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path: root/drivers/firewire
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2009-07-06Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6: ieee1394: sbp2: add support for disks >2 TB (and 16 bytes long CDBs) firewire: sbp2: add support for disks >2 TB (and 16 bytes long CDBs) firewire: core: do not DMA-map stack addresses
2009-07-02firewire: sbp2: add support for disks >2 TB (and 16 bytes long CDBs)Stefan Richter
Increase the command ORB data structure to transport up to 16 bytes long CDBs (instead of 12 bytes), and tell the SCSI mid layer about it. This is notably necessary for READ CAPACITY(16) and friends, i.e. support of large disks. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-25firewire: core: do not DMA-map stack addressesStefan Richter
The DMA mapping API cannot map on-stack addresses, as explained in Documentation/DMA-mapping.txt. Convert the two cases of on-stack packet payload buffers in firewire-core (payload of lock requests in the bus manager work and in iso resource management) to slab-allocated memory. There are a number on-stack buffers for quadlet write or quadlet read requests in firewire-core and firewire-sbp2. These are harmless; they are copied to/ from card driver internal DMA buffers since quadlet payloads are inlined with packet headers. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-22Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6: firewire: new stack is no longer experimental firewire: net: better FIFO address range check and rcodes firewire: net: fix card driver reloading firewire: core: fix iso context shutdown on card removal firewire: core: fix DMA unmapping in iso buffer removal firewire: net: adjust net_device ops firewire: net: remove unused code firewire: net: allow for unordered unit discovery firewire: net: style changes firewire: net: add Kconfig item, rename driver firewire: add IPv4 support
2009-06-21firewire: new stack is no longer experimentalStefan Richter
The new stack is now recommended over the old one if used for industrial video (IIDC/DCAM) or for storage devices (SBP-2) due to better performance, improved compatibility, added features, and security. It should also be functionally on par with and is more secure than the old ieee1394 stack in the use case of consumer video devices. IP-over-1394 support for the new stack is currently emerging, and a backend of the firedtv DVB driver to the new stack should be available soon. The one remaining area where the old stack is still required are audio devices, as the new stack is not yet able to support the FFADO FireWire audio framework. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-16Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6: firewire: core: use more outbound tlabels firewire: core: don't update Broadcast_Channel if RFC 2734 conditions aren't met firewire: core: prepare for non-core children of card devices firewire: core: include linux/uaccess.h instead of asm/uaccess.h firewire: add parent-of-unit accessor firewire: rename source files firewire: reorganize header files firewire: clean up includes firewire: ohci: access bus_seconds atomically firewire: also use vendor ID in root directory for driver matches firewire: share device ID table type with ieee1394 firewire: core: add sysfs attribute for easier udev rules firewire: core: check for missing struct update at build time, not run time firewire: core: improve check for local node
2009-06-16firewire: net: better FIFO address range check and rcodesStefan Richter
The AR req handler should not check the generation; higher level code is the better place to handle bus generation changes. The target node ID just needs to be checked for not being the "all nodes" address; in this case don't handle the request and don't respond. Use Address_Error and Type_Error rcodes as appropriate. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-16firewire: net: fix card driver reloadingStefan Richter
Fix some problems from "firewire: net: allow for unordered unit discovery": - fwnet_remove was missing a list_del, causing fwnet_probe to crash if called after fwnet_remove, e.g. if firewire-ohci was unloaded and reloaded. - fwnet_probe should set its new_netdev flag only if it actually allocated a net_device. - Use dev_set_drvdata and dev_get_drvdata instead of deprecated direct access to device.driver_data. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-16firewire: core: fix iso context shutdown on card removalStefan Richter
If isochronous contexts existed when firewire-ohci was unloaded, the core iso shutdown functions crashed with NULL dereferences, and buffers etc. weren't released. How the fix works: We first copy the card driver's iso shutdown hooks into the dummy driver, then fw_destroy_nodes notifies upper layers of devices going away, these should shut down (including their iso contexts), wait_for_completion(&card->done) will be triggered after upper layers gave up all fw_device references, after which the card driver's shutdown proceeds. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-16firewire: core: fix DMA unmapping in iso buffer removalStefan Richter
dmap_unmap_page() shall use the same direction as dma_map_page(). Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-15firewire: remove driver_data direct access of struct deviceGreg Kroah-Hartman
In the near future, the driver core is going to not allow direct access to the driver_data pointer in struct device. Instead, the functions dev_get_drvdata() and dev_set_drvdata() should be used. These functions have been around since the beginning, so are backwards compatible with all older kernel versions. Cc: linux1394-devel@lists.sourceforge.net Acked-by: Stefan Richter <stefanr@s5r6.in-berlin.de> Cc: Kristian Hoegsberg <krh@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-14firewire: net: adjust net_device opsStefan Richter
The .ndo_tx_timeout callback is currently without function; delete it. Give .watchdog_timeo a proper time value; lower it to 2 seconds. Decrease the .tx_queue_len from 1000 (as in Ethernet card drivers) to 10 because we have only 64 transaction labels available, and responders might have further limits of their AR req contexts. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-14firewire: net: remove unused codeStefan Richter
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-14firewire: net: allow for unordered unit discoveryStefan Richter
Decouple the creation and destruction of the net_device from the order of discovery and removal of nodes with RFC 2734 unit directories since there is no reliable order. The net_device is now created when the first RFC 2734 unit on a card is discovered, and destroyed when the last RFC 2734 unit on a card went away. This includes all remote units as well as the local unit, which is therefore tracked as a peer now too. Also, locking around the list of peers is slightly extended to guard against peer removal. As a side effect, fwnet_peer.pdg_lock has become superfluous and is deleted. Peer data (max_rec, speed, node ID, generation) are updated more carefully. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-14firewire: net: style changesStefan Richter
Change names of types, variables, functions. Omit debug code. Use get_unaligned*, put_unaligned*. Annotate big endian data. Handle errors in __init. Change whitespace. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-14firewire: net: add Kconfig item, rename driverStefan Richter
The driver is now called firewire-net. It might implement the transport of other networking protocols in the future, notably IPv6 per RFC 3146. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-14firewire: add IPv4 supportJay Fenlason
Implement IPv4 over IEEE 1394 as per RFC 2734 for the newer firewire stack. This feature has only been present in the older ieee1394 stack via the eth1394 driver. Still to do: - fix ipv4_priv and ipv4_node lifetime logic - fix determination of speeds and max payloads - fix bus reset handling - fix unaligned memory accesses - fix coding style - further testing/ improvement of fragment reassembly - perhaps multicast support Signed-off-by: Jay Fenlason <fenlason@redhat.com> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (rebased, copyright note, changelog)
2009-06-14firewire: core: use more outbound tlabelsStefan Richter
Tlabel is a 6 bits wide datum. Wrap it after 63 rather than 31 for more safety against transaction label exhaustion and potential responders' transaction layer bugs. (As noted by Guus Sliepen, this change requires an expansion of tlabel_mask to 64 bits.) Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-14firewire: core: don't update Broadcast_Channel if RFC 2734 conditions aren't metStefan Richter
This extra check will avoid Broadcast_Channel register related traffic to many IIDC, SBP-2, and AV/C devices which aren't IRMC or have a max_rec < 8 (i.e. support < 512 bytes async payload). This avoids a little bit of traffic after bus reset and is even more careful with devices which don't implement this CSR. The assumption is that no other protocol than IP over 1394 uses the broadcast channel for streams. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-06firewire: core: prepare for non-core children of card devicesStefan Richter
The IP-over-1394 driver will add child devices beneath card devices which are not of type fw_device. Hence firewire-core's callbacks in device_for_each_child() and device_find_child() need to check for the device type now. Initial version written by Jay Fenlason. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-06firewire: core: include linux/uaccess.h instead of asm/uaccess.hStefan Richter
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-06firewire: add parent-of-unit accessorStefan Richter
Retrieval of an fw_unit's parent is a common pattern in high-level code. Wrap it up as device = fw_parent_device(unit). Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-05firewire: rename source filesStefan Richter
The source files of firewire-core, firewire-ohci, firewire-sbp2, i.e. "drivers/firewire/fw-*.c" are renamed to "drivers/firewire/core-*.c", "drivers/firewire/ohci.c", "drivers/firewire/sbp2.c". The old fw- prefix was redundant to the directory name. The new core- prefix distinguishes the files according to which driver they belong to. This change comes a little late, but still before further firewire drivers are added as anticipated RSN. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-05firewire: reorganize header filesStefan Richter
The three header files of firewire-core, i.e. "drivers/firewire/fw-device.h", "drivers/firewire/fw-topology.h", "drivers/firewire/fw-transaction.h", are replaced by "drivers/firewire/core.h", "include/linux/firewire.h". The latter includes everything which a firewire high-level driver (like firewire-sbp2) needs besides linux/firewire-constants.h, while core.h contains the rest which is needed by firewire-core itself and by low- level drivers (card drivers) like firewire-ohci. High-level drivers can now also reside outside of drivers/firewire without having to add drivers/firewire to the header file search path in makefiles. At least the firedtv driver will be such a driver. I also considered to spread the contents of core.h over several files, one for each .c file where the respective implementation resides. But it turned out that most core .c files will end up including most of the core .h files. Also, the combined core.h isn't unreasonably big, and it will lose more of its contents to linux/firewire.h anyway soon when more firewire drivers are added. (IP-over-1394, firedtv, and there are plans for one or two more.) Furthermore, fw-ohci.h is renamed to ohci.h. The name of core.h and ohci.h is chosen with regard to name changes of the .c files in a follow-up change. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-05firewire: clean up includesStefan Richter
Include required headers which were only indirectly included. Remove unused includes and an unused constant. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-05firewire: ohci: access bus_seconds atomicallyStefan Richter
In the unlikely event that card->driver->get_bus_time() is called during a cycle64Seconds interrupt, we could read garbage unless atomic accesses are used. The switch to atomic ops requires to change the 64 seconds counter from unsigned to signed, but this shouldn't matter to the end result. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-05firewire: also use vendor ID in root directory for driver matchesStefan Richter
Due to AV/C protocol extensions, FireDTV devices need a vendor-specific driver. But their configuration ROM features a vendor ID only in the root directory, not in the unit directory. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-05firewire: share device ID table type with ieee1394Stefan Richter
That way, the new firedtv driver will be able to use a single ID table in builds against ieee1394 core and/or against firewire core. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-01firewire: core: add sysfs attribute for easier udev rulesStefan Richter
This adds the attribute /sys/bus/firewire/devices/fw[0-9]+/units. It can be used in udev rules like the following ones: # IIDC devices: industrial cameras and some webcams SUBSYSTEM=="firewire", ATTR{units}=="*0x00a02d:0x00010?*", GROUP="video" # AV/C devices: camcorders, set-top boxes, TV sets, audio devices, ... SUBSYSTEM=="firewire", ATTR{units}=="*0x00a02d:0x010001*", GROUP="video" Background: firewire-core manages two device types: - fw_device is a FireWire node. A character device file is associated with it. - fw_unit is a unit directory on a node. Each fw_device may have 0..n children of type fw_unit. The units tell us what kinds of protocols a node implements. We want to set ownership or ACLs or permissions of the character device file of an fw_device, or/and create symlinks to it, based on available protocols. Until now udev rules had to look at the fw_unit devices and then modify their parent's character device file accordingly. This is problematic for two reasons: 1) It happens sometime after the creation of the fw_device, 2) an access policy may require that information from all children is evaluated before a decision about the parent is made. Problem 1) can ultimately not be avoided since this is the nature of FireWire nodes: They may add or remove unit directories at any point in time. However, we can still help userland a lot by providing the protocol type information of all units in a summary sysfs attribute directly at the fw_device. This way, - the information is immediately available at the affected device when userspace goes about to handle an ADD or CHANGE event of the fw_device, - with most policies, it won't be necessary anymore to dig through child attributes. The new attribute is called "units". It contains space-separated tuples of specifier_id and version of each present unit. The delimiter within tuples is a colon. Specifier_id and version are printed as 0x%06x. Here is an example of a node which implements an IPv4 unit and an IPv6 unit: $ cat /sys/bus/firewire/devices/fw2/units 0x00005e:0x000001 0x00005e:0x000002 Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-06-01firewire: core: check for missing struct update at build time, not run timeStefan Richter
struct fw_attribute_group.attrs.[] must have enough room for all attributes. This can and should be checked at build time. Our previous check at run time was a little late and not reliable since most of the time less than the available attributes are populated. Furthermore, omit an increment of an index at its last usage. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-05-17firewire: core: improve check for local nodeStefan Richter
My recently added test for a device being local in fw-cdev.c got it slightly wrong: Comparisons of node IDs are only valid if the generation is current, which I forgot to check. Normally, serialization by card->lock takes care of this, but a device in FW_DEVICE_GONE state will necessarily have a wrong generation and invalid node_id. The "is it local?" check is made 100% correct and simpler now by means of a struct fw_device flag which is set at fw_device creation. Besides the fw-cdev site which was to be fixed, there is another site which can make use of the new flag, and an RFC-2734 driver will benefit from it too. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: core: optimize propagation of BROADCAST_CHANNELStefan Richter
Cache the test result of whether a device implements BROADCAST_CHANNEL. This minimizes traffic on the bus after each bus reset. A majority of devices does not implement BROADCAST_CHANNEL. Remove busy retries; just rely on the hardware to retry requests to busy responders. Remove unnecessary log messages. Rename the flag is_irm to broadcast_channel_allocated to better reflect its meaning. Reset the flag earlier in fw_core_handle_bus_reset. Pass the generation down as a call parameter; that way generation can't be newer than card->broadcast_channel_allocated and device->node_id. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: core: simplify broadcast channel allocationStefan Richter
fw-iso.c has channel allocation code now, use it. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: core: increase bus manager grace periodStefan Richter
Per IEEE 1394 clause 8.4.2.5, bus manager capable nodes which are not incumbent shall wait at least 125ms before trying to establish themselves as bus manager. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: core: drop unused call parameters of close_transactionStefan Richter
All callers inserted NULL and 0 here. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: cdev: add closure to async stream ioctlStefan Richter
This changes the as yet unreleased FW_CDEV_IOC_SEND_STREAM_PACKET ioctl to generate an fw_cdev_event_response event just like the other two ioctls for asynchronous request transmission do. This way, clients get feedback on successful or unsuccessful transmission. This also adds input validation for length, tag, channel, sy, speed. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: cdev: simplify FW_CDEV_IOC_SEND_REQUEST return valueStefan Richter
This changes the ioctl() return value of FW_CDEV_IOC_SEND_REQUEST and of the as yet unreleased FW_CDEV_IOC_SEND_BROADCAST_REQUEST. They used to return sizeof(struct fw_cdev_send_request *) + data_length which is obviously a failed attempt to emulate the return value of raw1394's respective interface which uses write() instead of ioctl(). However, the first summand, as size of a kernel pointer, is entirely meaningless to clients and the second summand is already known to clients. And the result does not resemble raw1394's write() return code anyway. So simplify it to a constant non-negative value, i.e. 0. The only dangers here would be that future client implementations check for error by ret != 0 instead of ret < 0 when running on top of an old kernel; or that current clients interpret ret = 0 or more as failure. But both are hypothetical cases which don't justify to return irritating values. While we touch this code, also remove "& 0x1f" from tcode in the call of fw_send_request. The tcode cannot be bigger than 0x1f at this point. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: cdev: fix race of ioctl_send_request with bus resetStefan Richter
The bus reset handler concurrently frees client->device->node. Use device->node_id instead. This is equivalent to device->node->node_id while device->generation is current. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: cdev: secure add_descriptor ioctlStefan Richter
The access permissions and ownership or ACL of /dev/fw* character device files will typically be set based on the device type of the respective nodes, as obtained by firewire-core from descriptors in the device's configuration ROM. An example policy is to deny write permission by default but grant write permission to files of AV/C video and audio devices and IIDC video devices. The FW_CDEV_IOC_ADD_DESCRIPTOR ioctl could be used to partly subvert such a policy: Find a device file with relaxed permissions, use the ioctl to add a descriptor with AV/C marker to the local node's ROM, thus gain access to the local node's character device file. (This is only possible if there are udev scripts installed which actively relax permissions for known device types and if there is a device of such a type connected.) Accessibility of the local node's device file is relevant to host security if the host contains two or more IEEE 1394 link layer controllers which are plugged into a single bus. Therefore change the ABI to deny FW_CDEV_IOC_ADD_DESCRIPTOR if the file belongs to a remote node. (This change has no impact on known implementers of the ABI: None of them uses the ioctl yet.) Also clarify the documentation: The ioctl affects all local nodes, not just one local node. Cc: stable@kernel.org Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: cdev: amendment to "add ioctl to query maximum transmission speed"Stefan Richter
The as yet unreleased FW_CDEV_IOC_GET_SPEED ioctl puts only a single integer into the parameter buffer. We can use ioctl()'s return value instead. (Also: Some whitespace change in firewire-cdev.h.) Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: broadcast channel supportJay Fenlason
This patch adds the ISO broadcast channel support that is required of a 1394a IRM. In specific, if the local device the IRM, it allocates ISO channel 31 and sets the broadcast channel register of all devices on the local bus to BROADCAST_CHANNEL_INITIAL | BROADCAST_CHANNEL_VALID to indicate that channel 31 can be use for broadcast messages. One minor complication is that on startup the local device may become IRM before all the devices on the bus have been enumerated by the stack. Therefore we have to keep a "the local device is IRM" flag and possibly set the broadcast channel register of new devices at enumeration time. Signed-off-by: Jay Fenlason <fenlason@redhat.com> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: implement asynchronous stream transmissionJay Fenlason
Allow userspace and other firewire drivers (fw-ipv4 I'm looking at you!) to send Asynchronous Transmit Streams as described in 7.8.3 of release 1.1 of the 1394 Open Host Controller Interface Specification. Signed-off-by: Jay Fenlason <fenlason@redhat.com> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (tweaks)
2009-03-24firewire: core: normalize a function argument nameStefan Richter
It's called "payload" rather than "data" almost everywhere in fw-transaction.c. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: normalize a variable nameStefan Richter
Standardize on if (err) handle_error; and if (ret < 0) handle_error; Don't call a variable err if we store values in it which mean success. Also, offset some return statements by a blank line since this how we do it in drivers/firewire. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: core: remove condition which is always falseStefan Richter
reread_bus_info_block() only gets to see devices whose config_rom_length is at least 6 (ROM header, bus info block, root directory header). Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: core: move some functionsStefan Richter
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: core: clean up includesStefan Richter
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: cdev: simplify a schedule_delayed_work wrapperStefan Richter
The kernel API documentation says that queue_delayed_work() returns 0 (only) if the work was already queued. The return codes of schedule_delayed_work() are not documented but the same. In init_iso_resource(), the work has never been queued yet, hence we can assume schedule_delayed_work() to be a guaranteed success there. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: cdev: add ioctls for iso resource management, amendmentStefan Richter
Some fixes: - Remove stale documentation. - Fix a != vs. == thinko that got in the way of channel management. - Try bandwidth deallocation even if channel deallocation failed. A simplification: - fw_cdev_allocate_iso_resource.channels is now ordered like libdc1394's dc1394_iso_allocate_channel() channels_allowed argument. By the way, I looked closer at cards from NEC, TI, and VIA, and noticed that they all don't implement IEEE 1394a behaviour which is meant to deviate from IEEE 1212's notion of lock compare-swap. This means that we have to do two lock transactions instead of one in many cases where one transaction would already succeed on a fully 1394a compliant IRM. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
2009-03-24firewire: cdev: shut down iso context before freeing the bufferStefan Richter
DMA must be halted before we DMA-unmap and free the DMA buffer. Since we cannot rely on the client to stop the context before it closes the fd, we have to reorder fw_iso_buffer_destroy vs. fw_iso_context_destroy. Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>