diff options
Diffstat (limited to 'drivers/hwtracing/stm')
| -rw-r--r-- | drivers/hwtracing/stm/Kconfig | 15 | ||||
| -rw-r--r-- | drivers/hwtracing/stm/Makefile | 2 | ||||
| -rw-r--r-- | drivers/hwtracing/stm/core.c | 203 | ||||
| -rw-r--r-- | drivers/hwtracing/stm/dummy_stm.c | 67 | ||||
| -rw-r--r-- | drivers/hwtracing/stm/heartbeat.c | 126 | ||||
| -rw-r--r-- | drivers/hwtracing/stm/policy.c | 27 | ||||
| -rw-r--r-- | drivers/hwtracing/stm/stm.h | 2 |
7 files changed, 381 insertions, 61 deletions
diff --git a/drivers/hwtracing/stm/Kconfig b/drivers/hwtracing/stm/Kconfig index e7a348807f0c..847a39b35307 100644 --- a/drivers/hwtracing/stm/Kconfig +++ b/drivers/hwtracing/stm/Kconfig @@ -9,6 +9,8 @@ config STM Say Y here to enable System Trace Module device support. +if STM + config STM_DUMMY tristate "Dummy STM driver" help @@ -25,3 +27,16 @@ config STM_SOURCE_CONSOLE If you want to send kernel console messages over STM devices, say Y. + +config STM_SOURCE_HEARTBEAT + tristate "Heartbeat over STM devices" + help + This is a kernel space trace source that sends periodic + heartbeat messages to trace hosts over STM devices. It is + also useful for testing stm class drivers and the stm class + framework itself. + + If you want to send heartbeat messages over STM devices, + say Y. + +endif diff --git a/drivers/hwtracing/stm/Makefile b/drivers/hwtracing/stm/Makefile index f9312c38dd7a..a9ce3d487e57 100644 --- a/drivers/hwtracing/stm/Makefile +++ b/drivers/hwtracing/stm/Makefile @@ -5,5 +5,7 @@ stm_core-y := core.o policy.o obj-$(CONFIG_STM_DUMMY) += dummy_stm.o obj-$(CONFIG_STM_SOURCE_CONSOLE) += stm_console.o +obj-$(CONFIG_STM_SOURCE_HEARTBEAT) += stm_heartbeat.o stm_console-y := console.o +stm_heartbeat-y := heartbeat.o diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c index d2dff159a471..cb07713aceda 100644 --- a/drivers/hwtracing/stm/core.c +++ b/drivers/hwtracing/stm/core.c @@ -67,9 +67,24 @@ static ssize_t channels_show(struct device *dev, static DEVICE_ATTR_RO(channels); +static ssize_t hw_override_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct stm_device *stm = to_stm_device(dev); + int ret; + + ret = sprintf(buf, "%u\n", stm->data->hw_override); + + return ret; +} + +static DEVICE_ATTR_RO(hw_override); + static struct attribute *stm_attrs[] = { &dev_attr_masters.attr, &dev_attr_channels.attr, + &dev_attr_hw_override.attr, NULL, }; @@ -113,6 +128,7 @@ struct stm_device *stm_find_device(const char *buf) stm = to_stm_device(dev); if (!try_module_get(stm->owner)) { + /* matches class_find_device() above */ put_device(dev); return NULL; } @@ -125,7 +141,7 @@ struct stm_device *stm_find_device(const char *buf) * @stm: stm device, previously acquired by stm_find_device() * * This drops the module reference and device reference taken by - * stm_find_device(). + * stm_find_device() or stm_char_open(). */ void stm_put_device(struct stm_device *stm) { @@ -185,6 +201,9 @@ static void stm_output_claim(struct stm_device *stm, struct stm_output *output) { struct stp_master *master = stm_master(stm, output->master); + lockdep_assert_held(&stm->mc_lock); + lockdep_assert_held(&output->lock); + if (WARN_ON_ONCE(master->nr_free < output->nr_chans)) return; @@ -199,6 +218,9 @@ stm_output_disclaim(struct stm_device *stm, struct stm_output *output) { struct stp_master *master = stm_master(stm, output->master); + lockdep_assert_held(&stm->mc_lock); + lockdep_assert_held(&output->lock); + bitmap_release_region(&master->chan_map[0], output->channel, ilog2(output->nr_chans)); @@ -288,6 +310,7 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width, } spin_lock(&stm->mc_lock); + spin_lock(&output->lock); /* output is already assigned -- shouldn't happen */ if (WARN_ON_ONCE(output->nr_chans)) goto unlock; @@ -304,6 +327,7 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width, ret = 0; unlock: + spin_unlock(&output->lock); spin_unlock(&stm->mc_lock); return ret; @@ -312,11 +336,18 @@ unlock: static void stm_output_free(struct stm_device *stm, struct stm_output *output) { spin_lock(&stm->mc_lock); + spin_lock(&output->lock); if (output->nr_chans) stm_output_disclaim(stm, output); + spin_unlock(&output->lock); spin_unlock(&stm->mc_lock); } +static void stm_output_init(struct stm_output *output) +{ + spin_lock_init(&output->lock); +} + static int major_match(struct device *dev, const void *data) { unsigned int major = *(unsigned int *)data; @@ -339,6 +370,7 @@ static int stm_char_open(struct inode *inode, struct file *file) if (!stmf) return -ENOMEM; + stm_output_init(&stmf->output); stmf->stm = to_stm_device(dev); if (!try_module_get(stmf->stm->owner)) @@ -349,6 +381,8 @@ static int stm_char_open(struct inode *inode, struct file *file) return nonseekable_open(inode, file); err_free: + /* matches class_find_device() above */ + put_device(dev); kfree(stmf); return err; @@ -357,9 +391,19 @@ err_free: static int stm_char_release(struct inode *inode, struct file *file) { struct stm_file *stmf = file->private_data; + struct stm_device *stm = stmf->stm; + + if (stm->data->unlink) + stm->data->unlink(stm->data, stmf->output.master, + stmf->output.channel); + + stm_output_free(stm, &stmf->output); - stm_output_free(stmf->stm, &stmf->output); - stm_put_device(stmf->stm); + /* + * matches the stm_char_open()'s + * class_find_device() + try_module_get() + */ + stm_put_device(stm); kfree(stmf); return 0; @@ -380,8 +424,8 @@ static int stm_file_assign(struct stm_file *stmf, char *id, unsigned int width) return ret; } -static void stm_write(struct stm_data *data, unsigned int master, - unsigned int channel, const char *buf, size_t count) +static ssize_t stm_write(struct stm_data *data, unsigned int master, + unsigned int channel, const char *buf, size_t count) { unsigned int flags = STP_PACKET_TIMESTAMPED; const unsigned char *p = buf, nil = 0; @@ -393,9 +437,14 @@ static void stm_write(struct stm_data *data, unsigned int master, sz = data->packet(data, master, channel, STP_PACKET_DATA, flags, sz, p); flags = 0; + + if (sz < 0) + break; } data->packet(data, master, channel, STP_PACKET_FLAG, 0, 0, &nil); + + return pos; } static ssize_t stm_char_write(struct file *file, const char __user *buf, @@ -406,6 +455,9 @@ static ssize_t stm_char_write(struct file *file, const char __user *buf, char *kbuf; int err; + if (count + 1 > PAGE_SIZE) + count = PAGE_SIZE - 1; + /* * if no m/c have been assigned to this writer up to this * point, use "default" policy entry @@ -430,8 +482,8 @@ static ssize_t stm_char_write(struct file *file, const char __user *buf, return -EFAULT; } - stm_write(stm->data, stmf->output.master, stmf->output.channel, kbuf, - count); + count = stm_write(stm->data, stmf->output.master, stmf->output.channel, + kbuf, count); kfree(kbuf); @@ -509,16 +561,12 @@ static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg) if (ret) goto err_free; - ret = 0; - if (stm->data->link) ret = stm->data->link(stm->data, stmf->output.master, stmf->output.channel); - if (ret) { + if (ret) stm_output_free(stmf->stm, &stmf->output); - stm_put_device(stmf->stm); - } err_free: kfree(id); @@ -633,17 +681,11 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data, stm->dev.parent = parent; stm->dev.release = stm_device_release; - err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name); - if (err) - goto err_device; - - err = device_add(&stm->dev); - if (err) - goto err_device; - + mutex_init(&stm->link_mutex); spin_lock_init(&stm->link_lock); INIT_LIST_HEAD(&stm->link_list); + /* initialize the object before it is accessible via sysfs */ spin_lock_init(&stm->mc_lock); mutex_init(&stm->policy_mutex); stm->sw_nmasters = nmasters; @@ -651,9 +693,20 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data, stm->data = stm_data; stm_data->stm = stm; + err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name); + if (err) + goto err_device; + + err = device_add(&stm->dev); + if (err) + goto err_device; + return 0; err_device: + unregister_chrdev(stm->major, stm_data->name); + + /* matches device_initialize() above */ put_device(&stm->dev); err_free: kfree(stm); @@ -662,20 +715,28 @@ err_free: } EXPORT_SYMBOL_GPL(stm_register_device); -static void __stm_source_link_drop(struct stm_source_device *src, - struct stm_device *stm); +static int __stm_source_link_drop(struct stm_source_device *src, + struct stm_device *stm); void stm_unregister_device(struct stm_data *stm_data) { struct stm_device *stm = stm_data->stm; struct stm_source_device *src, *iter; - int i; + int i, ret; - spin_lock(&stm->link_lock); + mutex_lock(&stm->link_mutex); list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) { - __stm_source_link_drop(src, stm); + ret = __stm_source_link_drop(src, stm); + /* + * src <-> stm link must not change under the same + * stm::link_mutex, so complain loudly if it has; + * also in this situation ret!=0 means this src is + * not connected to this stm and it should be otherwise + * safe to proceed with the tear-down of stm. + */ + WARN_ON_ONCE(ret); } - spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); synchronize_srcu(&stm_source_srcu); @@ -694,6 +755,17 @@ void stm_unregister_device(struct stm_data *stm_data) } EXPORT_SYMBOL_GPL(stm_unregister_device); +/* + * stm::link_list access serialization uses a spinlock and a mutex; holding + * either of them guarantees that the list is stable; modification requires + * holding both of them. + * + * Lock ordering is as follows: + * stm::link_mutex + * stm::link_lock + * src::link_lock + */ + /** * stm_source_link_add() - connect an stm_source device to an stm device * @src: stm_source device @@ -710,6 +782,7 @@ static int stm_source_link_add(struct stm_source_device *src, char *id; int err; + mutex_lock(&stm->link_mutex); spin_lock(&stm->link_lock); spin_lock(&src->link_lock); @@ -719,6 +792,7 @@ static int stm_source_link_add(struct stm_source_device *src, spin_unlock(&src->link_lock); spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); id = kstrdup(src->data->name, GFP_KERNEL); if (id) { @@ -753,9 +827,9 @@ static int stm_source_link_add(struct stm_source_device *src, fail_free_output: stm_output_free(stm, &src->output); - stm_put_device(stm); fail_detach: + mutex_lock(&stm->link_mutex); spin_lock(&stm->link_lock); spin_lock(&src->link_lock); @@ -764,6 +838,7 @@ fail_detach: spin_unlock(&src->link_lock); spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); return err; } @@ -776,28 +851,55 @@ fail_detach: * If @stm is @src::link, disconnect them from one another and put the * reference on the @stm device. * - * Caller must hold stm::link_lock. + * Caller must hold stm::link_mutex. */ -static void __stm_source_link_drop(struct stm_source_device *src, - struct stm_device *stm) +static int __stm_source_link_drop(struct stm_source_device *src, + struct stm_device *stm) { struct stm_device *link; + int ret = 0; + + lockdep_assert_held(&stm->link_mutex); + /* for stm::link_list modification, we hold both mutex and spinlock */ + spin_lock(&stm->link_lock); spin_lock(&src->link_lock); link = srcu_dereference_check(src->link, &stm_source_srcu, 1); - if (WARN_ON_ONCE(link != stm)) { - spin_unlock(&src->link_lock); - return; + + /* + * The linked device may have changed since we last looked, because + * we weren't holding the src::link_lock back then; if this is the + * case, tell the caller to retry. + */ + if (link != stm) { + ret = -EAGAIN; + goto unlock; } stm_output_free(link, &src->output); - /* caller must hold stm::link_lock */ list_del_init(&src->link_entry); /* matches stm_find_device() from stm_source_link_store() */ stm_put_device(link); rcu_assign_pointer(src->link, NULL); +unlock: spin_unlock(&src->link_lock); + spin_unlock(&stm->link_lock); + + /* + * Call the unlink callbacks for both source and stm, when we know + * that we have actually performed the unlinking. + */ + if (!ret) { + if (src->data->unlink) + src->data->unlink(src->data); + + if (stm->data->unlink) + stm->data->unlink(stm->data, src->output.master, + src->output.channel); + } + + return ret; } /** @@ -813,21 +915,29 @@ static void __stm_source_link_drop(struct stm_source_device *src, static void stm_source_link_drop(struct stm_source_device *src) { struct stm_device *stm; - int idx; + int idx, ret; +retry: idx = srcu_read_lock(&stm_source_srcu); + /* + * The stm device will be valid for the duration of this + * read section, but the link may change before we grab + * the src::link_lock in __stm_source_link_drop(). + */ stm = srcu_dereference(src->link, &stm_source_srcu); + ret = 0; if (stm) { - if (src->data->unlink) - src->data->unlink(src->data); - - spin_lock(&stm->link_lock); - __stm_source_link_drop(src, stm); - spin_unlock(&stm->link_lock); + mutex_lock(&stm->link_mutex); + ret = __stm_source_link_drop(src, stm); + mutex_unlock(&stm->link_mutex); } srcu_read_unlock(&stm_source_srcu, idx); + + /* if it did change, retry */ + if (ret == -EAGAIN) + goto retry; } static ssize_t stm_source_link_show(struct device *dev, @@ -862,8 +972,10 @@ static ssize_t stm_source_link_store(struct device *dev, return -EINVAL; err = stm_source_link_add(src, link); - if (err) + if (err) { + /* matches the stm_find_device() above */ stm_put_device(link); + } return err ? : count; } @@ -925,6 +1037,7 @@ int stm_source_register_device(struct device *parent, if (err) goto err; + stm_output_init(&src->output); spin_lock_init(&src->link_lock); INIT_LIST_HEAD(&src->link_entry); src->data = data; @@ -973,9 +1086,9 @@ int stm_source_write(struct stm_source_data *data, unsigned int chan, stm = srcu_dereference(src->link, &stm_source_srcu); if (stm) - stm_write(stm->data, src->output.master, - src->output.channel + chan, - buf, count); + count = stm_write(stm->data, src->output.master, + src->output.channel + chan, + buf, count); else count = -ENODEV; diff --git a/drivers/hwtracing/stm/dummy_stm.c b/drivers/hwtracing/stm/dummy_stm.c index 3709bef0b21f..a86612d989f9 100644 --- a/drivers/hwtracing/stm/dummy_stm.c +++ b/drivers/hwtracing/stm/dummy_stm.c @@ -40,22 +40,71 @@ dummy_stm_packet(struct stm_data *stm_data, unsigned int master, return size; } -static struct stm_data dummy_stm = { - .name = "dummy_stm", - .sw_start = 0x0000, - .sw_end = 0xffff, - .sw_nchannels = 0xffff, - .packet = dummy_stm_packet, -}; +#define DUMMY_STM_MAX 32 + +static struct stm_data dummy_stm[DUMMY_STM_MAX]; + +static int nr_dummies = 4; + +module_param(nr_dummies, int, 0400); + +static unsigned int fail_mode; + +module_param(fail_mode, int, 0600); + +static int dummy_stm_link(struct stm_data *data, unsigned int master, + unsigned int channel) +{ + if (fail_mode && (channel & fail_mode)) + return -EINVAL; + + return 0; +} static int dummy_stm_init(void) { - return stm_register_device(NULL, &dummy_stm, THIS_MODULE); + int i, ret = -ENOMEM; + + if (nr_dummies < 0 || nr_dummies > DUMMY_STM_MAX) + return -EINVAL; + + for (i = 0; i < nr_dummies; i++) { + dummy_stm[i].name = kasprintf(GFP_KERNEL, "dummy_stm.%d", i); + if (!dummy_stm[i].name) + goto fail_unregister; + + dummy_stm[i].sw_start = 0x0000; + dummy_stm[i].sw_end = 0xffff; + dummy_stm[i].sw_nchannels = 0xffff; + dummy_stm[i].packet = dummy_stm_packet; + dummy_stm[i].link = dummy_stm_link; + + ret = stm_register_device(NULL, &dummy_stm[i], THIS_MODULE); + if (ret) + goto fail_free; + } + + return 0; + +fail_unregister: + for (i--; i >= 0; i--) { + stm_unregister_device(&dummy_stm[i]); +fail_free: + kfree(dummy_stm[i].name); + } + + return ret; + } static void dummy_stm_exit(void) { - stm_unregister_device(&dummy_stm); + int i; + + for (i = 0; i < nr_dummies; i++) { + stm_unregister_device(&dummy_stm[i]); + kfree(dummy_stm[i].name); + } } module_init(dummy_stm_init); diff --git a/drivers/hwtracing/stm/heartbeat.c b/drivers/hwtracing/stm/heartbeat.c new file mode 100644 index 000000000000..3da7b673aab2 --- /dev/null +++ b/drivers/hwtracing/stm/heartbeat.c @@ -0,0 +1,126 @@ +/* + * Simple heartbeat STM source driver + * Copyright (c) 2016, Intel Corporation. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * This program is distributed in the hope it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * Heartbeat STM source will send repetitive messages over STM devices to a + * trace host. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/hrtimer.h> +#include <linux/slab.h> +#include <linux/stm.h> + +#define STM_HEARTBEAT_MAX 32 + +static int nr_devs = 4; +static int interval_ms = 10; + +module_param(nr_devs, int, 0400); +module_param(interval_ms, int, 0600); + +static struct stm_heartbeat { + struct stm_source_data data; + struct hrtimer hrtimer; + unsigned int active; +} stm_heartbeat[STM_HEARTBEAT_MAX]; + +static const char str[] = "heartbeat stm source driver is here to serve you"; + +static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr) +{ + struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat, + hrtimer); + + stm_source_write(&heartbeat->data, 0, str, sizeof str); + if (heartbeat->active) + hrtimer_forward_now(hr, ms_to_ktime(interval_ms)); + + return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART; +} + +static int stm_heartbeat_link(struct stm_source_data *data) +{ + struct stm_heartbeat *heartbeat = + container_of(data, struct stm_heartbeat, data); + + heartbeat->active = 1; + hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms), + HRTIMER_MODE_ABS); + + return 0; +} + +static void stm_heartbeat_unlink(struct stm_source_data *data) +{ + struct stm_heartbeat *heartbeat = + container_of(data, struct stm_heartbeat, data); + + heartbeat->active = 0; + hrtimer_cancel(&heartbeat->hrtimer); +} + +static int stm_heartbeat_init(void) +{ + int i, ret = -ENOMEM; + + if (nr_devs < 0 || nr_devs > STM_HEARTBEAT_MAX) + return -EINVAL; + + for (i = 0; i < nr_devs; i++) { + stm_heartbeat[i].data.name = + kasprintf(GFP_KERNEL, "heartbeat.%d", i); + if (!stm_heartbeat[i].data.name) + goto fail_unregister; + + stm_heartbeat[i].data.nr_chans = 1; + stm_heartbeat[i].data.link = stm_heartbeat_link; + stm_heartbeat[i].data.unlink = stm_heartbeat_unlink; + hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC, + HRTIMER_MODE_ABS); + stm_heartbeat[i].hrtimer.function = + stm_heartbeat_hrtimer_handler; + + ret = stm_source_register_device(NULL, &stm_heartbeat[i].data); + if (ret) + goto fail_free; + } + + return 0; + +fail_unregister: + for (i--; i >= 0; i--) { + stm_source_unregister_device(&stm_heartbeat[i].data); +fail_free: + kfree(stm_heartbeat[i].data.name); + } + + return ret; +} + +static void stm_heartbeat_exit(void) +{ + int i; + + for (i = 0; i < nr_devs; i++) { + stm_source_unregister_device(&stm_heartbeat[i].data); + kfree(stm_heartbeat[i].data.name); + } +} + +module_init(stm_heartbeat_init); +module_exit(stm_heartbeat_exit); + +MODULE_LICENSE("GPL v2"); +MODULE_DESCRIPTION("stm_heartbeat driver"); +MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>"); diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c index 11ab6d01adf6..1c061cb9bff0 100644 --- a/drivers/hwtracing/stm/policy.c +++ b/drivers/hwtracing/stm/policy.c @@ -272,13 +272,17 @@ void stp_policy_unbind(struct stp_policy *policy) { struct stm_device *stm = policy->stm; + /* + * stp_policy_release() will not call here if the policy is already + * unbound; other users should not either, as no link exists between + * this policy and anything else in that case + */ if (WARN_ON_ONCE(!policy->stm)) return; - mutex_lock(&stm->policy_mutex); - stm->policy = NULL; - mutex_unlock(&stm->policy_mutex); + lockdep_assert_held(&stm->policy_mutex); + stm->policy = NULL; policy->stm = NULL; stm_put_device(stm); @@ -287,8 +291,16 @@ void stp_policy_unbind(struct stp_policy *policy) static void stp_policy_release(struct config_item *item) { struct stp_policy *policy = to_stp_policy(item); + struct stm_device *stm = policy->stm; + /* a policy *can* be unbound and still exist in configfs tree */ + if (!stm) + return; + + mutex_lock(&stm->policy_mutex); stp_policy_unbind(policy); + mutex_unlock(&stm->policy_mutex); + kfree(policy); } @@ -320,16 +332,17 @@ stp_policies_make(struct config_group *group, const char *name) /* * node must look like <device_name>.<policy_name>, where - * <device_name> is the name of an existing stm device and - * <policy_name> is an arbitrary string + * <device_name> is the name of an existing stm device; may + * contain dots; + * <policy_name> is an arbitrary string; may not contain dots */ - p = strchr(devname, '.'); + p = strrchr(devname, '.'); if (!p) { kfree(devname); return ERR_PTR(-EINVAL); } - *p++ = '\0'; + *p = '\0'; stm = stm_find_device(devname); kfree(devname); diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h index 95ece0292c99..4e8c6926260f 100644 --- a/drivers/hwtracing/stm/stm.h +++ b/drivers/hwtracing/stm/stm.h @@ -45,6 +45,7 @@ struct stm_device { int major; unsigned int sw_nmasters; struct stm_data *data; + struct mutex link_mutex; spinlock_t link_lock; struct list_head link_list; /* master allocation */ @@ -56,6 +57,7 @@ struct stm_device { container_of((_d), struct stm_device, dev) struct stm_output { + spinlock_t lock; unsigned int master; unsigned int channel; unsigned int nr_chans; |