       uint32_t format, int fd, uint32_t size)
+{
+	/* Just so we don’t leak the keymap fd */
+	close(fd);
+}
+
+static void
+keyboard_handle_enter(void *data, struct wl_keyboard *keyboard,
+                      uint32_t serial, struct wl_surface *surface,
+                      struct wl_array *keys)
+{
+}
+
+static void
+keyboard_handle_leave(void *data, struct wl_keyboard *keyboard,
+                      uint32_t serial, struct wl_surface *surface)
+{
+}
+
+static void
+keyboard_handle_key(void *data, struct wl_keyboard *keyboard,
+                    uint32_t serial, uint32_t time, uint32_t key,
+                    uint32_t state)
+{
+	struct display *d = data;
+
+	if (!d->shell)
+		return;
+
+	if (key == KEY_ESC && state)
+		running = false;
+}
+
+static void
+keyboard_handle_modifiers(void *data, struct wl_keyboard *keyboard,
+                          uint32_t serial, uint32_t mods_depressed,
+                          uint32_t mods_latched, uint32_t mods_locked,
+                          uint32_t group)
+{
+}
+
+static const struct wl_keyboard_listener keyboard_listener = {
+	keyboard_handle_keymap,
+	keyboard_handle_enter,
+	keyboard_handle_leave,
+	keyboard_handle_key,
+	keyboard_handle_modifiers,
+};
+
+static void
+seat_handle_capabilities(void *data, struct wl_seat *seat,
+                         enum wl_seat_capability caps)
+{
+	struct display *d = data;
+
+	if ((caps & WL_SEAT_CAPABILITY_KEYBOARD) && !d->keyboard) {
+		d->keyboard = wl_seat_get_keyboard(seat);
+		wl_keyboard_add_listener(d->keyboard, &keyboard_listener, d);
+	} else if (!(caps & WL_SEAT_CAPABILITY_KEYBOARD) && d->keyboard) {
+		wl_keyboard_destroy(d->keyboard);
+		d->keyboard = NULL;
+	}
+}
+
+static const struct wl_seat_listener seat_listener = {
+	seat_handle_capabilities,
+};
+
+static void
+xdg_shell_ping(void *data, struct xdg_shell *shell, uint32_t serial)
+{
+	xdg_shell_pong(shell, serial);
+}
+
+static const struct xdg_shell_listener xdg_shell_listener = {
+	xdg_shell_ping,
+};
+
+#define XDG_VERSION 5 /* The version of xdg-shell that we implement */
+#ifdef static_assert
+static_assert(XDG_VERSION == XDG_SHELL_VERSION_CURRENT,
+              "Interface version doesn't match implementation version");
+#endif
+
+static void
+registry_handle_global(void *data, struct wl_registry *registry,
+                       uint32_t id, const char *interface, uint32_t version)
+{
+	struct display *d = data;
+
+	if (strcmp(interface, "wl_compositor") == 0) {
+		d->compositor =
+			wl_registry_bind(registry,
+			                 id, &wl_compositor_interface, 1);
+	} else if (strcmp(interface, "wl_seat") == 0) {
+		d->seat = wl_registry_bind(registry,
+		                           id, &wl_seat_interface, 1);
+		wl_seat_add_listener(d->seat, &seat_listener, d);
+	} else if (strcmp(interface, "xdg_shell") == 0) {
+		d->shell = wl_registry_bind(registry,
+		                            id, &xdg_shell_interface, 1);
+		xdg_shell_use_unstable_version(d->shell, XDG_VERSION);
+		xdg_shell_add_listener(d->shell, &xdg_shell_listener, d);
+	} else if (strcmp(interface, "zwp_fullscreen_shell_v1") == 0) {
+		d->fshell = wl_registry_bind(registry,
+		                             id, &zwp_fullscreen_shell_v1_interface,
+		                             1);
+	} else if (strcmp(interface, "zwp_linux_dmabuf_v1") == 0) {
+		d->dmabuf = wl_registry_bind(registry,
+		                             id, &zwp_linux_dmabuf_v1_interface,
+		                             1);
+		zwp_linux_dmabuf_v1_add_listener(d->dmabuf, &dmabuf_listener,
+		                                 d);
+	}
+}
+
+static void
+registry_handle_global_remove(void *data, struct wl_registry *registry,
+                              uint32_t name)
+{
+}
+
+static const struct wl_registry_listener registry_listener = {
+	registry_handle_global,
+	registry_handle_global_remove
+};
+
+static struct display *
+create_display(uint32_t requested_format)
+{
+	struct display *display;
+
+	display = malloc(sizeof *display);
+	if (display == NULL) {
+		fprintf(stderr, "out of memory\n");
+		exit(1);
+	}
+	display->display = wl_display_connect(NULL);
+	assert(display->display);
+
+	display->drm_format = requested_format;
+
+	display->registry = wl_display_get_registry(display->display);
+	wl_registry_add_listener(display->registry,
+	                         &registry_listener, display);
+	wl_display_roundtrip(display->display);
+	if (display->dmabuf == NULL) {
+		fprintf(stderr, "No zwp_linux_dmabuf global\n");
+		exit(1);
+	}
+
+	wl_display_roundtrip(display->display);
+
+	/* XXX: fake, because the compositor does not yet advertise anything */
+	display->requested_format_found = true;
+
+	if (!display->requested_format_found) {
+		fprintf(stderr, "DRM_FORMAT_YUYV not available\n");
+		exit(1);
+	}
+
+	return display;
+}
+
+static void
+destroy_display(struct display *display)
+{
+	if (display->dmabuf)
+		zwp_linux_dmabuf_v1_destroy(display->dmabuf);
+
+	if (display->shell)
+		xdg_shell_destroy(display->shell);
+
+	if (display->fshell)
+		zwp_fullscreen_shell_v1_release(display->fshell);
+
+	if (display->compositor)
+		wl_compositor_destroy(display->compositor);
+
+	wl_registry_destroy(display->registry);
+	wl_display_flush(display->display);
+	wl_display_disconnect(display->display);
+	free(display);
+}
+
+static void
+usage(const char *argv0)
+{
+	printf("Usage: %s [V4L2 device] [V4L2 format] [DRM format]\n"
+	       "\n"
+	       "The default V4L2 device is /dev/video0\n"
+	       "\n"
+	       "Both formats are FOURCC values (see http://fourcc.org/)\n"
+	       "V4L2 formats are defined in <linux/videodev2.h>\n"
+	       "DRM formats are defined in <libdrm/drm_fourcc.h>\n"
+	       "The default for both formats is YUYV.\n"
+	       "If the V4L2 and DRM formats differ, the data is simply "
+	       "reinterpreted rather than converted.\n", argv0);
+	exit(0);
+}
+
+static void
+signal_int(int signum)
+{
+	running = false;
+}
+
+int
+main(int argc, char **argv)
+{
+	struct sigaction sigint;
+	struct display *display;
+	struct window *window;
+	const char *v4l_device;
+	uint32_t v4l_format, drm_format;
+	int ret = 0;
+
+	if (argc < 2) {
+		v4l_device = "/dev/video0";
+	} else if (!strcmp(argv[1], "--help")) {
+		usage(argv[0]);
+	} else {
+		v4l_device = argv[1];
+	}
+
+	if (argc < 3)
+		v4l_format = parse_format("YUYV");
+	else
+		v4l_format = parse_format(argv[2]);
+
+	if (argc < 4)
+		drm_format = v4l_format;
+	else
+		drm_format = parse_format(argv[3]);
+
+	display = create_display(drm_format);
+	display->format.format = v4l_format;
+
+	window = create_window(display);
+	if (!window)
+		return 1;
+
+	if (!v4l_connect(display, v4l_device))
+		return 1;
+
+	if (!v4l_init(display, window->buffers))
+		return 1;
+
+	sigint.sa_handler = signal_int;
+	sigemptyset(&sigint.sa_mask);
+	sigint.sa_flags = SA_RESETHAND;
+	sigaction(SIGINT, &sigint, NULL);
+
+	/* Here we retrieve the linux-dmabuf objects, or error */
+	wl_display_roundtrip(display->display);
+
+	/* In case of error, running will be 0 */
+	if (!running)
+		return 1;
+
+	/* We got all of our buffers, we can start the capture! */
+	if (!start_capture(display))
+		return 1;
+
+	redraw(window, NULL, 0);
+
+	while (running && ret != -1)
+		ret = wl_display_dispatch(display->display);
+
+	fprintf(stderr, "simple-dmabuf-v4l exiting\n");
+	destroy_window(window);
+	destroy_display(display);
+
+	return 0;
+}
diff --git a/configure.ac b/configure.ac
index 24a9de22..97cbfe51 100644
--- a/configure.ac
+++ b/configure.ac
@@ -356,6 +356,20 @@ if ! test "x$enable_simple_dmabuf_intel_client" = "xno"; then
 fi
 AM_CONDITIONAL(BUILD_SIMPLE_DMABUF_INTEL_CLIENT, test "x$enable_simple_dmabuf_intel_client" = "xyes")
 
+AC_ARG_ENABLE(simple-dmabuf-v4l-client,
+              AS_HELP_STRING([--disable-simple-dmabuf-v4l-client],
+                             [do not build the simple dmabuf v4l client]),,
+              enable_simple_dmabuf_v4l_client="auto")
+if ! test "x$enable_simple_dmabuf_v4l_client" = "xno"; then
+  PKG_CHECK_MODULES(SIMPLE_DMABUF_V4L_CLIENT, [wayland-client libdrm],
+		    have_simple_dmabuf_v4l_client=yes, have_simple_dmabuf_v4l_client=no)
+  if test "x$have_simple_dmabuf_v4l_client" = "xno" -a "x$enable_simple_dmabuf_v4l_client" = "xyes"; then
+    AC_MSG_ERROR([V4L dmabuf client explicitly enabled, but libdrm couldn't be found])
+  fi
+  enable_simple_dmabuf_v4l_client="$have_simple_dmabuf_v4l_client"
+fi
+AM_CONDITIONAL(BUILD_SIMPLE_DMABUF_V4L_CLIENT, test "x$enable_simple_dmabuf_v4l_client" = "xyes")
+
 AC_ARG_ENABLE(clients, [  --enable-clients],, enable_clients=yes)
 AM_CONDITIONAL(BUILD_CLIENTS, test x$enable_clients = xyes)
 if test x$enable_clients = xyes; then