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firewire: octlet AT payloads can be stack-allocated

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We do not need slab allocations anymore in order to satisfy
streaming DMA mapping constraints, thanks to commit da28947e7e
"firewire: ohci: avoid separate DMA mapping for small AT payloads".

(Besides, the slab-allocated buffers that firewire-core, firewire-sbp2,
and firedtv used to provide for 8-byte write and lock requests were
still not fully portable since they crossed cacheline boundaries or
shared a cacheline with unrelated CPU-accessed data.  snd-firewire-lib
got this aspect right by using an extra kmalloc/ kfree just for the
8-byte transaction buffer.)

This change replaces kmalloc'ed lock transaction scratch buffers in
firewire-core, firedtv, and snd-firewire-lib by local stack allocations.
Perhaps the most notable result of the change is simpler locking because
there is no need to serialize usages of preallocated per-device buffers
anymore.  Also, allocations and deallocations are simpler.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
This commit is contained in:
Stefan Richter 2011-04-22 15:13:54 +02:00
parent 020abf03cd
commit f30e6d3e41
9 changed files with 30 additions and 52 deletions
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3
include/linux/firewire.h
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@ -125,7 +125,6 @@ struct fw_card {
struct delayed_work bm_work; /* bus manager job */
int bm_retries;
int bm_generation;
__be32 bm_transaction_data[2];
int bm_node_id;
bool bm_abdicate;
@ -447,6 +446,6 @@ int fw_iso_context_stop(struct fw_iso_context *ctx);
void fw_iso_context_destroy(struct fw_iso_context *ctx);
void fw_iso_resource_manage(struct fw_card *card, int generation,
u64 channels_mask, int *channel, int *bandwidth,
bool allocate, __be32 buffer[2]);
bool allocate);
#endif /* _LINUX_FIREWIRE_H */