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firewire: cdev: add PHY packet reception

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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>
This commit is contained in:
Stefan Richter
2010-07-16 22:25:51 +02:00
parent 850bb6f23b
commit bf54e1462b
7 changed files with 111 additions and 15 deletions
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2
drivers/firewire/core.h
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@ -128,6 +128,7 @@ extern const struct file_operations fw_device_ops;
void fw_device_cdev_update(struct fw_device *device);
void fw_device_cdev_remove(struct fw_device *device);
void fw_cdev_handle_phy_packet(struct fw_card *card, struct fw_packet *p);
/* -device */
@ -214,6 +215,7 @@ static inline bool is_next_generation(int new_generation, int old_generation)
#define TCODE_IS_READ_REQUEST(tcode) (((tcode) & ~1) == 4)
#define TCODE_IS_BLOCK_PACKET(tcode) (((tcode) & 1) != 0)
#define TCODE_IS_LINK_INTERNAL(tcode) ((tcode) == 0xe)
#define TCODE_IS_REQUEST(tcode) (((tcode) & 2) == 0)
#define TCODE_IS_RESPONSE(tcode) (((tcode) & 2) != 0)
#define TCODE_HAS_REQUEST_DATA(tcode) (((tcode) & 12) != 4)