firewire: Document userspace ioctl interface.

The isochronous packet format is still not documented, but this
is a good first step.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (format, wording)

include/linux/firewire-cdev.h

@@ -30,16 +30,38 @@
 #define FW_CDEV_EVENT_REQUEST		0x02
 #define FW_CDEV_EVENT_ISO_INTERRUPT	0x03
 
-/* The 'closure' fields are for user space to use.  Data passed in the
- * 'closure' field for a request will be returned in the corresponding
- * event.  It's a 64-bit type so that it's a fixed size type big
- * enough to hold a pointer on all platforms. */
-
+/**
+ * struct fw_cdev_event_common - Common part of all fw_cdev_event_ types
+ * @closure:	For arbitrary use by userspace
+ * @type:	Discriminates the fw_cdev_event_ types
+ *
+ * This struct may be used to access generic members of all fw_cdev_event_
+ * types regardless of the specific type.
+ *
+ * Data passed in the @closure field for a request will be returned in the
+ * corresponding event.  It is big enough to hold a pointer on all platforms.
+ * The ioctl used to set @closure depends on the @type of event.
+ */
 struct fw_cdev_event_common {
 	__u64 closure;
 	__u32 type;
 };
 
+/**
+ * struct fw_cdev_event_bus_reset - Sent when a bus reset occurred
+ * @closure:	See &fw_cdev_event_common; set by %FW_CDEV_IOC_GET_INFO ioctl
+ * @type:	See &fw_cdev_event_common; always %FW_CDEV_EVENT_BUS_RESET
+ * @node_id:       New node ID of this node
+ * @local_node_id: Node ID of the local node, i.e. of the controller
+ * @bm_node_id:    Node ID of the bus manager
+ * @irm_node_id:   Node ID of the iso resource manager
+ * @root_node_id:  Node ID of the root node
+ * @generation:    New bus generation
+ *
+ * This event is sent when the bus the device belongs to goes through a bus
+ * reset.  It provides information about the new bus configuration, such as
+ * new node ID for this device, new root ID, and others.
+ */
 struct fw_cdev_event_bus_reset {
 	__u64 closure;
 	__u32 type;
@@ -51,6 +73,20 @@ struct fw_cdev_event_bus_reset {
 	__u32 generation;
 };
 
+/**
+ * struct fw_cdev_event_response - Sent when a response packet was received
+ * @closure:	See &fw_cdev_event_common;
+ *		set by %FW_CDEV_IOC_SEND_REQUEST ioctl
+ * @type:	See &fw_cdev_event_common; always %FW_CDEV_EVENT_RESPONSE
+ * @rcode:	Response code returned by the remote node
+ * @length:	Data length, i.e. the response's payload size in bytes
+ * @data:	Payload data, if any
+ *
+ * This event is sent when the stack receives a response to an outgoing request
+ * sent by %FW_CDEV_IOC_SEND_REQUEST ioctl.  The payload data for responses
+ * carrying data (read and lock responses) follows immediately and can be
+ * accessed through the @data field.
+ */
 struct fw_cdev_event_response {
 	__u64 closure;
 	__u32 type;
@@ -59,6 +95,25 @@ struct fw_cdev_event_response {
 	__u32 data[0];
 };
 
+/**
+ * struct fw_cdev_event_request - Sent on incoming request to an address region
+ * @closure:	See &fw_cdev_event_common; set by %FW_CDEV_IOC_ALLOCATE ioctl
+ * @type:	See &fw_cdev_event_common; always %FW_CDEV_EVENT_REQUEST
+ * @tcode:	Transaction code of the incoming request
+ * @offset:	The offset into the 48-bit per-node address space
+ * @handle:	Reference to the kernel-side pending request
+ * @length:	Data length, i.e. the request's payload size in bytes
+ * @data:	Incoming data, if any
+ *
+ * This event is sent when the stack receives an incoming request to an address
+ * region registered using the %FW_CDEV_IOC_ALLOCATE ioctl.  The request is
+ * guaranteed to be completely contained in the specified region.  Userspace is
+ * responsible for sending the response by %FW_CDEV_IOC_SEND_RESPONSE ioctl,
+ * using the same @handle.
+ *
+ * The payload data for requests carrying data (write and lock requests)
+ * follows immediately and can be accessed through the @data field.
+ */
 struct fw_cdev_event_request {
 	__u64 closure;
 	__u32 type;
@@ -69,14 +124,39 @@ struct fw_cdev_event_request {
 	__u32 data[0];
 };
 
+/**
+ * struct fw_cdev_event_iso_interrupt - Sent when an iso packet was completed
+ * @closure:	See &fw_cdev_event_common;
+ *		set by %FW_CDEV_CREATE_ISO_CONTEXT ioctl
+ * @type:	See &fw_cdev_event_common; always %FW_CDEV_EVENT_ISO_INTERRUPT
+ * @cycle:	Cycle counter of the interrupt packet
+ * @header_length: Total length of following headers, in bytes
+ * @header:	Stripped headers, if any
+ *
+ * This event is sent when the controller has completed an &fw_cdev_iso_packet
+ * with the %FW_CDEV_ISO_INTERRUPT bit set.  In the receive case, the headers
+ * stripped of all packets up until and including the interrupt packet are
+ * returned in the @header field.
+ */
 struct fw_cdev_event_iso_interrupt {
 	__u64 closure;
 	__u32 type;
 	__u32 cycle;
-	__u32 header_length;	/* Length in bytes of following headers. */
+	__u32 header_length;
 	__u32 header[0];
 };
 
+/**
+ * union fw_cdev_event - Convenience union of fw_cdev_event_ types
+ * @common:        Valid for all types
+ * @bus_reset:     Valid if @common.type == %FW_CDEV_EVENT_BUS_RESET
+ * @response:      Valid if @common.type == %FW_CDEV_EVENT_RESPONSE
+ * @request:       Valid if @common.type == %FW_CDEV_EVENT_REQUEST
+ * @iso_interrupt: Valid if @common.type == %FW_CDEV_EVENT_ISO_INTERRUPT
+ *
+ * Convenience union for userspace use.  Events could be read(2) into a char
+ * buffer and then cast to this union for further processing.
+ */
 union fw_cdev_event {
 	struct fw_cdev_event_common common;
 	struct fw_cdev_event_bus_reset bus_reset;
@@ -105,35 +185,47 @@ union fw_cdev_event {
  */
 #define FW_CDEV_VERSION		1
 
+/**
+ * struct fw_cdev_get_info - General purpose information ioctl
+ * @version:	The version field is just a running serial number.
+ *		We never break backwards compatibility, but may add more
+ *		structs and ioctls in later revisions.
+ * @rom_length:	If @rom is non-zero, at most rom_length bytes of configuration
+ *		ROM will be copied into that user space address.  In either
+ *		case, @rom_length is updated with the actual length of the
+ *		configuration ROM.
+ * @rom:	If non-zero, address of a buffer to be filled by a copy of the
+ *		local node's configuration ROM
+ * @bus_reset:	If non-zero, address of a buffer to be filled by a
+ *		&struct fw_cdev_event_bus_reset with the current state
+ *		of the bus.  This does not cause a bus reset to happen.
+ * @bus_reset_closure: Value of &closure in this and subsequent bus reset events
+ * @card:	The index of the card this device belongs to
+ */
 struct fw_cdev_get_info {
-	/* The version field is just a running serial number.  We
-	 * never break backwards compatibility.  Userspace passes in
-	 * the version it expects and the kernel passes back the
-	 * highest version it can provide.  Even if the structs in
-	 * this interface are extended in a later version, the kernel
-	 * will not copy back more data than what was present in the
-	 * interface version userspace expects. */
 	__u32 version;
-
-	/* If non-zero, at most rom_length bytes of config rom will be
-	 * copied into that user space address.  In either case,
-	 * rom_length is updated with the actual length of the config
-	 * rom. */
 	__u32 rom_length;
 	__u64 rom;
-
-	/* If non-zero, a fw_cdev_event_bus_reset struct will be
-	 * copied here with the current state of the bus.  This does
-	 * not cause a bus reset to happen.  The value of closure in
-	 * this and sub-sequent bus reset events is set to
-	 * bus_reset_closure. */
 	__u64 bus_reset;
 	__u64 bus_reset_closure;
-
-	/* The index of the card this devices belongs to. */
 	__u32 card;
 };
 
+/**
+ * struct fw_cdev_send_request - Send an asynchronous request packet
+ * @tcode:	Transaction code of the request
+ * @length:	Length of outgoing payload, in bytes
+ * @offset:	48-bit offset at destination node
+ * @closure:	Passed back to userspace in the response event
+ * @data:	Userspace pointer to payload
+ * @generation:	The bus generation where packet is valid
+ *
+ * Send a request to the device.  This ioctl implements all outgoing requests.
+ * Both quadlet and block request specify the payload as a pointer to the data
+ * in the @data field.  Once the transaction completes, the kernel writes an
+ * &fw_cdev_event_request event back.  The @closure field is passed back to
+ * user space in the response event.
+ */
 struct fw_cdev_send_request {
 	__u32 tcode;
 	__u32 length;
@@ -143,6 +235,19 @@ struct fw_cdev_send_request {
 	__u32 generation;
 };
 
+/**
+ * struct fw_cdev_send_response - Send an asynchronous response packet
+ * @rcode:	Response code as determined by the userspace handler
+ * @length:	Length of outgoing payload, in bytes
+ * @data:	Userspace pointer to payload
+ * @handle:	The handle from the &fw_cdev_event_request
+ *
+ * Send a response to an incoming request.  By setting up an address range using
+ * the %FW_CDEV_IOC_ALLOCATE ioctl, userspace can listen for incoming requests.  An
+ * incoming request will generate an %FW_CDEV_EVENT_REQUEST, and userspace must
+ * send a reply using this ioctl.  The event has a handle to the kernel-side
+ * pending transaction, which should be used with this ioctl.
+ */
 struct fw_cdev_send_response {
 	__u32 rcode;
 	__u32 length;
@@ -150,6 +255,21 @@ struct fw_cdev_send_response {
 	__u32 handle;
 };
 
+/**
+ * struct fw_cdev_allocate - Allocate a CSR address range
+ * @offset:	Start offset of the address range
+ * @closure:	To be passed back to userspace in request events
+ * @length:	Length of the address range, in bytes
+ * @handle:	Handle to the allocation, written by the kernel
+ *
+ * Allocate an address range in the 48-bit address space on the local node
+ * (the controller).  This allows userspace to listen for requests with an
+ * offset within that address range.  When the kernel receives a request
+ * within the range, an &fw_cdev_event_request event will be written back.
+ * The @closure field is passed back to userspace in the response event.
+ * The @handle field is an out parameter, returning a handle to the allocated
+ * range to be used for later deallocation of the range.
+ */
 struct fw_cdev_allocate {
 	__u64 offset;
 	__u64 closure;
@@ -157,6 +277,11 @@ struct fw_cdev_allocate {
 	__u32 handle;
 };
 
+/**
+ * struct fw_cdev_deallocate - Free an address range allocation
+ * @handle:	Handle to the address range, as returned by the kernel when the
+ *		range was allocated
+ */
 struct fw_cdev_deallocate {
 	__u32 handle;
 };
@@ -164,10 +289,41 @@ struct fw_cdev_deallocate {
 #define FW_CDEV_LONG_RESET	0
 #define FW_CDEV_SHORT_RESET	1
 
+/**
+ * struct fw_cdev_initiate_bus_reset - Initiate a bus reset
+ * @type:	%FW_CDEV_SHORT_RESET or %FW_CDEV_LONG_RESET
+ *
+ * Initiate a bus reset for the bus this device is on.  The bus reset can be
+ * either the original (long) bus reset or the arbitrated (short) bus reset
+ * introduced in 1394a-2000.
+ */
 struct fw_cdev_initiate_bus_reset {
-	__u32 type;
+	__u32 type;	/* FW_CDEV_SHORT_RESET or FW_CDEV_LONG_RESET */
 };
 
+/**
+ * struct fw_cdev_add_descriptor - Add contents to the local node's config ROM
+ * @immediate:	If non-zero, immediate key to insert before pointer
+ * @key:	Upper 8 bits of root directory pointer
+ * @data:	Userspace pointer to contents of descriptor block
+ * @length:	Length of descriptor block data, in bytes
+ * @handle:	Handle to the descriptor, written by the kernel
+ *
+ * Add a descriptor block and optionally a preceding immediate key to the local
+ * node's configuration ROM.
+ *
+ * The @key field specifies the upper 8 bits of the descriptor root directory
+ * pointer and the @data and @length fields specify the contents. The @key
+ * should be of the form 0xXX000000. The offset part of the root directory entry
+ * will be filled in by the kernel.
+ *
+ * If not 0, the @immediate field specifies an immediate key which will be
+ * inserted before the root directory pointer.
+ *
+ * If successful, the kernel adds the descriptor and writes back a handle to the
+ * kernel-side object to be used for later removal of the descriptor block and
+ * immediate key.
+ */
 struct fw_cdev_add_descriptor {
 	__u32 immediate;
 	__u32 key;
@@ -176,6 +332,14 @@ struct fw_cdev_add_descriptor {
 	__u32 handle;
 };
 
+/**
+ * struct fw_cdev_remove_descriptor - Remove contents from the configuration ROM
+ * @handle:	Handle to the descriptor, as returned by the kernel when the
+ *		descriptor was added
+ *
+ * Remove a descriptor block and accompanying immediate key from the local
+ * node's configuration ROM.
+ */
 struct fw_cdev_remove_descriptor {
 	__u32 handle;
 };
@@ -183,12 +347,24 @@ struct fw_cdev_remove_descriptor {
 #define FW_CDEV_ISO_CONTEXT_TRANSMIT	0
 #define FW_CDEV_ISO_CONTEXT_RECEIVE	1
 
-#define FW_CDEV_ISO_CONTEXT_MATCH_TAG0		 1
-#define FW_CDEV_ISO_CONTEXT_MATCH_TAG1		 2
-#define FW_CDEV_ISO_CONTEXT_MATCH_TAG2		 4
-#define FW_CDEV_ISO_CONTEXT_MATCH_TAG3		 8
-#define FW_CDEV_ISO_CONTEXT_MATCH_ALL_TAGS	15
-
+/**
+ * struct fw_cdev_create_iso_context - Create a context for isochronous IO
+ * @type:	%FW_CDEV_ISO_CONTEXT_TRANSMIT or %FW_CDEV_ISO_CONTEXT_RECEIVE
+ * @header_size: Header size to strip for receive contexts
+ * @channel:	Channel to bind to
+ * @speed:	Speed to transmit at
+ * @closure:	To be returned in &fw_cdev_event_iso_interrupt
+ * @handle:	Handle to context, written back by kernel
+ *
+ * Prior to sending or receiving isochronous I/O, a context must be created.
+ * The context records information about the transmit or receive configuration
+ * and typically maps to an underlying hardware resource.  A context is set up
+ * for either sending or receiving.  It is bound to a specific isochronous
+ * channel.
+ *
+ * If a context was successfully created, the kernel writes back a handle to the
+ * context, which must be passed in for subsequent operations on that context.
+ */
 struct fw_cdev_create_iso_context {
 	__u32 type;
 	__u32 header_size;
@@ -201,15 +377,49 @@ struct fw_cdev_create_iso_context {
 #define FW_CDEV_ISO_PAYLOAD_LENGTH(v)	(v)
 #define FW_CDEV_ISO_INTERRUPT		(1 << 16)
 #define FW_CDEV_ISO_SKIP		(1 << 17)
+#define FW_CDEV_ISO_SYNC		(1 << 17)
 #define FW_CDEV_ISO_TAG(v)		((v) << 18)
 #define FW_CDEV_ISO_SY(v)		((v) << 20)
 #define FW_CDEV_ISO_HEADER_LENGTH(v)	((v) << 24)
 
+/**
+ * struct fw_cdev_iso_packet - Isochronous packet
+ * @control:	Contains the header length (8 uppermost bits), the sy field
+ *		(4 bits), the tag field (2 bits), a sync flag (1 bit),
+ *		a skip flag (1 bit), an interrupt flag (1 bit), and the
+ *		payload length (16 lowermost bits)
+ * @header:	Header and payload
+ *
+ * &struct fw_cdev_iso_packet is used to describe isochronous packet queues.
+ *
+ * Use the FW_CDEV_ISO_ macros to fill in @control.  The sy and tag fields are
+ * specified by IEEE 1394a and IEC 61883.
+ *
+ * FIXME - finish this documentation
+ */
 struct fw_cdev_iso_packet {
 	__u32 control;
 	__u32 header[0];
 };
 
+/**
+ * struct fw_cdev_queue_iso - Queue isochronous packets for I/O
+ * @packets:	Userspace pointer to packet data
+ * @data:	Pointer into mmap()'ed payload buffer
+ * @size:	Size of packet data in bytes
+ * @handle:	Isochronous context handle
+ *
+ * Queue a number of isochronous packets for reception or transmission.
+ * This ioctl takes a pointer to an array of &fw_cdev_iso_packet structs,
+ * which describe how to transmit from or receive into a contiguous region
+ * of a mmap()'ed payload buffer.  As part of the packet descriptors,
+ * a series of headers can be supplied, which will be prepended to the
+ * payload during DMA.
+ *
+ * The kernel may or may not queue all packets, but will write back updated
+ * values of the @packets, @data and @size fields, so the ioctl can be
+ * resubmitted easily.
+ */
 struct fw_cdev_queue_iso {
 	__u64 packets;
 	__u64 data;
@@ -217,6 +427,23 @@ struct fw_cdev_queue_iso {
 	__u32 handle;
 };
 
+#define FW_CDEV_ISO_CONTEXT_MATCH_TAG0		 1
+#define FW_CDEV_ISO_CONTEXT_MATCH_TAG1		 2
+#define FW_CDEV_ISO_CONTEXT_MATCH_TAG2		 4
+#define FW_CDEV_ISO_CONTEXT_MATCH_TAG3		 8
+#define FW_CDEV_ISO_CONTEXT_MATCH_ALL_TAGS	15
+
+/**
+ * struct fw_cdev_start_iso - Start an isochronous transmission or reception
+ * @cycle:	Cycle in which to start I/O.  If @cycle is greater than or
+ *		equal to 0, the I/O will start on that cycle.
+ * @sync:	Determines the value to wait for for receive packets that have
+ *		the %FW_CDEV_ISO_SYNC bit set
+ * @tags:	Tag filter bit mask.  Only valid for isochronous reception.
+ *		Determines the tag values for which packets will be accepted.
+ *		Use FW_CDEV_ISO_CONTEXT_MATCH_ macros to set @tags.
+ * @handle:	Isochronous context handle within which to transmit or receive
+ */
 struct fw_cdev_start_iso {
 	__s32 cycle;
 	__u32 sync;
@@ -224,6 +451,10 @@ struct fw_cdev_start_iso {
 	__u32 handle;
 };
 
+/**
+ * struct fw_cdev_stop_iso - Stop an isochronous transmission or reception
+ * @handle:	Handle of isochronous context to stop
+ */
 struct fw_cdev_stop_iso {
 	__u32 handle;
 };