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>

2 files changed, 34 insertions, 8 deletions

diff --git a/include/linux/firewire-cdev.h b/include/linux/firewire-cdev.h
index 5bc051b9a01..b8740916079 100644
--- a/include/linux/firewire-cdev.h
+++ b/include/linux/firewire-cdev.h
@@ -35,6 +35,7 @@
 /* available since kernel version 2.6.36 */
 #define FW_CDEV_EVENT_REQUEST2			0x06
 #define FW_CDEV_EVENT_PHY_PACKET_SENT		0x07
+#define FW_CDEV_EVENT_PHY_PACKET_RECEIVED	0x08
 
 /**
  * struct fw_cdev_event_common - Common part of all fw_cdev_event_ types
@@ -285,16 +286,24 @@ struct fw_cdev_event_iso_resource {
 };
 
 /**
- * struct fw_cdev_event_phy_packet - A PHY packet was transmitted
- * @closure:	See &fw_cdev_event_common;
- *		set by %FW_CDEV_IOC_SEND_PHY_PACKET ioctl
- * @type:	%FW_CDEV_EVENT_PHY_PACKET_SENT
+ * struct fw_cdev_event_phy_packet - A PHY packet was transmitted or received
+ * @closure:	See &fw_cdev_event_common; set by %FW_CDEV_IOC_SEND_PHY_PACKET
+ *		or %FW_CDEV_IOC_RECEIVE_PHY_PACKETS ioctl
+ * @type:	%FW_CDEV_EVENT_PHY_PACKET_SENT or %..._RECEIVED
  * @rcode:	%RCODE_..., indicates success or failure of transmission
+ * @length:	Data length in bytes
+ * @data:	Incoming data
+ *
+ * If @type is %FW_CDEV_EVENT_PHY_PACKET_SENT, @length is 0 and @data empty.
+ * If @type is %FW_CDEV_EVENT_PHY_PACKET_RECEIVED, @length is 8 and @data
+ * consists of the two PHY packet quadlets, in host byte order.
  */
 struct fw_cdev_event_phy_packet {
 	__u64 closure;
 	__u32 type;
 	__u32 rcode;
+	__u32 length;
+	__u32 data[0];
 };
 
 /**
@@ -308,7 +317,9 @@ struct fw_cdev_event_phy_packet {
  * @iso_resource:  Valid if @common.type ==
  *				%FW_CDEV_EVENT_ISO_RESOURCE_ALLOCATED or
  *				%FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED
- * @phy_packet:    Valid if @common.type == %FW_CDEV_EVENT_PHY_PACKET_SENT
+ * @phy_packet:    Valid if @common.type ==
+ *				%FW_CDEV_EVENT_PHY_PACKET_SENT or
+ *				%FW_CDEV_EVENT_PHY_PACKET_RECEIVED
  *
  * Convenience union for userspace use.  Events could be read(2) into an
  * appropriately aligned char buffer and then cast to this union for further
@@ -360,6 +371,7 @@ union fw_cdev_event {
 
 /* available since kernel version 2.6.36 */
 #define FW_CDEV_IOC_SEND_PHY_PACKET    _IOWR('#', 0x15, struct fw_cdev_send_phy_packet)
+#define FW_CDEV_IOC_RECEIVE_PHY_PACKETS _IOW('#', 0x16, struct fw_cdev_receive_phy_packets)
 
 /*
  * ABI version history
@@ -376,9 +388,9 @@ union fw_cdev_event {
  *               - shared use and auto-response for FCP registers
  *  3  (2.6.34)  - made &fw_cdev_get_cycle_timer reliable
  *               - added %FW_CDEV_IOC_GET_CYCLE_TIMER2
- *  4  (2.6.36)  - added %FW_CDEV_EVENT_REQUEST2, %FW_CDEV_EVENT_PHY_PACKET_SENT
+ *  4  (2.6.36)  - added %FW_CDEV_EVENT_REQUEST2, %FW_CDEV_EVENT_PHY_PACKET_*
  *               - implemented &fw_cdev_event_bus_reset.bm_node_id
- *               - added %FW_CDEV_IOC_SEND_PHY_PACKET
+ *               - added %FW_CDEV_IOC_SEND_PHY_PACKET, _RECEIVE_PHY_PACKETS
  */
 #define FW_CDEV_VERSION 3 /* Meaningless; don't use this macro. */
 
@@ -850,4 +862,17 @@ struct fw_cdev_send_phy_packet {
 	__u32 generation;
 };
 
+/**
+ * struct fw_cdev_receive_phy_packets - start reception of PHY packets
+ * @closure: Passed back to userspace in phy packet events
+ *
+ * This ioctl activates issuing of %FW_CDEV_EVENT_PHY_PACKET_RECEIVED due to
+ * incoming PHY packets from any node on the same bus as the device.
+ *
+ * The ioctl is only permitted on device files which represent a local node.
+ */
+struct fw_cdev_receive_phy_packets {
+	__u64 closure;
+};
+
 #endif /* _LINUX_FIREWIRE_CDEV_H */
diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index 0c38b8e9772..d974aa4a24c 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -111,9 +111,10 @@ struct fw_card {
 	bool beta_repeaters_present;
 
 	int index;
-
 	struct list_head link;
 
+	struct list_head phy_receiver_list;
+
 	struct delayed_work br_work; /* bus reset job */
 	bool br_short;