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>
diff --git a/drivers/media/dvb/firewire/firedtv-avc.c b/drivers/media/dvb/firewire/firedtv-avc.c
index fc5ccd8..21c52e3 100644
--- a/drivers/media/dvb/firewire/firedtv-avc.c
+++ b/drivers/media/dvb/firewire/firedtv-avc.c
@@ -1320,14 +1320,10 @@
{
int ret;
- mutex_lock(&fdtv->avc_mutex);
-
ret = fdtv_read(fdtv, addr, data);
if (ret < 0)
dev_err(fdtv->device, "CMP: read I/O error\n");
- mutex_unlock(&fdtv->avc_mutex);
-
return ret;
}
@@ -1335,18 +1331,9 @@
{
int ret;
- mutex_lock(&fdtv->avc_mutex);
-
- /* data[] is stack-allocated and should not be DMA-mapped. */
- memcpy(fdtv->avc_data, data, 8);
-
- ret = fdtv_lock(fdtv, addr, fdtv->avc_data);
+ ret = fdtv_lock(fdtv, addr, data);
if (ret < 0)
dev_err(fdtv->device, "CMP: lock I/O error\n");
- else
- memcpy(data, fdtv->avc_data, 8);
-
- mutex_unlock(&fdtv->avc_mutex);
return ret;
}