firewire: cdev: add ioctls for manual iso resource management

This adds ioctls for allocation and deallocation of a channel or/and bandwidth without auto-reallocation and without auto-deallocation. The benefit of these ioctls is that libraw1394-style isochronous resource management can be implemented without write access to the IRM's character device file. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

firewire: cdev: add ioctls for manual iso resource management
This adds ioctls for allocation and deallocation of a channel or/and bandwidth without auto-reallocation and without auto-deallocation. The benefit of these ioctls is that libraw1394-style isochronous resource management can be implemented without write access to the IRM's character device file. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Stefan Richter
1 parent b1bda4cdc2
Showing 2 changed files with 86 additions and 23 deletions Side-by-side Diff
drivers/firewire/fw-cdev.c
include/linux/firewire-cdev.h
@@ -121,14 +121,15 @@
 	struct client *client;
 	/* Schedule work and access todo only with client->lock held. */
 	struct delayed_work work;
-	enum {ISO_RES_ALLOC, ISO_RES_REALLOC, ISO_RES_DEALLOC,} todo;
+	enum {ISO_RES_ALLOC, ISO_RES_REALLOC, ISO_RES_DEALLOC,
+	      ISO_RES_ALLOC_ONCE, ISO_RES_DEALLOC_ONCE,} todo;
 	int generation;
 	u64 channels;
 	s32 bandwidth;
 	struct iso_resource_event *e_alloc, *e_dealloc;
 };
  
-static void schedule_iso_resource(struct iso_resource *);
+static int schedule_iso_resource(struct iso_resource *);
 static void release_iso_resource(struct client *, struct client_resource *);
  
 /*
@@ -1033,7 +1034,9 @@
 		skip = todo == ISO_RES_REALLOC &&
 		       r->generation == generation;
 	}
-	free = todo == ISO_RES_DEALLOC;
+	free = todo == ISO_RES_DEALLOC ||
+	       todo == ISO_RES_ALLOC_ONCE ||
+	       todo == ISO_RES_DEALLOC_ONCE;
 	r->generation = generation;
 	spin_unlock_irq(&client->lock);
  
@@ -1044,7 +1047,9 @@
  
 	fw_iso_resource_manage(client->device->card, generation,
 			r->channels, &channel, &bandwidth,
-			todo == ISO_RES_ALLOC || todo == ISO_RES_REALLOC);
+			todo == ISO_RES_ALLOC ||
+			todo == ISO_RES_REALLOC ||
+			todo == ISO_RES_ALLOC_ONCE);
 	/*
 	 * Is this generation outdated already?  As long as this resource sticks
 	 * in the idr, it will be scheduled again for a newer generation or at
@@ -1082,7 +1087,7 @@
 	if (todo == ISO_RES_REALLOC && success)
 		goto out;
  
-	if (todo == ISO_RES_ALLOC) {
+	if (todo == ISO_RES_ALLOC || todo == ISO_RES_ALLOC_ONCE) {
 		e = r->e_alloc;
 		r->e_alloc = NULL;
 	} else {
  
@@ -1106,10 +1111,17 @@
 	client_put(client);
 }
  
-static void schedule_iso_resource(struct iso_resource *r)
+static int schedule_iso_resource(struct iso_resource *r)
 {
-	if (schedule_delayed_work(&r->work, 0))
-		client_get(r->client);
+	int scheduled;
+
+	client_get(r->client);
+
+	scheduled = schedule_delayed_work(&r->work, 0);
+	if (!scheduled)
+		client_put(r->client);
+
+	return scheduled;
 }
  
 static void release_iso_resource(struct client *client,
  
@@ -1124,9 +1136,9 @@
 	spin_unlock_irq(&client->lock);
 }
  
-static int ioctl_allocate_iso_resource(struct client *client, void *buffer)
+static int init_iso_resource(struct client *client,
+		struct fw_cdev_allocate_iso_resource *request, int todo)
 {
-	struct fw_cdev_allocate_iso_resource *request = buffer;
 	struct iso_resource_event *e1, *e2;
 	struct iso_resource *r;
 	int ret;
@@ -1146,7 +1158,7 @@
  
 	INIT_DELAYED_WORK(&r->work, iso_resource_work);
 	r->client	= client;
-	r->todo		= ISO_RES_ALLOC;
+	r->todo		= todo;
 	r->generation	= -1;
 	r->channels	= request->channels;
 	r->bandwidth	= request->bandwidth;
@@ -1158,8 +1170,14 @@
 	e2->resource.closure	= request->closure;
 	e2->resource.type	= FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED;
  
-	r->resource.release = release_iso_resource;
-	ret = add_client_resource(client, &r->resource, GFP_KERNEL);
+	if (todo == ISO_RES_ALLOC) {
+		r->resource.release = release_iso_resource;
+		ret = add_client_resource(client, &r->resource, GFP_KERNEL);
+	} else {
+		r->resource.release = NULL;
+		r->resource.handle = -1;
+		ret = schedule_iso_resource(r) ? 0 : -ENOMEM;
+	}
 	if (ret < 0)
 		goto fail;
 	request->handle = r->resource.handle;
@@ -1173,6 +1191,13 @@
 	return ret;
 }
  
+static int ioctl_allocate_iso_resource(struct client *client, void *buffer)
+{
+	struct fw_cdev_allocate_iso_resource *request = buffer;
+
+	return init_iso_resource(client, request, ISO_RES_ALLOC);
+}
+
 static int ioctl_deallocate_iso_resource(struct client *client, void *buffer)
 {
 	struct fw_cdev_deallocate *request = buffer;
@@ -1181,6 +1206,20 @@
 				       release_iso_resource, NULL);
 }
  
+static int ioctl_allocate_iso_resource_once(struct client *client, void *buffer)
+{
+	struct fw_cdev_allocate_iso_resource *request = buffer;
+
+	return init_iso_resource(client, request, ISO_RES_ALLOC_ONCE);
+}
+
+static int ioctl_deallocate_iso_resource_once(struct client *client, void *buffer)
+{
+	struct fw_cdev_allocate_iso_resource *request = buffer;
+
+	return init_iso_resource(client, request, ISO_RES_DEALLOC_ONCE);
+}
+
 static int (* const ioctl_handlers[])(struct client *client, void *buffer) = {
 	ioctl_get_info,
 	ioctl_send_request,
@@ -1197,6 +1236,8 @@
 	ioctl_get_cycle_timer,
 	ioctl_allocate_iso_resource,
 	ioctl_deallocate_iso_resource,
+	ioctl_allocate_iso_resource_once,
+	ioctl_deallocate_iso_resource_once,
 };
  
 static int dispatch_ioctl(struct client *client,
@@ -151,7 +151,7 @@
 /**
  * struct fw_cdev_event_iso_resource - Iso resources were allocated or freed
  * @closure:	See &fw_cdev_event_common;
- *		set by %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE ioctl
+ *		set by %FW_CDEV_IOC_(DE)ALLOCATE_ISO_RESOURCE(_ONCE) ioctl
  * @type:	%FW_CDEV_EVENT_ISO_RESOURCE_ALLOCATED or
  *		%FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED
  * @handle:	Reference by which an allocated resource can be deallocated
  
@@ -164,12 +164,12 @@
  * resource was allocated at the IRM.  The client has to check @channel and
  * @bandwidth for whether the allocation actually succeeded.
  *
- * @channel is <0 if no channel was allocated.
- * @bandwidth is 0 if no bandwidth was allocated.
- *
  * An %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED event is sent after an isochronous
  * resource was deallocated at the IRM.  It is also sent when automatic
  * reallocation after a bus reset failed.
+ *
+ * @channel is <0 if no channel was (de)allocated or if reallocation failed.
+ * @bandwidth is 0 if no bandwidth was (de)allocated or if reallocation failed.
  */
 struct fw_cdev_event_iso_resource {
 	__u64 closure;
@@ -225,8 +225,10 @@
 #define FW_CDEV_IOC_GET_CYCLE_TIMER	_IOR('#', 0x0c, struct fw_cdev_get_cycle_timer)
  
 /* available since kernel version 2.6.30 */
-#define FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE   _IOWR('#', 0x0d, struct fw_cdev_allocate_iso_resource)
-#define FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE _IOW('#', 0x0e, struct fw_cdev_deallocate)
+#define FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE       _IOWR('#', 0x0d, struct fw_cdev_allocate_iso_resource)
+#define FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE      _IOW('#', 0x0e, struct fw_cdev_deallocate)
+#define FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE_ONCE   _IOW('#', 0x0f, struct fw_cdev_allocate_iso_resource)
+#define FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE_ONCE _IOW('#', 0x10, struct fw_cdev_allocate_iso_resource)
  
 /* FW_CDEV_VERSION History
  *
  
@@ -523,11 +525,12 @@
 };
  
 /**
- * struct fw_cdev_allocate_iso_resource - Allocate a channel or bandwidth
+ * struct fw_cdev_allocate_iso_resource - (De)allocate a channel or bandwidth
  * @closure:	Passed back to userspace in correponding iso resource events
- * @channels:	Isochronous channels of which one is to be allocated
- * @bandwidth:	Isochronous bandwidth units to be allocated
- * @handle:	Handle to the allocation, written by the kernel
+ * @channels:	Isochronous channels of which one is to be (de)allocated
+ * @bandwidth:	Isochronous bandwidth units to be (de)allocated
+ * @handle:	Handle to the allocation, written by the kernel (only valid in
+ *		case of %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE ioctls)
  *
  * The %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE ioctl initiates allocation of an
  * isochronous channel and/or of isochronous bandwidth at the isochronous
@@ -538,6 +541,25 @@
  * Should a reallocation fail, an %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED event
  * will be sent.  The kernel will also automatically deallocate the resources
  * when the file descriptor is closed.
+ *
+ * The %FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE ioctl can be used to initiate
+ * deallocation of resources which were allocated as described above.
+ * An %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED event concludes this operation.
+ *
+ * The %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE_ONCE ioctl is a variant of allocation
+ * without automatic re- or deallocation.
+ * An %FW_CDEV_EVENT_ISO_RESOURCE_ALLOCATED event concludes this operation,
+ * indicating success or failure in its data.
+ *
+ * The %FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE_ONCE ioctl works like
+ * %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE_ONCE except that resources are freed
+ * instead of allocated.  At most one channel may be specified in this ioctl.
+ * An %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED event concludes this operation.
+ *
+ * To summarize, %FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE allocates iso resources
+ * for the lifetime of the fd or handle.
+ * In contrast, %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE_ONCE allocates iso resources
+ * for the duration of a bus generation.
  *
  * @channels is a host-endian bitfield with the most significant bit
  * representing channel 0 and the least significant bit representing channel 63:
...	...	@@ -121,14 +121,15 @@
121	121	struct client *client;
122	122	/* Schedule work and access todo only with client->lock held. */
123	123	struct delayed_work work;
124		- enum {ISO_RES_ALLOC, ISO_RES_REALLOC, ISO_RES_DEALLOC,} todo;
	124	+ enum {ISO_RES_ALLOC, ISO_RES_REALLOC, ISO_RES_DEALLOC,
	125	+ ISO_RES_ALLOC_ONCE, ISO_RES_DEALLOC_ONCE,} todo;
125	126	int generation;
126	127	u64 channels;
127	128	s32 bandwidth;
128	129	struct iso_resource_event e_alloc, e_dealloc;
129	130	};
130	131
131		-static void schedule_iso_resource(struct iso_resource *);
	132	+static int schedule_iso_resource(struct iso_resource *);
132	133	static void release_iso_resource(struct client , struct client_resource );
133	134
134	135	/*
...	...	@@ -1033,7 +1034,9 @@
1033	1034	skip = todo == ISO_RES_REALLOC &&
1034	1035	r->generation == generation;
1035	1036	}
1036		- free = todo == ISO_RES_DEALLOC;
	1037	+ free = todo == ISO_RES_DEALLOC \|\|
	1038	+ todo == ISO_RES_ALLOC_ONCE \|\|
	1039	+ todo == ISO_RES_DEALLOC_ONCE;
1037	1040	r->generation = generation;
1038	1041	spin_unlock_irq(&client->lock);
1039	1042
...	...	@@ -1044,7 +1047,9 @@
1044	1047
1045	1048	fw_iso_resource_manage(client->device->card, generation,
1046	1049	r->channels, &channel, &bandwidth,
1047		- todo == ISO_RES_ALLOC \|\| todo == ISO_RES_REALLOC);
	1050	+ todo == ISO_RES_ALLOC \|\|
	1051	+ todo == ISO_RES_REALLOC \|\|
	1052	+ todo == ISO_RES_ALLOC_ONCE);
1048	1053	/*
1049	1054	* Is this generation outdated already? As long as this resource sticks
1050	1055	* in the idr, it will be scheduled again for a newer generation or at
...	...	@@ -1082,7 +1087,7 @@
1082	1087	if (todo == ISO_RES_REALLOC && success)
1083	1088	goto out;
1084	1089
1085		- if (todo == ISO_RES_ALLOC) {
	1090	+ if (todo == ISO_RES_ALLOC \|\| todo == ISO_RES_ALLOC_ONCE) {
1086	1091	e = r->e_alloc;
1087	1092	r->e_alloc = NULL;
1088	1093	} else {
1089	1094
...	...	@@ -1106,10 +1111,17 @@
1106	1111	client_put(client);
1107	1112	}
1108	1113
1109		-static void schedule_iso_resource(struct iso_resource *r)
	1114	+static int schedule_iso_resource(struct iso_resource *r)
1110	1115	{
1111		- if (schedule_delayed_work(&r->work, 0))
1112		- client_get(r->client);
	1116	+ int scheduled;
	1117	+
	1118	+ client_get(r->client);
	1119	+
	1120	+ scheduled = schedule_delayed_work(&r->work, 0);
	1121	+ if (!scheduled)
	1122	+ client_put(r->client);
	1123	+
	1124	+ return scheduled;
1113	1125	}
1114	1126
1115	1127	static void release_iso_resource(struct client *client,
1116	1128
...	...	@@ -1124,9 +1136,9 @@
1124	1136	spin_unlock_irq(&client->lock);
1125	1137	}
1126	1138
1127		-static int ioctl_allocate_iso_resource(struct client client, void buffer)
	1139	+static int init_iso_resource(struct client *client,
	1140	+ struct fw_cdev_allocate_iso_resource *request, int todo)
1128	1141	{
1129		- struct fw_cdev_allocate_iso_resource *request = buffer;
1130	1142	struct iso_resource_event e1, e2;
1131	1143	struct iso_resource *r;
1132	1144	int ret;
...	...	@@ -1146,7 +1158,7 @@
1146	1158
1147	1159	INIT_DELAYED_WORK(&r->work, iso_resource_work);
1148	1160	r->client = client;
1149		- r->todo = ISO_RES_ALLOC;
	1161	+ r->todo = todo;
1150	1162	r->generation = -1;
1151	1163	r->channels = request->channels;
1152	1164	r->bandwidth = request->bandwidth;
...	...	@@ -1158,8 +1170,14 @@
1158	1170	e2->resource.closure = request->closure;
1159	1171	e2->resource.type = FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED;
1160	1172
1161		- r->resource.release = release_iso_resource;
1162		- ret = add_client_resource(client, &r->resource, GFP_KERNEL);
	1173	+ if (todo == ISO_RES_ALLOC) {
	1174	+ r->resource.release = release_iso_resource;
	1175	+ ret = add_client_resource(client, &r->resource, GFP_KERNEL);
	1176	+ } else {
	1177	+ r->resource.release = NULL;
	1178	+ r->resource.handle = -1;
	1179	+ ret = schedule_iso_resource(r) ? 0 : -ENOMEM;
	1180	+ }
1163	1181	if (ret < 0)
1164	1182	goto fail;
1165	1183	request->handle = r->resource.handle;
...	...	@@ -1173,6 +1191,13 @@
1173	1191	return ret;
1174	1192	}
1175	1193
	1194	+static int ioctl_allocate_iso_resource(struct client client, void buffer)
	1195	+{
	1196	+ struct fw_cdev_allocate_iso_resource *request = buffer;
	1197	+
	1198	+ return init_iso_resource(client, request, ISO_RES_ALLOC);
	1199	+}
	1200	+
1176	1201	static int ioctl_deallocate_iso_resource(struct client client, void buffer)
1177	1202	{
1178	1203	struct fw_cdev_deallocate *request = buffer;
...	...	@@ -1181,6 +1206,20 @@
1181	1206	release_iso_resource, NULL);
1182	1207	}
1183	1208
	1209	+static int ioctl_allocate_iso_resource_once(struct client client, void buffer)
	1210	+{
	1211	+ struct fw_cdev_allocate_iso_resource *request = buffer;
	1212	+
	1213	+ return init_iso_resource(client, request, ISO_RES_ALLOC_ONCE);
	1214	+}
	1215	+
	1216	+static int ioctl_deallocate_iso_resource_once(struct client client, void buffer)
	1217	+{
	1218	+ struct fw_cdev_allocate_iso_resource *request = buffer;
	1219	+
	1220	+ return init_iso_resource(client, request, ISO_RES_DEALLOC_ONCE);
	1221	+}
	1222	+
1184	1223	static int (* const ioctl_handlers[])(struct client client, void buffer) = {
1185	1224	ioctl_get_info,
1186	1225	ioctl_send_request,
...	...	@@ -1197,6 +1236,8 @@
1197	1236	ioctl_get_cycle_timer,
1198	1237	ioctl_allocate_iso_resource,
1199	1238	ioctl_deallocate_iso_resource,
	1239	+ ioctl_allocate_iso_resource_once,
	1240	+ ioctl_deallocate_iso_resource_once,
1200	1241	};
1201	1242
1202	1243	static int dispatch_ioctl(struct client *client,
...	...	@@ -151,7 +151,7 @@
151	151	/**
152	152	* struct fw_cdev_event_iso_resource - Iso resources were allocated or freed
153	153	* @closure: See &fw_cdev_event_common;
154		- * set by %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE ioctl
	154	+ * set by %FW_CDEV_IOC_(DE)ALLOCATE_ISO_RESOURCE(_ONCE) ioctl
155	155	* @type: %FW_CDEV_EVENT_ISO_RESOURCE_ALLOCATED or
156	156	* %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED
157	157	* @handle: Reference by which an allocated resource can be deallocated
158	158
...	...	@@ -164,12 +164,12 @@
164	164	* resource was allocated at the IRM. The client has to check @channel and
165	165	* @bandwidth for whether the allocation actually succeeded.
166	166	*
167		- * @channel is <0 if no channel was allocated.
168		- * @bandwidth is 0 if no bandwidth was allocated.
169		- *
170	167	* An %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED event is sent after an isochronous
171	168	* resource was deallocated at the IRM. It is also sent when automatic
172	169	* reallocation after a bus reset failed.
	170	+ *
	171	+ * @channel is <0 if no channel was (de)allocated or if reallocation failed.
	172	+ * @bandwidth is 0 if no bandwidth was (de)allocated or if reallocation failed.
173	173	*/
174	174	struct fw_cdev_event_iso_resource {
175	175	__u64 closure;
...	...	@@ -225,8 +225,10 @@
225	225	#define FW_CDEV_IOC_GET_CYCLE_TIMER _IOR('#', 0x0c, struct fw_cdev_get_cycle_timer)
226	226
227	227	/* available since kernel version 2.6.30 */
228		-#define FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE _IOWR('#', 0x0d, struct fw_cdev_allocate_iso_resource)
229		-#define FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE _IOW('#', 0x0e, struct fw_cdev_deallocate)
	228	+#define FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE _IOWR('#', 0x0d, struct fw_cdev_allocate_iso_resource)
	229	+#define FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE _IOW('#', 0x0e, struct fw_cdev_deallocate)
	230	+#define FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE_ONCE _IOW('#', 0x0f, struct fw_cdev_allocate_iso_resource)
	231	+#define FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE_ONCE _IOW('#', 0x10, struct fw_cdev_allocate_iso_resource)
230	232
231	233	/* FW_CDEV_VERSION History
232	234	*
233	235
...	...	@@ -523,11 +525,12 @@
523	525	};
524	526
525	527	/**
526		- * struct fw_cdev_allocate_iso_resource - Allocate a channel or bandwidth
	528	+ * struct fw_cdev_allocate_iso_resource - (De)allocate a channel or bandwidth
527	529	* @closure: Passed back to userspace in correponding iso resource events
528		- * @channels: Isochronous channels of which one is to be allocated
529		- * @bandwidth: Isochronous bandwidth units to be allocated
530		- * @handle: Handle to the allocation, written by the kernel
	530	+ * @channels: Isochronous channels of which one is to be (de)allocated
	531	+ * @bandwidth: Isochronous bandwidth units to be (de)allocated
	532	+ * @handle: Handle to the allocation, written by the kernel (only valid in
	533	+ * case of %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE ioctls)
531	534	*
532	535	* The %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE ioctl initiates allocation of an
533	536	* isochronous channel and/or of isochronous bandwidth at the isochronous
...	...	@@ -538,6 +541,25 @@
538	541	* Should a reallocation fail, an %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED event
539	542	* will be sent. The kernel will also automatically deallocate the resources
540	543	* when the file descriptor is closed.
	544	+ *
	545	+ * The %FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE ioctl can be used to initiate
	546	+ * deallocation of resources which were allocated as described above.
	547	+ * An %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED event concludes this operation.
	548	+ *
	549	+ * The %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE_ONCE ioctl is a variant of allocation
	550	+ * without automatic re- or deallocation.
	551	+ * An %FW_CDEV_EVENT_ISO_RESOURCE_ALLOCATED event concludes this operation,
	552	+ * indicating success or failure in its data.
	553	+ *
	554	+ * The %FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE_ONCE ioctl works like
	555	+ * %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE_ONCE except that resources are freed
	556	+ * instead of allocated. At most one channel may be specified in this ioctl.
	557	+ * An %FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED event concludes this operation.
	558	+ *
	559	+ * To summarize, %FW_CDEV_IOC_DEALLOCATE_ISO_RESOURCE allocates iso resources
	560	+ * for the lifetime of the fd or handle.
	561	+ * In contrast, %FW_CDEV_IOC_ALLOCATE_ISO_RESOURCE_ONCE allocates iso resources
	562	+ * for the duration of a bus generation.
541	563	*
542	564	* @channels is a host-endian bitfield with the most significant bit
543	565	* representing channel 0 and the least significant bit representing channel 63: