Revision 5d22fc25d4fc8096d2d7df27ea1893d4e055e764 authored by Linus Torvalds on 27 May 2016, 22:57:31 UTC, committed by Linus Torvalds on 27 May 2016, 22:57:31 UTC
The do_brk() and vm_brk() return value was "unsigned long" and returned the starting address on success, and an error value on failure. The reasons are entirely historical, and go back to it basically behaving like the mmap() interface does. However, nobody actually wanted that interface, and it causes totally pointless IS_ERR_VALUE() confusion. What every single caller actually wants is just the simpler integer return of zero for success and negative error number on failure. So just convert to that much clearer and more common calling convention, and get rid of all the IS_ERR_VALUE() uses wrt vm_brk(). Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 287980e
iso-resources.c
/*
* 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;
}
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);
}
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;
}
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;
}
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;
}
}
/**
* 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;
}
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;
}
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);
}
EXPORT_SYMBOL(fw_iso_resources_free);
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