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>

1 files changed, 11 insertions, 10 deletions

diff --git a/drivers/firewire/core-iso.c b/drivers/firewire/core-iso.c
index 481056df9268..f872ede5af37 100644
--- a/drivers/firewire/core-iso.c
+++ b/drivers/firewire/core-iso.c
@@ -196,9 +196,10 @@ EXPORT_SYMBOL(fw_iso_context_stop);
  */
 
 static int manage_bandwidth(struct fw_card *card, int irm_id, int generation,
-                            int bandwidth, bool allocate, __be32 data[2])
+                            int bandwidth, bool allocate)
 {
         int try, new, old = allocate ? BANDWIDTH_AVAILABLE_INITIAL : 0;
+        __be32 data[2];
 
         /*
          * On a 1394a IRM with low contention, try < 1 is enough.
@@ -233,9 +234,10 @@ static int manage_bandwidth(struct fw_card *card, int irm_id, int generation,
 }
 
 static int manage_channel(struct fw_card *card, int irm_id, int generation,
-                u32 channels_mask, u64 offset, bool allocate, __be32 data[2])
+                u32 channels_mask, u64 offset, bool allocate)
 {
         __be32 bit, all, old;
+        __be32 data[2];
         int channel, ret = -EIO, retry = 5;
 
         old = all = allocate ? cpu_to_be32(~0) : 0;
@@ -284,7 +286,7 @@ static int manage_channel(struct fw_card *card, int irm_id, int generation,
 }
 
 static void deallocate_channel(struct fw_card *card, int irm_id,
-                               int generation, int channel, __be32 buffer[2])
+                               int generation, int channel)
 {
         u32 mask;
         u64 offset;
@@ -293,7 +295,7 @@ static void deallocate_channel(struct fw_card *card, int irm_id,
         offset = channel < 32 ? CSR_REGISTER_BASE + CSR_CHANNELS_AVAILABLE_HI :
                                 CSR_REGISTER_BASE + CSR_CHANNELS_AVAILABLE_LO;
 
-        manage_channel(card, irm_id, generation, mask, offset, false, buffer);
+        manage_channel(card, irm_id, generation, mask, offset, false);
 }
 
 /**
@@ -322,7 +324,7 @@ static void deallocate_channel(struct fw_card *card, int irm_id,
  */
 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)
 {
         u32 channels_hi = channels_mask;        /* channels 31...0 */
         u32 channels_lo = channels_mask >> 32;  /* channels 63...32 */
@@ -335,11 +337,11 @@ void fw_iso_resource_manage(struct fw_card *card, int generation,
         if (channels_hi)
                 c = manage_channel(card, irm_id, generation, channels_hi,
                                 CSR_REGISTER_BASE + CSR_CHANNELS_AVAILABLE_HI,
-                                allocate, buffer);
+                                allocate);
         if (channels_lo && c < 0) {
                 c = manage_channel(card, irm_id, generation, channels_lo,
                                 CSR_REGISTER_BASE + CSR_CHANNELS_AVAILABLE_LO,
-                                allocate, buffer);
+                                allocate);
                 if (c >= 0)
                         c += 32;
         }
@@ -351,14 +353,13 @@ void fw_iso_resource_manage(struct fw_card *card, int generation,
         if (*bandwidth == 0)
                 return;
 
-        ret = manage_bandwidth(card, irm_id, generation, *bandwidth,
-                               allocate, buffer);
+        ret = manage_bandwidth(card, irm_id, generation, *bandwidth, allocate);
         if (ret < 0)
                 *bandwidth = 0;
 
         if (allocate && ret < 0) {
                 if (c >= 0)
-                        deallocate_channel(card, irm_id, generation, c, buffer);
+                        deallocate_channel(card, irm_id, generation, c);
                 *channel = ret;
         }
 }