firewire: cdev: add PHY packet reception

Add an FW_CDEV_IOC_RECEIVE_PHY_PACKETS ioctl() and
FW_CDEV_EVENT_PHY_PACKET_RECEIVED poll()/read() event for /dev/fw*.
This can be used to get information from remote PHYs by remote access
PHY packets.

This is also the 2nd half of the functionality (the receive part) to
support a userspace implementation of a VersaPHY transaction layer.

Safety considerations:

  - PHY packets are generally broadcasts, hence some kind of elevated
    privileges should be required of a process to be able to listen in
    on 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.

Other limitations:

  - PHY packet reception may be switched on by ioctl() but cannot be
    switched off again.  It would be trivial to provide an off switch,
    but this is not worth the code.  The client should simply close()
    the fd then, or just ignore further events.

  - For sake of simplicity of API and kernel-side implementation, no
    filter per packet content is provided.

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

1 files changed, 68 insertions, 5 deletions

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index f957199..0425dd5 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -69,6 +69,9 @@ struct client {
 	struct fw_iso_buffer buffer;
 	unsigned long vm_start;
 
+	struct list_head phy_receiver_link;
+	u64 phy_receiver_closure;
+
 	struct list_head link;
 	struct kref kref;
 };
@@ -201,6 +204,11 @@ struct outbound_phy_packet_event {
 	struct fw_cdev_event_phy_packet phy_packet;
 };
 
+struct inbound_phy_packet_event {
+	struct event event;
+	struct fw_cdev_event_phy_packet phy_packet;
+};
+
 static inline void __user *u64_to_uptr(__u64 value)
 {
 	return (void __user *)(unsigned long)value;
@@ -236,6 +244,7 @@ static int fw_device_op_open(struct inode *inode, struct file *file)
 	idr_init(&client->resource_idr);
 	INIT_LIST_HEAD(&client->event_list);
 	init_waitqueue_head(&client->wait);
+	INIT_LIST_HEAD(&client->phy_receiver_link);
 	kref_init(&client->kref);
 
 	file->private_data = client;
@@ -357,7 +366,7 @@ static void queue_bus_reset_event(struct client *client)
 
 	e = kzalloc(sizeof(*e), GFP_KERNEL);
 	if (e == NULL) {
-		fw_notify("Out of memory when allocating bus reset event\n");
+		fw_notify("Out of memory when allocating event\n");
 		return;
 	}
 
@@ -404,6 +413,7 @@ union ioctl_arg {
 	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;
+	struct fw_cdev_receive_phy_packets	receive_phy_packets;
 };
 
 static int ioctl_get_info(struct client *client, union ioctl_arg *arg)
@@ -671,9 +681,10 @@ static void handle_request(struct fw_card *card, struct fw_request *request,
 
 	r = kmalloc(sizeof(*r), GFP_ATOMIC);
 	e = kmalloc(sizeof(*e), GFP_ATOMIC);
-	if (r == NULL || e == NULL)
+	if (r == NULL || e == NULL) {
+		fw_notify("Out of memory when allocating event\n");
 		goto failed;
-
+	}
 	r->card    = card;
 	r->request = request;
 	r->data    = payload;
@@ -902,9 +913,10 @@ static void iso_callback(struct fw_iso_context *context, u32 cycle,
 	struct iso_interrupt_event *e;
 
 	e = kmalloc(sizeof(*e) + header_length, GFP_ATOMIC);
-	if (e == NULL)
+	if (e == NULL) {
+		fw_notify("Out of memory when allocating event\n");
 		return;
-
+	}
 	e->interrupt.type      = FW_CDEV_EVENT_ISO_INTERRUPT;
 	e->interrupt.closure   = client->iso_closure;
 	e->interrupt.cycle     = cycle;
@@ -1447,6 +1459,52 @@ static int ioctl_send_phy_packet(struct client *client, union ioctl_arg *arg)
 	return 0;
 }
 
+static int ioctl_receive_phy_packets(struct client *client, union ioctl_arg *arg)
+{
+	struct fw_cdev_receive_phy_packets *a = &arg->receive_phy_packets;
+	struct fw_card *card = client->device->card;
+
+	/* Access policy: Allow this ioctl only on local nodes' device files. */
+	if (!client->device->is_local)
+		return -ENOSYS;
+
+	spin_lock_irq(&card->lock);
+
+	list_move_tail(&client->phy_receiver_link, &card->phy_receiver_list);
+	client->phy_receiver_closure = a->closure;
+
+	spin_unlock_irq(&card->lock);
+
+	return 0;
+}
+
+void fw_cdev_handle_phy_packet(struct fw_card *card, struct fw_packet *p)
+{
+	struct client *client;
+	struct inbound_phy_packet_event *e;
+	unsigned long flags;
+
+	spin_lock_irqsave(&card->lock, flags);
+
+	list_for_each_entry(client, &card->phy_receiver_list, phy_receiver_link) {
+		e = kmalloc(sizeof(*e) + 8, GFP_ATOMIC);
+		if (e == NULL) {
+			fw_notify("Out of memory when allocating event\n");
+			break;
+		}
+		e->phy_packet.closure	= client->phy_receiver_closure;
+		e->phy_packet.type	= FW_CDEV_EVENT_PHY_PACKET_RECEIVED;
+		e->phy_packet.rcode	= RCODE_COMPLETE;
+		e->phy_packet.length	= 8;
+		e->phy_packet.data[0]	= p->header[1];
+		e->phy_packet.data[1]	= p->header[2];
+		queue_event(client, &e->event,
+			    &e->phy_packet, sizeof(e->phy_packet) + 8, NULL, 0);
+	}
+
+	spin_unlock_irqrestore(&card->lock, flags);
+}
+
 static int (* const ioctl_handlers[])(struct client *, union ioctl_arg *) = {
 	[0x00] = ioctl_get_info,
 	[0x01] = ioctl_send_request,
@@ -1470,6 +1528,7 @@ static int (* const ioctl_handlers[])(struct client *, union ioctl_arg *) = {
 	[0x13] = ioctl_send_stream_packet,
 	[0x14] = ioctl_get_cycle_timer2,
 	[0x15] = ioctl_send_phy_packet,
+	[0x16] = ioctl_receive_phy_packets,
 };
 
 static int dispatch_ioctl(struct client *client,
@@ -1577,6 +1636,10 @@ static int fw_device_op_release(struct inode *inode, struct file *file)
 	struct client *client = file->private_data;
 	struct event *event, *next_event;
 
+	spin_lock_irq(&client->device->card->lock);
+	list_del(&client->phy_receiver_link);
+	spin_unlock_irq(&client->device->card->lock);
+
 	mutex_lock(&client->device->client_list_mutex);
 	list_del(&client->link);
 	mutex_unlock(&client->device->client_list_mutex);