firewire: cdev: add PHY packet transmission

Add an FW_CDEV_IOC_SEND_PHY_PACKET ioctl() for /dev/fw* which can be
used to implement bus management related functionality in userspace.

This is also half of the functionality (the transmit part) that is
needed to support a userspace implementation of a VersaPHY transaction
layer.

Safety considerations:

  - PHY packets are generally broadcasts and may have interesting
    effects on PHYs and the bus, e.g. make asynchronous arbitration
    impossible due to too low gap count.  Hence some kind of elevated
    privileges should be required of a process to be able to send
    PHY packets.  This implementation assumes that a process that is
    allowed to open the /dev/fw* of a local node does have this
    privilege.

    There was an inconclusive discussion about introducing POSIX
    capabilities as a means to check for user privileges for these
    kinds of operations.

  - The kernel does not check integrity of the supplied packet data.
    That would be far too much code, considering the many kinds of
    PHY packets.  A process which got the privilege to send these
    packets is trusted to do it correctly.

Just like with the other "send packet" ioctls, a non-blocking API is
chosen; i.e. the ioctl may return even before AT DMA started.  After
transmission, an event for poll()/read() is enqueued.  Most users are
going to need a blocking API, but a blocking userspace wrapper is easy
to implement, and the second of the two existing libraw1394 calls
raw1394_phy_packet_write() and raw1394_start_phy_packet_write() can be
better supported that way.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 64 insertions, 0 deletions

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index acf4fa1..f957199 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -194,6 +194,13 @@ struct iso_resource_event {
 	struct fw_cdev_event_iso_resource iso_resource;
 };
 
+struct outbound_phy_packet_event {
+	struct event event;
+	struct client *client;
+	struct fw_packet p;
+	struct fw_cdev_event_phy_packet phy_packet;
+};
+
 static inline void __user *u64_to_uptr(__u64 value)
 {
 	return (void __user *)(unsigned long)value;
@@ -396,6 +403,7 @@ union ioctl_arg {
 	struct fw_cdev_allocate_iso_resource	allocate_iso_resource;
 	struct fw_cdev_send_stream_packet	send_stream_packet;
 	struct fw_cdev_get_cycle_timer2		get_cycle_timer2;
+	struct fw_cdev_send_phy_packet		send_phy_packet;
 };
 
 static int ioctl_get_info(struct client *client, union ioctl_arg *arg)
@@ -1384,6 +1392,61 @@ static int ioctl_send_stream_packet(struct client *client, union ioctl_arg *arg)
 	return init_request(client, &request, dest, a->speed);
 }
 
+static void outbound_phy_packet_callback(struct fw_packet *packet,
+					 struct fw_card *card, int status)
+{
+	struct outbound_phy_packet_event *e =
+		container_of(packet, struct outbound_phy_packet_event, p);
+
+	switch (status) {
+	/* expected: */
+	case ACK_COMPLETE:	e->phy_packet.rcode = RCODE_COMPLETE;	break;
+	/* should never happen with PHY packets: */
+	case ACK_PENDING:	e->phy_packet.rcode = RCODE_COMPLETE;	break;
+	case ACK_BUSY_X:
+	case ACK_BUSY_A:
+	case ACK_BUSY_B:	e->phy_packet.rcode = RCODE_BUSY;	break;
+	case ACK_DATA_ERROR:	e->phy_packet.rcode = RCODE_DATA_ERROR;	break;
+	case ACK_TYPE_ERROR:	e->phy_packet.rcode = RCODE_TYPE_ERROR;	break;
+	/* stale generation; cancelled; on certain controllers: no ack */
+	default:		e->phy_packet.rcode = status;		break;
+	}
+
+	queue_event(e->client, &e->event,
+		    &e->phy_packet, sizeof(e->phy_packet), NULL, 0);
+	client_put(e->client);
+}
+
+static int ioctl_send_phy_packet(struct client *client, union ioctl_arg *arg)
+{
+	struct fw_cdev_send_phy_packet *a = &arg->send_phy_packet;
+	struct fw_card *card = client->device->card;
+	struct outbound_phy_packet_event *e;
+
+	/* Access policy: Allow this ioctl only on local nodes' device files. */
+	if (!client->device->is_local)
+		return -ENOSYS;
+
+	e = kzalloc(sizeof(*e), GFP_KERNEL);
+	if (e == NULL)
+		return -ENOMEM;
+
+	client_get(client);
+	e->client		= client;
+	e->p.speed		= SCODE_100;
+	e->p.generation		= a->generation;
+	e->p.header[0]		= a->data[0];
+	e->p.header[1]		= a->data[1];
+	e->p.header_length	= 8;
+	e->p.callback		= outbound_phy_packet_callback;
+	e->phy_packet.closure	= a->closure;
+	e->phy_packet.type	= FW_CDEV_EVENT_PHY_PACKET_SENT;
+
+	card->driver->send_request(card, &e->p);
+
+	return 0;
+}
+
 static int (* const ioctl_handlers[])(struct client *, union ioctl_arg *) = {
 	[0x00] = ioctl_get_info,
 	[0x01] = ioctl_send_request,
@@ -1406,6 +1469,7 @@ static int (* const ioctl_handlers[])(struct client *, union ioctl_arg *) = {
 	[0x12] = ioctl_send_broadcast_request,
 	[0x13] = ioctl_send_stream_packet,
 	[0x14] = ioctl_get_cycle_timer2,
+	[0x15] = ioctl_send_phy_packet,
 };
 
 static int dispatch_ioctl(struct client *client,