blob: 2712e699ba08cf2d30415eef43287b36cdc5ec75 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* System Trace Module (STM) infrastructure
* Copyright (c) 2014, Intel Corporation.
*
* STM class implements generic infrastructure for System Trace Module devices
* as defined in MIPI STPv2 specification.
*/
#include <linux/pm_runtime.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/compat.h>
#include <linux/kdev_t.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/stm.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include "stm.h"
#include <uapi/linux/stm.h>
static unsigned int stm_core_up;
/*
* The SRCU here makes sure that STM device doesn't disappear from under a
* stm_source_write() caller, which may want to have as little overhead as
* possible.
*/
static struct srcu_struct stm_source_srcu;
static ssize_t masters_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct stm_device *stm = to_stm_device(dev);
int ret;
ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end);
return ret;
}
static DEVICE_ATTR_RO(masters);
static ssize_t channels_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->sw_nchannels);
return ret;
}
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,
};
ATTRIBUTE_GROUPS(stm);
static struct class stm_class = {
.name = "stm",
.dev_groups = stm_groups,
};
/**
* stm_find_device() - find stm device by name
* @buf: character buffer containing the name
*
* This is called when either policy gets assigned to an stm device or an
* stm_source device gets linked to an stm device.
*
* This grabs device's reference (get_device()) and module reference, both
* of which the calling path needs to make sure to drop with stm_put_device().
*
* Return: stm device pointer or null if lookup failed.
*/
struct stm_device *stm_find_device(const char *buf)
{
struct stm_device *stm;
struct device *dev;
if (!stm_core_up)
return NULL;
dev = class_find_device_by_name(&stm_class, buf);
if (!dev)
return NULL;
stm = to_stm_device(dev);
if (!try_module_get(stm->owner)) {
/* matches class_find_device() above */
put_device(dev);
return NULL;
}
return stm;
}
/**
* stm_put_device() - drop references on the stm device
* @stm: stm device, previously acquired by stm_find_device()
*
* This drops the module reference and device reference taken by
* stm_find_device() or stm_char_open().
*/
void stm_put_device(struct stm_device *stm)
{
module_put(stm->owner);
put_device(&stm->dev);
}
/*
* Internally we only care about software-writable masters here, that is the
* ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
* original master numbers to be visible externally, since they are the ones
* that will appear in the STP stream. Thus, the internal bookkeeping uses
* $master - stm_data->sw_start to reference master descriptors and such.
*/
#define __stm_master(_s, _m) \
((_s)->masters[(_m) - (_s)->data->sw_start])
static inline struct stp_master *
stm_master(struct stm_device *stm, unsigned int idx)
{
if (idx < stm->data->sw_start || idx > stm->data->sw_end)
return NULL;
return __stm_master(stm, idx);
}
static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
{
struct stp_master *master;
master = kzalloc(struct_size(master, chan_map,
BITS_TO_LONGS(stm->data->sw_nchannels)),
GFP_ATOMIC);
if (!master)
return -ENOMEM;
master->nr_free = stm->data->sw_nchannels;
__stm_master(stm, idx) = master;
return 0;
}
static void stp_master_free(struct stm_device *stm, unsigned int idx)
{
struct stp_master *master = stm_master(stm, idx);
if (!master)
return;
__stm_master(stm, idx) = NULL;
kfree(master);
}
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;
bitmap_allocate_region(&master->chan_map[0], output->channel,
ilog2(output->nr_chans));
master->nr_free -= output->nr_chans;
}
static void
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));
master->nr_free += output->nr_chans;
output->nr_chans = 0;
}
/*
* This is like bitmap_find_free_region(), except it can ignore @start bits
* at the beginning.
*/
static int find_free_channels(unsigned long *bitmap, unsigned int start,
unsigned int end, unsigned int width)
{
unsigned int pos;
int i;
for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
pos = find_next_zero_bit(bitmap, end + 1, pos);
if (pos + width > end + 1)
break;
if (pos & (width - 1))
continue;
for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
;
if (i == width)
return pos;
/* step over [pos..pos+i) to continue search */
pos += i;
}
return -1;
}
static int
stm_find_master_chan(struct stm_device *stm, unsigned int width,
unsigned int *mstart, unsigned int mend,
unsigned int *cstart, unsigned int cend)
{
struct stp_master *master;
unsigned int midx;
int pos, err;
for (midx = *mstart; midx <= mend; midx++) {
if (!stm_master(stm, midx)) {
err = stp_master_alloc(stm, midx);
if (err)
return err;
}
master = stm_master(stm, midx);
if (!master->nr_free)
continue;
pos = find_free_channels(master->chan_map, *cstart, cend,
width);
if (pos < 0)
continue;
*mstart = midx;
*cstart = pos;
return 0;
}
return -ENOSPC;
}
static int stm_output_assign(struct stm_device *stm, unsigned int width,
struct stp_policy_node *policy_node,
struct stm_output *output)
{
unsigned int midx, cidx, mend, cend;
int ret = -EINVAL;
if (width > stm->data->sw_nchannels)
return -EINVAL;
/* We no longer accept policy_node==NULL here */
if (WARN_ON_ONCE(!policy_node))
return -EINVAL;
/*
* Also, the caller holds reference to policy_node, so it won't
* disappear on us.
*/
stp_policy_node_get_ranges(policy_node, &midx, &mend, &cidx, &cend);
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;
ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
if (ret < 0)
goto unlock;
output->master = midx;
output->channel = cidx;
output->nr_chans = width;
if (stm->pdrv->output_open) {
void *priv = stp_policy_node_priv(policy_node);
if (WARN_ON_ONCE(!priv))
goto unlock;
/* configfs subsys mutex is held by the caller */
ret = stm->pdrv->output_open(priv, output);
if (ret)
goto unlock;
}
stm_output_claim(stm, output);
dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);
ret = 0;
unlock:
if (ret)
output->nr_chans = 0;
spin_unlock(&output->lock);
spin_unlock(&stm->mc_lock);
return ret;
}
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);
if (stm->pdrv && stm->pdrv->output_close)
stm->pdrv->output_close(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;
return MAJOR(dev->devt) == major;
}
/*
* Framing protocol management
* Modules can implement STM protocol drivers and (un-)register them
* with the STM class framework.
*/
static struct list_head stm_pdrv_head;
static struct mutex stm_pdrv_mutex;
struct stm_pdrv_entry {
struct list_head entry;
const struct stm_protocol_driver *pdrv;
const struct config_item_type *node_type;
};
static const struct stm_pdrv_entry *
__stm_lookup_protocol(const char *name)
{
struct stm_pdrv_entry *pe;
/*
* If no name is given (NULL or ""), fall back to "p_basic".
*/
if (!name || !*name)
name = "p_basic";
list_for_each_entry(pe, &stm_pdrv_head, entry) {
if (!strcmp(name, pe->pdrv->name))
return pe;
}
return NULL;
}
int stm_register_protocol(const struct stm_protocol_driver *pdrv)
{
struct stm_pdrv_entry *pe = NULL;
int ret = -ENOMEM;
mutex_lock(&stm_pdrv_mutex);
if (__stm_lookup_protocol(pdrv->name)) {
ret = -EEXIST;
goto unlock;
}
pe = kzalloc(sizeof(*pe), GFP_KERNEL);
if (!pe)
goto unlock;
if (pdrv->policy_attr) {
pe->node_type = get_policy_node_type(pdrv->policy_attr);
if (!pe->node_type)
goto unlock;
}
list_add_tail(&pe->entry, &stm_pdrv_head);
pe->pdrv = pdrv;
ret = 0;
unlock:
mutex_unlock(&stm_pdrv_mutex);
if (ret)
kfree(pe);
return ret;
}
EXPORT_SYMBOL_GPL(stm_register_protocol);
void stm_unregister_protocol(const struct stm_protocol_driver *pdrv)
{
struct stm_pdrv_entry *pe, *iter;
mutex_lock(&stm_pdrv_mutex);
list_for_each_entry_safe(pe, iter, &stm_pdrv_head, entry) {
if (pe->pdrv == pdrv) {
list_del(&pe->entry);
if (pe->node_type) {
kfree(pe->node_type->ct_attrs);
kfree(pe->node_type);
}
kfree(pe);
break;
}
}
mutex_unlock(&stm_pdrv_mutex);
}
EXPORT_SYMBOL_GPL(stm_unregister_protocol);
static bool stm_get_protocol(const struct stm_protocol_driver *pdrv)
{
return try_module_get(pdrv->owner);
}
void stm_put_protocol(const struct stm_protocol_driver *pdrv)
{
module_put(pdrv->owner);
}
int stm_lookup_protocol(const char *name,
const struct stm_protocol_driver **pdrv,
const struct config_item_type **node_type)
{
const struct stm_pdrv_entry *pe;
mutex_lock(&stm_pdrv_mutex);
pe = __stm_lookup_protocol(name);
if (pe && pe->pdrv && stm_get_protocol(pe->pdrv)) {
*pdrv = pe->pdrv;
*node_type = pe->node_type;
}
mutex_unlock(&stm_pdrv_mutex);
return pe ? 0 : -ENOENT;
}
static int stm_char_open(struct inode *inode, struct file *file)
{
struct stm_file *stmf;
struct device *dev;
unsigned int major = imajor(inode);
int err = -ENOMEM;
dev = class_find_device(&stm_class, NULL, &major, major_match);
if (!dev)
return -ENODEV;
stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
if (!stmf)
goto err_put_device;
err = -ENODEV;
stm_output_init(&stmf->output);
stmf->stm = to_stm_device(dev);
if (!try_module_get(stmf->stm->owner))
goto err_free;
file->private_data = stmf;
return nonseekable_open(inode, file);
err_free:
kfree(stmf);
err_put_device:
/* matches class_find_device() above */
put_device(dev);
return err;
}
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);
/*
* matches the stm_char_open()'s
* class_find_device() + try_module_get()
*/
stm_put_device(stm);
kfree(stmf);
return 0;
}
static int
stm_assign_first_policy(struct stm_device *stm, struct stm_output *output,
char **ids, unsigned int width)
{
struct stp_policy_node *pn;
int err, n;
/*
* On success, stp_policy_node_lookup() will return holding the
* configfs subsystem mutex, which is then released in
* stp_policy_node_put(). This allows the pdrv->output_open() in
* stm_output_assign() to serialize against the attribute accessors.
*/
for (n = 0, pn = NULL; ids[n] && !pn; n++)
pn = stp_policy_node_lookup(stm, ids[n]);
if (!pn)
return -EINVAL;
err = stm_output_assign(stm, width, pn, output);
stp_policy_node_put(pn);
return err;
}
/**
* stm_data_write() - send the given payload as data packets
* @data: stm driver's data
* @m: STP master
* @c: STP channel
* @ts_first: timestamp the first packet
* @buf: data payload buffer
* @count: data payload size
*/
ssize_t notrace stm_data_write(struct stm_data *data, unsigned int m,
unsigned int c, bool ts_first, const void *buf,
size_t count)
{
unsigned int flags = ts_first ? STP_PACKET_TIMESTAMPED : 0;
ssize_t sz;
size_t pos;
for (pos = 0, sz = 0; pos < count; pos += sz) {
sz = min_t(unsigned int, count - pos, 8);
sz = data->packet(data, m, c, STP_PACKET_DATA, flags, sz,
&((u8 *)buf)[pos]);
if (sz <= 0)
break;
if (ts_first) {
flags = 0;
ts_first = false;
}
}
return sz < 0 ? sz : pos;
}
EXPORT_SYMBOL_GPL(stm_data_write);
static ssize_t notrace
stm_write(struct stm_device *stm, struct stm_output *output,
unsigned int chan, const char *buf, size_t count)
{
int err;
/* stm->pdrv is serialized against policy_mutex */
if (!stm->pdrv)
return -ENODEV;
err = stm->pdrv->write(stm->data, output, chan, buf, count);
if (err < 0)
return err;
return err;
}
static ssize_t stm_char_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct stm_file *stmf = file->private_data;
struct stm_device *stm = stmf->stm;
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, try to use the task name and "default" policy entries.
*/
if (!stmf->output.nr_chans) {
char comm[sizeof(current->comm)];
char *ids[] = { comm, "default", NULL };
get_task_comm(comm, current);
err = stm_assign_first_policy(stmf->stm, &stmf->output, ids, 1);
/*
* EBUSY means that somebody else just assigned this
* output, which is just fine for write()
*/
if (err)
return err;
}
kbuf = kmalloc(count + 1, GFP_KERNEL);
if (!kbuf)
return -ENOMEM;
err = copy_from_user(kbuf, buf, count);
if (err) {
kfree(kbuf);
return -EFAULT;
}
pm_runtime_get_sync(&stm->dev);
count = stm_write(stm, &stmf->output, 0, kbuf, count);
pm_runtime_mark_last_busy(&stm->dev);
pm_runtime_put_autosuspend(&stm->dev);
kfree(kbuf);
return count;
}
static void stm_mmap_open(struct vm_area_struct *vma)
{
struct stm_file *stmf = vma->vm_file->private_data;
struct stm_device *stm = stmf->stm;
pm_runtime_get(&stm->dev);
}
static void stm_mmap_close(struct vm_area_struct *vma)
{
struct stm_file *stmf = vma->vm_file->private_data;
struct stm_device *stm = stmf->stm;
pm_runtime_mark_last_busy(&stm->dev);
pm_runtime_put_autosuspend(&stm->dev);
}
static const struct vm_operations_struct stm_mmap_vmops = {
.open = stm_mmap_open,
.close = stm_mmap_close,
};
static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
{
struct stm_file *stmf = file->private_data;
struct stm_device *stm = stmf->stm;
unsigned long size, phys;
if (!stm->data->mmio_addr)
return -EOPNOTSUPP;
if (vma->vm_pgoff)
return -EINVAL;
size = vma->vm_end - vma->vm_start;
if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
return -EINVAL;
phys = stm->data->mmio_addr(stm->data, stmf->output.master,
stmf->output.channel,
stmf->output.nr_chans);
if (!phys)
return -EINVAL;
pm_runtime_get_sync(&stm->dev);
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
vma->vm_ops = &stm_mmap_vmops;
vm_iomap_memory(vma, phys, size);
return 0;
}
static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
{
struct stm_device *stm = stmf->stm;
struct stp_policy_id *id;
char *ids[] = { NULL, NULL };
int ret = -EINVAL, wlimit = 1;
u32 size;
if (stmf->output.nr_chans)
return -EBUSY;
if (copy_from_user(&size, arg, sizeof(size)))
return -EFAULT;
if (size < sizeof(*id) || size >= PATH_MAX + sizeof(*id))
return -EINVAL;
/*
* size + 1 to make sure the .id string at the bottom is terminated,
* which is also why memdup_user() is not useful here
*/
id = kzalloc(size + 1, GFP_KERNEL);
if (!id)
return -ENOMEM;
if (copy_from_user(id, arg, size)) {
ret = -EFAULT;
goto err_free;
}
if (id->__reserved_0 || id->__reserved_1)
goto err_free;
if (stm->data->sw_mmiosz)
wlimit = PAGE_SIZE / stm->data->sw_mmiosz;
if (id->width < 1 || id->width > wlimit)
goto err_free;
ids[0] = id->id;
ret = stm_assign_first_policy(stmf->stm, &stmf->output, ids,
id->width);
if (ret)
goto err_free;
if (stm->data->link)
ret = stm->data->link(stm->data, stmf->output.master,
stmf->output.channel);
if (ret)
stm_output_free(stmf->stm, &stmf->output);
err_free:
kfree(id);
return ret;
}
static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
{
struct stp_policy_id id = {
.size = sizeof(id),
.master = stmf->output.master,
.channel = stmf->output.channel,
.width = stmf->output.nr_chans,
.__reserved_0 = 0,
.__reserved_1 = 0,
};
return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
}
static long
stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct stm_file *stmf = file->private_data;
struct stm_data *stm_data = stmf->stm->data;
int err = -ENOTTY;
u64 options;
switch (cmd) {
case STP_POLICY_ID_SET:
err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
if (err)
return err;
return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
case STP_POLICY_ID_GET:
return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
case STP_SET_OPTIONS:
if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
return -EFAULT;
if (stm_data->set_options)
err = stm_data->set_options(stm_data,
stmf->output.master,
stmf->output.channel,
stmf->output.nr_chans,
options);
break;
default:
break;
}
return err;
}
static const struct file_operations stm_fops = {
.open = stm_char_open,
.release = stm_char_release,
.write = stm_char_write,
.mmap = stm_char_mmap,
.unlocked_ioctl = stm_char_ioctl,
.compat_ioctl = compat_ptr_ioctl,
.llseek = no_llseek,
};
static void stm_device_release(struct device *dev)
{
struct stm_device *stm = to_stm_device(dev);
vfree(stm);
}
int stm_register_device(struct device *parent, struct stm_data *stm_data,
struct module *owner)
{
struct stm_device *stm;
unsigned int nmasters;
int err = -ENOMEM;
if (!stm_core_up)
return -EPROBE_DEFER;
if (!stm_data->packet || !stm_data->sw_nchannels)
return -EINVAL;
nmasters = stm_data->sw_end - stm_data->sw_start + 1;
stm = vzalloc(sizeof(*stm) + nmasters * sizeof(void *));
if (!stm)
return -ENOMEM;
stm->major = register_chrdev(0, stm_data->name, &stm_fops);
if (stm->major < 0)
goto err_free;
device_initialize(&stm->dev);
stm->dev.devt = MKDEV(stm->major, 0);
stm->dev.class = &stm_class;
stm->dev.parent = parent;
stm->dev.release = stm_device_release;
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;
stm->owner = owner;
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;
/*
* Use delayed autosuspend to avoid bouncing back and forth
* on recurring character device writes, with the initial
* delay time of 2 seconds.
*/
pm_runtime_no_callbacks(&stm->dev);
pm_runtime_use_autosuspend(&stm->dev);
pm_runtime_set_autosuspend_delay(&stm->dev, 2000);
pm_runtime_set_suspended(&stm->dev);
pm_runtime_enable(&stm->dev);
return 0;
err_device:
unregister_chrdev(stm->major, stm_data->name);
/* matches device_initialize() above */
put_device(&stm->dev);
err_free:
vfree(stm);
return err;
}
EXPORT_SYMBOL_GPL(stm_register_device);
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, ret;
pm_runtime_dont_use_autosuspend(&stm->dev);
pm_runtime_disable(&stm->dev);
mutex_lock(&stm->link_mutex);
list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
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);
}
mutex_unlock(&stm->link_mutex);
synchronize_srcu(&stm_source_srcu);
unregister_chrdev(stm->major, stm_data->name);
mutex_lock(&stm->policy_mutex);
if (stm->policy)
stp_policy_unbind(stm->policy);
mutex_unlock(&stm->policy_mutex);
for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
stp_master_free(stm, i);
device_unregister(&stm->dev);
stm_data->stm = NULL;
}
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
* @stm: stm device
*
* This function establishes a link from stm_source to an stm device so that
* the former can send out trace data to the latter.
*
* Return: 0 on success, -errno otherwise.
*/
static int stm_source_link_add(struct stm_source_device *src,
struct stm_device *stm)
{
char *ids[] = { NULL, "default", NULL };
int err = -ENOMEM;
mutex_lock(&stm->link_mutex);
spin_lock(&stm->link_lock);
spin_lock(&src->link_lock);
/* src->link is dereferenced under stm_source_srcu but not the list */
rcu_assign_pointer(src->link, stm);
list_add_tail(&src->link_entry, &stm->link_list);
spin_unlock(&src->link_lock);
spin_unlock(&stm->link_lock);
mutex_unlock(&stm->link_mutex);
ids[0] = kstrdup(src->data->name, GFP_KERNEL);
if (!ids[0])
goto fail_detach;
err = stm_assign_first_policy(stm, &src->output, ids,
src->data->nr_chans);
kfree(ids[0]);
if (err)
goto fail_detach;
/* this is to notify the STM device that a new link has been made */
if (stm->data->link)
err = stm->data->link(stm->data, src->output.master,
src->output.channel);
if (err)
goto fail_free_output;
/* this is to let the source carry out all necessary preparations */
if (src->data->link)
src->data->link(src->data);
return 0;
fail_free_output:
stm_output_free(stm, &src->output);
fail_detach:
mutex_lock(&stm->link_mutex);
spin_lock(&stm->link_lock);
spin_lock(&src->link_lock);
rcu_assign_pointer(src->link, NULL);
list_del_init(&src->link_entry);
spin_unlock(&src->link_lock);
spin_unlock(&stm->link_lock);
mutex_unlock(&stm->link_mutex);
return err;
}
/**
* __stm_source_link_drop() - detach stm_source from an stm device
* @src: stm_source device
* @stm: stm device
*
* If @stm is @src::link, disconnect them from one another and put the
* reference on the @stm device.
*
* Caller must hold stm::link_mutex.
*/
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);
/*
* 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);
list_del_init(&src->link_entry);
pm_runtime_mark_last_busy(&link->dev);
pm_runtime_put_autosuspend(&link->dev);
/* 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;
}
/**
* stm_source_link_drop() - detach stm_source from its stm device
* @src: stm_source device
*
* Unlinking means disconnecting from source's STM device; after this
* writes will be unsuccessful until it is linked to a new STM device.
*
* This will happen on "stm_source_link" sysfs attribute write to undo
* the existing link (if any), or on linked STM device's de-registration.
*/
static void stm_source_link_drop(struct stm_source_device *src)
{
struct stm_device *stm;
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) {
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,
struct device_attribute *attr,
char *buf)
{
struct stm_source_device *src = to_stm_source_device(dev);
struct stm_device *stm;
int idx, ret;
idx = srcu_read_lock(&stm_source_srcu);
stm = srcu_dereference(src->link, &stm_source_srcu);
ret = sprintf(buf, "%s\n",
stm ? dev_name(&stm->dev) : "<none>");
srcu_read_unlock(&stm_source_srcu, idx);
return ret;
}
static ssize_t stm_source_link_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct stm_source_device *src = to_stm_source_device(dev);
struct stm_device *link;
int err;
stm_source_link_drop(src);
link = stm_find_device(buf);
if (!link)
return -EINVAL;
pm_runtime_get(&link->dev);
err = stm_source_link_add(src, link);
if (err) {
pm_runtime_put_autosuspend(&link->dev);
/* matches the stm_find_device() above */
stm_put_device(link);
}
return err ? : count;
}
static DEVICE_ATTR_RW(stm_source_link);
static struct attribute *stm_source_attrs[] = {
&dev_attr_stm_source_link.attr,
NULL,
};
ATTRIBUTE_GROUPS(stm_source);
static struct class stm_source_class = {
.name = "stm_source",
.dev_groups = stm_source_groups,
};
static void stm_source_device_release(struct device *dev)
{
struct stm_source_device *src = to_stm_source_device(dev);
kfree(src);
}
/**
* stm_source_register_device() - register an stm_source device
* @parent: parent device
* @data: device description structure
*
* This will create a device of stm_source class that can write
* data to an stm device once linked.
*
* Return: 0 on success, -errno otherwise.
*/
int stm_source_register_device(struct device *parent,
struct stm_source_data *data)
{
struct stm_source_device *src;
int err;
if (!stm_core_up)
return -EPROBE_DEFER;
src = kzalloc(sizeof(*src), GFP_KERNEL);
if (!src)
return -ENOMEM;
device_initialize(&src->dev);
src->dev.class = &stm_source_class;
src->dev.parent = parent;
src->dev.release = stm_source_device_release;
err = kobject_set_name(&src->dev.kobj, "%s", data->name);
if (err)
goto err;
pm_runtime_no_callbacks(&src->dev);
pm_runtime_forbid(&src->dev);
err = device_add(&src->dev);
if (err)
goto err;
stm_output_init(&src->output);
spin_lock_init(&src->link_lock);
INIT_LIST_HEAD(&src->link_entry);
src->data = data;
data->src = src;
return 0;
err:
put_device(&src->dev);
return err;
}
EXPORT_SYMBOL_GPL(stm_source_register_device);
/**
* stm_source_unregister_device() - unregister an stm_source device
* @data: device description that was used to register the device
*
* This will remove a previously created stm_source device from the system.
*/
void stm_source_unregister_device(struct stm_source_data *data)
{
struct stm_source_device *src = data->src;
stm_source_link_drop(src);
device_unregister(&src->dev);
}
EXPORT_SYMBOL_GPL(stm_source_unregister_device);
int notrace stm_source_write(struct stm_source_data *data,
unsigned int chan,
const char *buf, size_t count)
{
struct stm_source_device *src = data->src;
struct stm_device *stm;
int idx;
if (!src->output.nr_chans)
return -ENODEV;
if (chan >= src->output.nr_chans)
return -EINVAL;
idx = srcu_read_lock(&stm_source_srcu);
stm = srcu_dereference(src->link, &stm_source_srcu);
if (stm)
count = stm_write(stm, &src->output, chan, buf, count);
else
count = -ENODEV;
srcu_read_unlock(&stm_source_srcu, idx);
return count;
}
EXPORT_SYMBOL_GPL(stm_source_write);
static int __init stm_core_init(void)
{
int err;
err = class_register(&stm_class);
if (err)
return err;
err = class_register(&stm_source_class);
if (err)
goto err_stm;
err = stp_configfs_init();
if (err)
goto err_src;
init_srcu_struct(&stm_source_srcu);
INIT_LIST_HEAD(&stm_pdrv_head);
mutex_init(&stm_pdrv_mutex);
/*
* So as to not confuse existing users with a requirement
* to load yet another module, do it here.
*/
if (IS_ENABLED(CONFIG_STM_PROTO_BASIC))
(void)request_module_nowait("stm_p_basic");
stm_core_up++;
return 0;
err_src:
class_unregister(&stm_source_class);
err_stm:
class_unregister(&stm_class);
return err;
}
module_init(stm_core_init);
static void __exit stm_core_exit(void)
{
cleanup_srcu_struct(&stm_source_srcu);
class_unregister(&stm_source_class);
class_unregister(&stm_class);
stp_configfs_exit();
}
module_exit(stm_core_exit);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("System Trace Module device class");
MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");