pipewire/spa/plugins/v4l2/v4l2-udev.c

/* Spa V4l2 udev monitor */
/* SPDX-FileCopyrightText: Copyright © 2018 Wim Taymans */
/* SPDX-License-Identifier: MIT */

#include <stddef.h>
#include <stdio.h>
#include <unistd.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/inotify.h>
#include <fcntl.h>

#include <libudev.h>

#include <spa/support/log.h>
#include <spa/utils/type.h>
#include <spa/utils/keys.h>
#include <spa/utils/names.h>
#include <spa/utils/result.h>
#include <spa/utils/string.h>
#include <spa/support/loop.h>
#include <spa/support/plugin.h>
#include <spa/monitor/device.h>
#include <spa/monitor/utils.h>

#include "config.h"
#include "v4l2.h"

#ifdef HAVE_SYSTEMD
#include <systemd/sd-login.h>
#endif

#define MAX_DEVICES	64

enum action {
	ACTION_CHANGE,
	ACTION_REMOVE,
};

struct device {
	uint32_t id;
	struct udev_device *dev;
	int inotify_wd;
	unsigned int accessible:1;
	unsigned int emitted:1;
};

struct impl {
	struct spa_handle handle;
	struct spa_device device;

	struct spa_log *log;
	struct spa_loop *main_loop;

	struct spa_hook_list hooks;

	uint64_t info_all;
	struct spa_device_info info;

	struct udev *udev;
	struct udev_monitor *umonitor;

	struct device devices[MAX_DEVICES];
        uint32_t n_devices;

	struct spa_source source;
	struct spa_source notify;
#ifdef HAVE_SYSTEMD
	struct spa_source logind;
	sd_login_monitor *logind_monitor;
#endif
};

static int impl_udev_open(struct impl *this)
{
	if (this->udev == NULL) {
		this->udev = udev_new();
		if (this->udev == NULL)
			return -ENOMEM;
	}
	return 0;
}

static int impl_udev_close(struct impl *this)
{
	if (this->udev != NULL)
		udev_unref(this->udev);
	this->udev = NULL;
	return 0;
}

static void start_watching_device(struct impl *this, struct device *device)
{
	if (this->notify.fd < 0 || device->inotify_wd >= 0)
		return;

	char path[64];
	snprintf(path, sizeof(path), "/dev/video%" PRIu32, device->id);

	device->inotify_wd = inotify_add_watch(this->notify.fd, path, IN_ATTRIB);
}

static void stop_watching_device(struct impl *this, struct device *device)
{
	if (device->inotify_wd < 0)
		return;

	spa_assert(this->notify.fd >= 0);

	inotify_rm_watch(this->notify.fd, device->inotify_wd);
	device->inotify_wd = -1;
}

static struct device *add_device(struct impl *this, uint32_t id, struct udev_device *dev)
{
	struct device *device;

	if (this->n_devices >= MAX_DEVICES)
		return NULL;
	device = &this->devices[this->n_devices++];
	spa_zero(*device);
	device->id = id;
	udev_device_ref(dev);
	device->dev = dev;
	device->inotify_wd = -1;

	start_watching_device(this, device);

	return device;
}

static struct device *find_device(struct impl *this, uint32_t id)
{
	uint32_t i;
	for (i = 0; i < this->n_devices; i++) {
		if (this->devices[i].id == id)
			return &this->devices[i];
	}
	return NULL;
}

static void remove_device(struct impl *this, struct device *device)
{
	device->dev = udev_device_unref(device->dev);
	stop_watching_device(this, device);
	*device = this->devices[--this->n_devices];
}

static void clear_devices(struct impl *this)
{
	while (this->n_devices > 0)
		remove_device(this, &this->devices[0]);
}

static uint32_t get_device_id(struct impl *this, struct udev_device *dev)
{
	const char *str;

	if ((str = udev_device_get_devnode(dev)) == NULL)
		return SPA_ID_INVALID;

        if (!(str = strrchr(str, '/')))
                return SPA_ID_INVALID;

        if (strlen(str) <= 6 || strncmp(str, "/video", 6) != 0)
                return SPA_ID_INVALID;

	return atoi(str + 6);
}

static int dehex(char x)
{
	if (x >= '0' && x <= '9')
		return x - '0';
	if (x >= 'A' && x <= 'F')
		return x - 'A' + 10;
	if (x >= 'a' && x <= 'f')
		return x - 'a' + 10;
	return -1;
}

static void unescape(const char *src, char *dst)
{
	const char *s;
	char *d;
	int h1 = 0, h2 = 0;
	enum { TEXT, BACKSLASH, EX, FIRST } state = TEXT;

	for (s = src, d = dst; *s; s++) {
		switch (state) {
		case TEXT:
			if (*s == '\\')
				state = BACKSLASH;
			else
				*(d++) = *s;
			break;

		case BACKSLASH:
			if (*s == 'x')
				state = EX;
			else {
				*(d++) = '\\';
				*(d++) = *s;
				state = TEXT;
			}
			break;

		case EX:
			h1 = dehex(*s);
			if (h1 < 0) {
				*(d++) = '\\';
				*(d++) = 'x';
				*(d++) = *s;
				state = TEXT;
			} else
				state = FIRST;
			break;

		case FIRST:
			h2 = dehex(*s);
			if (h2 < 0) {
				*(d++) = '\\';
				*(d++) = 'x';
				*(d++) = *(s-1);
				*(d++) = *s;
			} else
				*(d++) = (char) (h1 << 4) | h2;
			state = TEXT;
			break;
		}
	}
	switch (state) {
	case TEXT:
		break;
	case BACKSLASH:
		*(d++) = '\\';
		break;
	case EX:
		*(d++) = '\\';
		*(d++) = 'x';
		break;
	case FIRST:
		*(d++) = '\\';
		*(d++) = 'x';
		*(d++) = *(s-1);
		break;
	}
	*d = 0;
}

static int emit_object_info(struct impl *this, struct device *device)
{
	struct spa_device_object_info info;
	uint32_t id = device->id;
	struct udev_device *dev = device->dev;
	const char *str;
	struct spa_dict_item items[21];
	uint32_t n_items = 0;
	char devnum[32];

	info = SPA_DEVICE_OBJECT_INFO_INIT();

	info.type = SPA_TYPE_INTERFACE_Device;
	info.factory_name = SPA_NAME_API_V4L2_DEVICE;
	info.change_mask = SPA_DEVICE_OBJECT_CHANGE_MASK_FLAGS |
		SPA_DEVICE_OBJECT_CHANGE_MASK_PROPS;
	info.flags = 0;

	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_ENUM_API,"udev");
	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_API, "v4l2");
	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_MEDIA_CLASS, "Video/Device");

	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_API_V4L2_PATH, udev_device_get_devnode(dev));
	snprintf(devnum, sizeof(devnum), "%" PRId64, (int64_t)udev_device_get_devnum(dev));
	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_DEVIDS, devnum);

	if ((str = udev_device_get_property_value(dev, "USEC_INITIALIZED")) && *str)
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_PLUGGED_USEC, str);

	str = udev_device_get_property_value(dev, "ID_PATH");
	if (!(str && *str))
		str = udev_device_get_syspath(dev);
	if (str && *str) {
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_BUS_PATH, str);
	}
	if ((str = udev_device_get_devpath(dev)) && *str) {
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_SYSFS_PATH, str);
	}
	if ((str = udev_device_get_property_value(dev, "ID_ID")) && *str) {
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_BUS_ID, str);
	}
	if ((str = udev_device_get_property_value(dev, "ID_BUS")) && *str) {
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_BUS, str);
	}
	if ((str = udev_device_get_property_value(dev, "SUBSYSTEM")) && *str) {
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_SUBSYSTEM, str);
	}
	if ((str = udev_device_get_property_value(dev, "ID_VENDOR_ID")) && *str) {
		int32_t val;
		if (spa_atoi32(str, &val, 16)) {
			char *dec = alloca(12); /* 0xffff is max */
			snprintf(dec, 12, "0x%04x", val);
			items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_VENDOR_ID, dec);
		}
	}
	str = udev_device_get_property_value(dev, "ID_VENDOR_FROM_DATABASE");
	if (!(str && *str)) {
		str = udev_device_get_property_value(dev, "ID_VENDOR_ENC");
		if (!(str && *str)) {
			str = udev_device_get_property_value(dev, "ID_VENDOR");
		} else {
			char *t = alloca(strlen(str) + 1);
			unescape(str, t);
			str = t;
		}
	}
	if (str && *str) {
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_VENDOR_NAME, str);
	}
	if ((str = udev_device_get_property_value(dev, "ID_MODEL_ID")) && *str) {
		int32_t val;
		if (spa_atoi32(str, &val, 16)) {
			char *dec = alloca(12); /* 0xffff is max */
			snprintf(dec, 12, "0x%04x", val);
			items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_PRODUCT_ID, dec);
		}
	}

	str = udev_device_get_property_value(dev, "ID_MODEL_FROM_DATABASE");
	if (!(str && *str)) {
		str = udev_device_get_property_value(dev, "ID_MODEL_ENC");
		if (!(str && *str)) {
			str = udev_device_get_property_value(dev, "ID_MODEL");
			if (!(str && *str))
				str = udev_device_get_property_value(dev, "ID_V4L_PRODUCT");
		} else {
			char *t = alloca(strlen(str) + 1);
			unescape(str, t);
			str = t;
		}
	}
	if (str && *str)
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_PRODUCT_NAME, str);

	if ((str = udev_device_get_property_value(dev, "ID_SERIAL")) && *str) {
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_SERIAL, str);
	}
	if ((str = udev_device_get_property_value(dev, "ID_V4L_CAPABILITIES")) && *str) {
		items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_CAPABILITIES, str);
	}
        info.props = &SPA_DICT_INIT(items, n_items);
        spa_device_emit_object_info(&this->hooks, id, &info);
	device->emitted = true;

	return 1;
}

static bool check_access(struct impl *this, struct device *device)
{
	char path[128];

	snprintf(path, sizeof(path), "/dev/video%u", device->id);
	device->accessible = access(path, R_OK|W_OK) >= 0;
	spa_log_debug(this->log, "%s accessible:%u", path, device->accessible);

	return device->accessible;
}

static void process_device(struct impl *this, enum action action, struct device *device)
{
	switch (action) {
	case ACTION_CHANGE:
		check_access(this, device);
		if (device->accessible && !device->emitted) {
			emit_object_info(this, device);
		} else if (!device->accessible && device->emitted) {
			device->emitted = false;
			spa_device_emit_object_info(&this->hooks, device->id, NULL);
		}
		break;
	case ACTION_REMOVE: {
		bool emitted = device->emitted;
		uint32_t id = device->id;

		remove_device(this, device);

		if (emitted)
			spa_device_emit_object_info(&this->hooks, id, NULL);
		break;
	}
	}
}

static void process_udev_device(struct impl *this, enum action action, struct udev_device *udev_device)
{
	struct device *device;
	uint32_t id;

	if ((id = get_device_id(this, udev_device)) == SPA_ID_INVALID)
		return;

	device = find_device(this, id);
	if (action == ACTION_CHANGE && !device)
		device = add_device(this, id, udev_device);

	if (!device)
		return;

	process_device(this, action, device);
}

static int stop_inotify(struct impl *this)
{
	if (this->notify.fd == -1)
		return 0;
	spa_log_info(this->log, "stop inotify");

	for (size_t i = 0; i < this->n_devices; i++)
		stop_watching_device(this, &this->devices[i]);

	spa_loop_remove_source(this->main_loop, &this->notify);
	close(this->notify.fd);
	this->notify.fd = -1;
	return 0;
}

static void impl_on_notify_events(struct spa_source *source)
{
	struct impl *this = source->data;
	union {
		unsigned char name[sizeof(struct inotify_event) + NAME_MAX + 1];
		struct inotify_event e; /* for appropriate alignment */
	} buf;

	while (true) {
		ssize_t len;
		const struct inotify_event *event;
		void *p, *e;

		len = read(source->fd, &buf, sizeof(buf));
		if (len <= 0)
			break;

		e = SPA_PTROFF(&buf, len, void);

		for (p = &buf; p < e;
		    p = SPA_PTROFF(p, sizeof(struct inotify_event) + event->len, void)) {
			event = (const struct inotify_event *) p;
			struct device *device = NULL;

			for (size_t i = 0; i < this->n_devices; i++) {
				if (this->devices[i].inotify_wd == event->wd) {
					device = &this->devices[i];
					break;
				}
			}

			if (!device)
				continue;

			if (event->mask & IN_ATTRIB)
				process_device(this, ACTION_CHANGE, device);

			if (event->mask & IN_IGNORED)
				device->inotify_wd = -1;
		}
	}
}

static int start_inotify(struct impl *this)
{
	int notify_fd;

#ifdef HAVE_SYSTEMD
	/* Do not use inotify when using logind session monitoring */
	if (this->logind_monitor)
		return 0;
#endif

	if (this->notify.fd != -1)
		return 0;

	if ((notify_fd = inotify_init1(IN_CLOEXEC | IN_NONBLOCK)) < 0)
		return -errno;

	spa_log_info(this->log, "start inotify");
	this->notify.func = impl_on_notify_events;
	this->notify.data = this;
	this->notify.fd = notify_fd;
	this->notify.mask = SPA_IO_IN | SPA_IO_ERR;

	spa_loop_add_source(this->main_loop, &this->notify);

	return 0;
}

#ifdef HAVE_SYSTEMD
static void impl_on_logind_events(struct spa_source *source)
{
	struct impl *this = source->data;

	/* Recheck access on all v4l2 devices on logind session changes */
	for (size_t i = 0; i < this->n_devices; i++)
		process_device(this, ACTION_CHANGE, &this->devices[i]);

	sd_login_monitor_flush(this->logind_monitor);
}

static int start_logind(struct impl *this)
{
	int res;

	if (this->logind_monitor)
		return 0;

	/* If we are not actually running logind become a NOP */
	if (access("/run/systemd/seats/", F_OK) < 0)
		return 0;

	res = sd_login_monitor_new("session", &this->logind_monitor);
	if (res < 0)
		return res;

	spa_log_info(this->log, "start logind monitoring");

	this->logind.func = impl_on_logind_events;
	this->logind.data = this;
	this->logind.fd = sd_login_monitor_get_fd(this->logind_monitor);
	this->logind.mask = SPA_IO_IN | SPA_IO_ERR;

	spa_loop_add_source(this->main_loop, &this->logind);

	return 0;
}

static void stop_logind(struct impl *this)
{
	if (this->logind_monitor) {
		spa_loop_remove_source(this->main_loop, &this->logind);
		sd_login_monitor_unref(this->logind_monitor);
		this->logind_monitor = NULL;
	}
}
#else
/* Stubs to avoid more ifdefs below */
static int start_logind(struct impl *this)
{
	return 0;
}

static void stop_logind(struct impl *this)
{
}
#endif

static void impl_on_fd_events(struct spa_source *source)
{
	struct impl *this = source->data;
	struct udev_device *dev;
	const char *action;

	dev = udev_monitor_receive_device(this->umonitor);
	if (dev == NULL)
		return;

	if ((action = udev_device_get_action(dev)) == NULL)
		action = "change";

	spa_log_debug(this->log, "action %s", action);

	if (spa_streq(action, "add") ||
	    spa_streq(action, "change")) {
		process_udev_device(this, ACTION_CHANGE, dev);
	} else if (spa_streq(action, "remove")) {
		process_udev_device(this, ACTION_REMOVE, dev);
	}
	udev_device_unref(dev);
}

static int start_monitor(struct impl *this)
{
	int res;

	if (this->umonitor != NULL)
		return 0;

	this->umonitor = udev_monitor_new_from_netlink(this->udev, "udev");
	if (this->umonitor == NULL)
		return -ENOMEM;

	udev_monitor_filter_add_match_subsystem_devtype(this->umonitor,
							"video4linux", NULL);
	udev_monitor_enable_receiving(this->umonitor);

	this->source.func = impl_on_fd_events;
	this->source.data = this;
	this->source.fd = udev_monitor_get_fd(this->umonitor);
	this->source.mask = SPA_IO_IN | SPA_IO_ERR;

	spa_log_debug(this->log, "monitor %p", this->umonitor);
	spa_loop_add_source(this->main_loop, &this->source);

	if ((res = start_logind(this)) < 0)
		return res;

	if ((res = start_inotify(this)) < 0)
		return res;

	return 0;
}

static int stop_monitor(struct impl *this)
{
	if (this->umonitor == NULL)
		return 0;

	clear_devices (this);

	spa_loop_remove_source(this->main_loop, &this->source);
	udev_monitor_unref(this->umonitor);
	this->umonitor = NULL;

	stop_inotify(this);
	stop_logind(this);

	return 0;
}

static int enum_devices(struct impl *this)
{
	struct udev_enumerate *enumerate;
	struct udev_list_entry *devices;

	enumerate = udev_enumerate_new(this->udev);
	if (enumerate == NULL)
		return -ENOMEM;

	udev_enumerate_add_match_subsystem(enumerate, "video4linux");
	udev_enumerate_scan_devices(enumerate);

	for (devices = udev_enumerate_get_list_entry(enumerate); devices;
			devices = udev_list_entry_get_next(devices)) {
		struct udev_device *dev;

		dev = udev_device_new_from_syspath(this->udev, udev_list_entry_get_name(devices));
		if (dev == NULL)
			continue;

		process_udev_device(this, ACTION_CHANGE, dev);

		udev_device_unref(dev);
	}
	udev_enumerate_unref(enumerate);

	return 0;
}

static const struct spa_dict_item device_info_items[] = {
	{ SPA_KEY_DEVICE_API, "udev" },
	{ SPA_KEY_DEVICE_NICK, "v4l2-udev" },
	{ SPA_KEY_API_UDEV_MATCH, "video4linux" },
};

static void emit_device_info(struct impl *this, bool full)
{
	uint64_t old = full ? this->info.change_mask : 0;
	if (full)
		this->info.change_mask = this->info_all;
	if (this->info.change_mask) {
		this->info.props = &SPA_DICT_INIT_ARRAY(device_info_items);
		spa_device_emit_info(&this->hooks, &this->info);
		this->info.change_mask = old;
	}
}

static void impl_hook_removed(struct spa_hook *hook)
{
	struct impl *this = hook->priv;
	if (spa_hook_list_is_empty(&this->hooks)) {
		stop_monitor(this);
		impl_udev_close(this);
	}
}

static int
impl_device_add_listener(void *object, struct spa_hook *listener,
		const struct spa_device_events *events, void *data)
{
	int res;
	struct impl *this = object;
        struct spa_hook_list save;

	spa_return_val_if_fail(this != NULL, -EINVAL);
	spa_return_val_if_fail(events != NULL, -EINVAL);

	if ((res = impl_udev_open(this)) < 0)
		return res;

        spa_hook_list_isolate(&this->hooks, &save, listener, events, data);

	emit_device_info(this, true);

	if ((res = start_monitor(this)) < 0)
		return res;

	if ((res = enum_devices(this)) < 0)
		return res;

        spa_hook_list_join(&this->hooks, &save);

	listener->removed = impl_hook_removed;
	listener->priv = this;

	return 0;
}

static const struct spa_device_methods impl_device = {
	SPA_VERSION_DEVICE_METHODS,
	.add_listener = impl_device_add_listener,
};

static int impl_get_interface(struct spa_handle *handle, const char *type, void **interface)
{
	struct impl *this;

	spa_return_val_if_fail(handle != NULL, -EINVAL);
	spa_return_val_if_fail(interface != NULL, -EINVAL);

	this = (struct impl *) handle;

	if (spa_streq(type, SPA_TYPE_INTERFACE_Device))
		*interface = &this->device;
	else
		return -ENOENT;

	return 0;
}

static int impl_clear(struct spa_handle *handle)
{
	struct impl *this = (struct impl *) handle;
	stop_monitor(this);
	impl_udev_close(this);
	return 0;
}

static size_t
impl_get_size(const struct spa_handle_factory *factory,
	      const struct spa_dict *params)
{
	return sizeof(struct impl);
}

static int
impl_init(const struct spa_handle_factory *factory,
	  struct spa_handle *handle,
	  const struct spa_dict *info,
	  const struct spa_support *support,
	  uint32_t n_support)
{
	struct impl *this;

	spa_return_val_if_fail(factory != NULL, -EINVAL);
	spa_return_val_if_fail(handle != NULL, -EINVAL);

	handle->get_interface = impl_get_interface;
	handle->clear = impl_clear;

	this = (struct impl *) handle;
	this->notify.fd = -1;
#ifdef HAVE_SYSTEMD
	this->logind_monitor = NULL;
#endif

	this->log = spa_support_find(support, n_support, SPA_TYPE_INTERFACE_Log);
	this->main_loop = spa_support_find(support, n_support, SPA_TYPE_INTERFACE_Loop);

	if (this->main_loop == NULL) {
		spa_log_error(this->log, "a main-loop is needed");
		return -EINVAL;
	}
	spa_hook_list_init(&this->hooks);

	this->device.iface = SPA_INTERFACE_INIT(
			SPA_TYPE_INTERFACE_Device,
			SPA_VERSION_DEVICE,
			&impl_device, this);

	this->info = SPA_DEVICE_INFO_INIT();
	this->info_all = SPA_DEVICE_CHANGE_MASK_FLAGS |
			SPA_DEVICE_CHANGE_MASK_PROPS;
	this->info.flags = 0;

	return 0;
}

static const struct spa_interface_info impl_interfaces[] = {
	{SPA_TYPE_INTERFACE_Device,},
};

static int
impl_enum_interface_info(const struct spa_handle_factory *factory,
			 const struct spa_interface_info **info,
			 uint32_t *index)
{
	spa_return_val_if_fail(factory != NULL, -EINVAL);
	spa_return_val_if_fail(info != NULL, -EINVAL);
	spa_return_val_if_fail(index != NULL, -EINVAL);

	if (*index >= SPA_N_ELEMENTS(impl_interfaces))
		return 0;

	*info = &impl_interfaces[(*index)++];
	return 1;
}

const struct spa_handle_factory spa_v4l2_udev_factory = {
	SPA_VERSION_HANDLE_FACTORY,
	SPA_NAME_API_V4L2_ENUM_UDEV,
	NULL,
	impl_get_size,
	impl_init,
	impl_enum_interface_info,
};