linux/sound/firewire/iso-resources.h
Stefan Richter f30e6d3e41 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 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>
2011-05-10 22:53:44 +02:00

38 lines
1.2 KiB
C

#ifndef SOUND_FIREWIRE_ISO_RESOURCES_H_INCLUDED
#define SOUND_FIREWIRE_ISO_RESOURCES_H_INCLUDED
#include <linux/mutex.h>
#include <linux/types.h>
struct fw_unit;
/**
* struct fw_iso_resources - manages channel/bandwidth allocation
* @channels_mask: if the device does not support all channel numbers, set this
* bit mask to something else than the default (all ones)
*
* This structure manages (de)allocation of isochronous resources (channel and
* bandwidth) for one isochronous stream.
*/
struct fw_iso_resources {
u64 channels_mask;
/* private: */
struct fw_unit *unit;
struct mutex mutex;
unsigned int channel;
unsigned int bandwidth; /* in bandwidth units, without overhead */
unsigned int bandwidth_overhead;
int generation; /* in which allocation is valid */
bool allocated;
};
int fw_iso_resources_init(struct fw_iso_resources *r,
struct fw_unit *unit);
void fw_iso_resources_destroy(struct fw_iso_resources *r);
int fw_iso_resources_allocate(struct fw_iso_resources *r,
unsigned int max_payload_bytes, int speed);
int fw_iso_resources_update(struct fw_iso_resources *r);
void fw_iso_resources_free(struct fw_iso_resources *r);
#endif