diff options
| author | Stefan Richter <stefanr@s5r6.in-berlin.de> | 2011-04-22 15:13:54 +0200 |
|---|---|---|
| committer | Stefan Richter <stefanr@s5r6.in-berlin.de> | 2011-05-10 22:53:44 +0200 |
| commit | f30e6d3e419bfb5540fa82ba7eca01d578556e6b (patch) | |
| tree | e4d6e7bad161a76b09557bf7513358ae1ce8f7fb /drivers/firewire/core-transaction.c | |
| parent | 020abf03cd659388f94cb328e1e1df0656e0d7ff (diff) | |
| download | linux-f30e6d3e419bfb5540fa82ba7eca01d578556e6b.tar.bz2 | |
firewire: octlet AT payloads can be stack-allocated
We do not need slab allocations anymore in order to satisfy
streaming DMA mapping constraints, thanks to commit da28947e7e36
"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>
Diffstat (limited to 'drivers/firewire/core-transaction.c')
| -rw-r--r-- | drivers/firewire/core-transaction.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c index d00f8ce902cc..77275fdf6c1f 100644 --- a/drivers/firewire/core-transaction.c +++ b/drivers/firewire/core-transaction.c @@ -326,8 +326,8 @@ static int allocate_tlabel(struct fw_card *card) * It will contain tag, channel, and sy data instead of a node ID then. * * The payload buffer at @data is going to be DMA-mapped except in case of - * quadlet-sized payload or of local (loopback) requests. Hence make sure that - * the buffer complies with the restrictions for DMA-mapped memory. The + * @length <= 8 or of local (loopback) requests. Hence make sure that the + * buffer complies with the restrictions of the streaming DMA mapping API. * @payload must not be freed before the @callback is called. * * In case of request types without payload, @data is NULL and @length is 0. @@ -411,7 +411,8 @@ static void transaction_callback(struct fw_card *card, int rcode, * * Returns the RCODE. See fw_send_request() for parameter documentation. * Unlike fw_send_request(), @data points to the payload of the request or/and - * to the payload of the response. + * to the payload of the response. DMA mapping restrictions apply to outbound + * request payloads of >= 8 bytes but not to inbound response payloads. */ int fw_run_transaction(struct fw_card *card, int tcode, int destination_id, int generation, int speed, unsigned long long offset, |