• S
    firewire: octlet AT payloads can be stack-allocated · f30e6d3e
    Stefan Richter 提交于
    We do not need slab allocations anymore in order to satisfy
    streaming DMA mapping constraints, thanks to commit da28947e
    "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: NStefan Richter <stefanr@s5r6.in-berlin.de>
    Acked-by: NClemens Ladisch <clemens@ladisch.de>
    f30e6d3e
iso-resources.h 1.2 KB
#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
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