Follow up on commit c285f6ff6787 "firewire: remove global lock around
address handlers, convert to RCU":

  - address_handler_lock no longer serializes the address handler, only
    its function to serialize updates to the list of handlers remains.
    Rename the lock to address_handler_list_lock.

  - Callers of fw_core_remove_address_handler() must be able to sleep.
    Comment on this in the API documentation.

  - The counterpart fw_core_add_address_handler() is by nature something
    which is used in process context.  Replace spin_lock_bh() by
    spin_lock() in fw_core_add_address_handler() and in
    fw_core_remove_address_handler(), and document that process context
    is now required for fw_core_add_address_handler().

  - Extend the documentation of fw_address_callback_t.

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

Upper-layer handlers for inbound requests were called with a spinlock
held by firewire-core.  Calling into upper layers with a lower layer
lock held is generally a bad idea.

What's more, since commit ea102d0ec475 "firewire: core: convert AR-req
handler lock from _irqsave to _bh", a caller of fw_send_request() i.e.
initiator of outbound request could no longer do that while having
interrupts disabled, if the local node was addressed by that request.

In order to make all this more flexible, convert the management of
address ranges and handlers from a global lock around readers and
writers to RCU (and a remaining global lock for writers).  As a minor
side effect, handling of inbound requests at different cards and of
local requests is now no longer serialized.  (There is still per-card
serialization of remote requests since firewire-ohci uses a single DMA
tasklet for inbound request events.)

In other words, address handlers are now called in an RCU read-side
critical section instead of from within a spin_lock_bh serialized
section.

(Changelog rewritten by Stefan R.)

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

Pull firewire updates from Stefan Richter:

 - Small fixes and optimizations.

 - A new sysfs attribute to tell local and remote nodes apart.
   Useful to set special permissions/ ownership of local nodes'
   /dev/fw*, to start daemons on them (for diagnostics, management,
   AV targets, VersaPHY initiator or targets...), to pick up their
   GUID to use it as GUID of an SBP2 target instance, and of course
   for informational purposes.

* tag 'firewire-updates' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394:
  firewire: core: document is_local sysfs attribute
  firewire: core: add is_local sysfs device attribute
  firewire: ohci: initialize multiChanMode bits after reset
  firewire: core: fix multichannel IR with buffers larger than 2 GB
  firewire: ohci: sanity-check MMIO resource
  firewire: ohci: lazy bus time initialization
  firewire: core: allocate the low memory region
  firewire: core: make address handler length 64 bits

Prevent userspace applications from allocating low memory address
ranges.  Otherwise, if some application happens to allocate such
a range and intends for a remote node to access it, and if that node
also implements SBP-2 (which will become more likely with the upcoming
SBP-2 target support), these accesses would be routed by the physical
DMA unit to some wrong memory address.

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

Pull IEEE 1394 (FireWire) subsystem updates from Stefan Richter:

 - Fix mismatch between DMA mapping direction (was wrong) and DMA
   synchronization direction (was correct) of isochronous reception
   buffers of userspace drivers if vma-mapped for R/W access.  For
   example, libdc1394 was affected.

 - more consistent retry stategy in device discovery/ rediscovery, and
   improved failure diagnostics

 - various small cleanups, e.g. use SCSI layer's DMA mapping API in
   firewire-sbp2

* tag 'firewire-updates' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394:
  firewire: sbp2: document the absence of alignment requirements
  firewire: sbp2: remove superfluous blk_queue_max_segment_size() call
  firewire: sbp2: use scsi_dma_(un)map
  firewire: sbp2: give correct DMA device to scsi framework
  firewire: core: fw_device_refresh(): clean up error handling
  firewire: core: log config rom reading errors
  firewire: core: log error in case of failed bus manager lock
  firewire: move rcode_string() to core
  firewire: core: improve reread_config_rom() interface
  firewire: core: wait for inaccessible devices after bus reset
  firewire: ohci: omit spinlock IRQ flags where possible
  firewire: ohci: correct signedness of a local variable
  firewire: core: fix DMA mapping direction
  firewire: use module_pci_driver

Sometimes it's useful to know the FireWire speed of the request that has
just come in to a fw_address_handler callback. As struct fw_request is
opaque we can't peek inside to get the speed out of the struct fw_packet
that's just inside. For example, the SBP-2 spec says:

"The speed at which the block write request to the MANAGEMENT_AGENT
register is received shall determine the speed used by the target for
all subsequent requests to read the initiator’s configuration ROM, fetch
ORB’s from initiator memory or store status at the initiator’s
status_FIFO. Command block ORB’s separately specify the speed for
requests addressed to the data buffer or page table."

[ ANSI T10/1155D Revision 4 page 53/54 ]

Signed-off-by: Chris Boot <bootc@bootc.net>
Acked-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

There is nothing audio-specific about the rcode_string() helper, so move
it from snd-firewire-lib into firewire-core to allow other code to use it.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (fixed sound/firewire/cmp.c)

fw_core_handle_request() is called by the low-level driver in tasklet
context or process context, and fw_core_add/remove_address_handler() is
called by mid- or high-level code in process context.  So convert
address_handler_lock accesses from those which disable local IRQs to
ones which just disable local softIRQs.

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

Fix the following unlikely but possible race:

CPU 1                             CPU 2
------------------------------------------------------------------------
AR-request tasklet
    lookup handler
                                  unregister handler
				  free handler->callback_data or handler
    call handler->callback

The application which registered the handler has no way to stop nodes
sending new requests to their address range, hence cannot prevent this
race.

Fix it simply by extending the address_handler_lock-protected region
from only around the lookup to around both lookup and call.  We only
need to do so in the exclusive region handler; the FCP region handler
already holds the lock around the handler->callback call.

Alas this removes the current ability to execute the callback in
parallel on different CPUs if it was called for different FireWire cards
at the same time.  (For a single card, the handler is already
serialized.)  If this loss of a rather obscure feature is not tolerable,
a more complex fix would be required:  Add a handler reference counter;
wait in fw_core_remove_address_handler() for this conter to become zero.

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

Target-like applications or peer-to-peer-like applications require the
global address handler registration which we have right now, or a per-
card registration.  And node lookup, while it would be nice to have,
would be impossible in the brief time between self-ID-complete event and
completion of firewire-core's topology scanning.

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