cregit-Linux how code gets into the kernel

Release 4.8 sound/firewire/iso-resources.c

Directory: sound/firewire
/*
 * isochronous resources helper functions
 *
 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
 * Licensed under the terms of the GNU General Public License, version 2.
 */

#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/export.h>
#include <linux/jiffies.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include "iso-resources.h"

/**
 * fw_iso_resources_init - initializes a &struct fw_iso_resources
 * @r: the resource manager to initialize
 * @unit: the device unit for which the resources will be needed
 *
 * If the device does not support all channel numbers, change @r->channels_mask
 * after calling this function.
 */

int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit) { r->channels_mask = ~0uLL; r->unit = unit; mutex_init(&r->mutex); r->allocated = false; return 0; }

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EXPORT_SYMBOL(fw_iso_resources_init); /** * fw_iso_resources_destroy - destroy a resource manager * @r: the resource manager that is no longer needed */
void fw_iso_resources_destroy(struct fw_iso_resources *r) { WARN_ON(r->allocated); mutex_destroy(&r->mutex); }

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EXPORT_SYMBOL(fw_iso_resources_destroy);
static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed) { unsigned int bytes, s400_bytes; /* iso packets have three header quadlets and quadlet-aligned payload */ bytes = 3 * 4 + ALIGN(max_payload_bytes, 4); /* convert to bandwidth units (quadlets at S1600 = bytes at S400) */ if (speed <= SCODE_400) s400_bytes = bytes * (1 << (SCODE_400 - speed)); else s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400)); return s400_bytes; }

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static int current_bandwidth_overhead(struct fw_card *card) { /* * Under the usual pessimistic assumption (cable length 4.5 m), the * isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or * 88.3 + N * 24.3 in bandwidth units. * * The calculation below tries to deduce N from the current gap count. * If the gap count has been optimized by measuring the actual packet * transmission time, this derived overhead should be near the actual * overhead as well. */ return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512; }

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static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card) { for (;;) { s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64(); if (delay <= 0) return 0; if (schedule_timeout_interruptible(delay) > 0) return -ERESTARTSYS; } }

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/** * fw_iso_resources_allocate - allocate isochronous channel and bandwidth * @r: the resource manager * @max_payload_bytes: the amount of data (including CIP headers) per packet * @speed: the speed (e.g., SCODE_400) at which the packets will be sent * * This function allocates one isochronous channel and enough bandwidth for the * specified packet size. * * Returns the channel number that the caller must use for streaming, or * a negative error code. Due to potentionally long delays, this function is * interruptible and can return -ERESTARTSYS. On success, the caller is * responsible for calling fw_iso_resources_update() on bus resets, and * fw_iso_resources_free() when the resources are not longer needed. */
int fw_iso_resources_allocate(struct fw_iso_resources *r, unsigned int max_payload_bytes, int speed) { struct fw_card *card = fw_parent_device(r->unit)->card; int bandwidth, channel, err; if (WARN_ON(r->allocated)) return -EBADFD; r->bandwidth = packet_bandwidth(max_payload_bytes, speed); retry_after_bus_reset: spin_lock_irq(&card->lock); r->generation = card->generation; r->bandwidth_overhead = current_bandwidth_overhead(card); spin_unlock_irq(&card->lock); err = wait_isoch_resource_delay_after_bus_reset(card); if (err < 0) return err; mutex_lock(&r->mutex); bandwidth = r->bandwidth + r->bandwidth_overhead; fw_iso_resource_manage(card, r->generation, r->channels_mask, &channel, &bandwidth, true); if (channel == -EAGAIN) { mutex_unlock(&r->mutex); goto retry_after_bus_reset; } if (channel >= 0) { r->channel = channel; r->allocated = true; } else { if (channel == -EBUSY) dev_err(&r->unit->device, "isochronous resources exhausted\n"); else dev_err(&r->unit->device, "isochronous resource allocation failed\n"); } mutex_unlock(&r->mutex); return channel; }

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EXPORT_SYMBOL(fw_iso_resources_allocate); /** * fw_iso_resources_update - update resource allocations after a bus reset * @r: the resource manager * * This function must be called from the driver's .update handler to reallocate * any resources that were allocated before the bus reset. It is safe to call * this function if no resources are currently allocated. * * Returns a negative error code on failure. If this happens, the caller must * stop streaming. */
int fw_iso_resources_update(struct fw_iso_resources *r) { struct fw_card *card = fw_parent_device(r->unit)->card; int bandwidth, channel; mutex_lock(&r->mutex); if (!r->allocated) { mutex_unlock(&r->mutex); return 0; } spin_lock_irq(&card->lock); r->generation = card->generation; r->bandwidth_overhead = current_bandwidth_overhead(card); spin_unlock_irq(&card->lock); bandwidth = r->bandwidth + r->bandwidth_overhead; fw_iso_resource_manage(card, r->generation, 1uLL << r->channel, &channel, &bandwidth, true); /* * When another bus reset happens, pretend that the allocation * succeeded; we will try again for the new generation later. */ if (channel < 0 && channel != -EAGAIN) { r->allocated = false; if (channel == -EBUSY) dev_err(&r->unit->device, "isochronous resources exhausted\n"); else dev_err(&r->unit->device, "isochronous resource allocation failed\n"); } mutex_unlock(&r->mutex); return channel; }

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EXPORT_SYMBOL(fw_iso_resources_update); /** * fw_iso_resources_free - frees allocated resources * @r: the resource manager * * This function deallocates the channel and bandwidth, if allocated. */
void fw_iso_resources_free(struct fw_iso_resources *r) { struct fw_card *card = fw_parent_device(r->unit)->card; int bandwidth, channel; mutex_lock(&r->mutex); if (r->allocated) { bandwidth = r->bandwidth + r->bandwidth_overhead; fw_iso_resource_manage(card, r->generation, 1uLL << r->channel, &channel, &bandwidth, false); if (channel < 0) dev_err(&r->unit->device, "isochronous resource deallocation failed\n"); r->allocated = false; } mutex_unlock(&r->mutex); }

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EXPORT_SYMBOL(fw_iso_resources_free);

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Directory: sound/firewire
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