It's helpful to be able to look at device link details from sysfs. So,
expose it in sysfs.
Say device-A is supplier of device-B. These are the additional files
this patch would create:
/sys/class/devlink/device-A:device-B/
flags
supplier/ -> .../device-A/
consumer/ -> .../device-B/
/sys/devices/.../device-A/
consumer:device-B/ -> /sys/class/devlink/device-A:device-B/
/sys/devices/.../device-B/
supplier:device-A/ -> /sys/class/devlink/device-A:device-B/
That way:
To get a list of all the device link in the system:
ls /sys/class/devlink/
To get the consumer names and links of a device:
ls -d /sys/devices/.../device-X/consumer:*
To get the supplier names and links of a device:
ls -d /sys/devices/.../device-X/supplier:*
For now, I'm just exporting "flags", supplier and consumer for each
device link. But the goal is to expand it to "state", etc once the
overall idea is accepted.
Signed-off-by: Saravana Kannan <sarava...@google.com>
---
Greg/Rafael,
Wanted to check if both of you are okay with the overall idea of
exporting device link details through sysfs and if using a "struct
device" is how you'd like to do it. I think this information would be
helpful in debugging all kinds of suspend/resume, probe and power issues
in a production system. I didn't want to spend more time on this patch
before I got your okays.
I'm not too familiar with the right way to do kobjs and symlinks in
sysfs -- so apologies any crazy code. But overall, the patch does create
the layout I describe above and seems to work.
I could also remove kref and switch to using link_dev to keep track of
refcount and releasing stuff, but I wasn't sure if we really needed the
srcu implementation or not. So didn't remove it in this series and left
it as is.
Known issues:
- There seem to be some issue in the srcu clean up path where it can't
find the "consumer" and "supplier" links to remove. I need to debug
that. It could be one due to one of those weird dwc3 drivers. Just a
FYI in case you spot something wrong with my patch. Pointers welcome.
"kernfs : can not remove 'consumer', no directory"
Thanks,
Saravana
drivers/base/core.c | 129 ++++++++++++++++++++++++++++++++++++++++-
include/linux/device.h | 58 +++++++++---------
2 files changed, 156 insertions(+), 31 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 0b7aff8f0412..3f05c910b244 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -52,6 +52,7 @@ static unsigned int defer_sync_state_count = 1;
static unsigned int defer_fw_devlink_count;
static DEFINE_MUTEX(defer_fw_devlink_lock);
static bool fw_devlink_is_permissive(void);
+static void __device_link_del(struct kref *kref);
#ifdef CONFIG_SRCU
static DEFINE_MUTEX(device_links_lock);
@@ -235,6 +236,108 @@ void device_pm_move_to_tail(struct device *dev)
device_links_read_unlock(idx);
}
+#define to_devlink(dev) container_of((dev), struct device_link,
link_dev)
+
+static ssize_t flags_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%08x\n", to_devlink(dev)->flags);
+}
+static DEVICE_ATTR_RO(flags);
+
+static struct attribute *devlink_attrs[] = {
+ &dev_attr_flags.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(devlink);
+
+static struct class devlink_class = {
+ .name = "devlink",
+ .owner = THIS_MODULE,
+ .dev_groups = devlink_groups,
+};
+
+static int __init devlink_class_init(void)
+{
+ return class_register(&devlink_class);
+}
+postcore_initcall(devlink_class_init);
+
+static int devlink_add_symlinks(struct device_link *link)
+{
+ int ret;
+ size_t len;
+ struct device *sup = link->supplier;
+ struct device *con = link->consumer;
+ char *buf;
+
+ len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
+ len += strlen("supplier:") + 1;
+ buf = kzalloc(len, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ ret = sysfs_create_link(&link->link_dev.kobj, &sup->kobj, "supplier");
+ if (ret)
+ goto out;
+
+ ret = sysfs_create_link(&link->link_dev.kobj, &con->kobj, "consumer");
+ if (ret)
+ goto err_con;
+
+ snprintf(buf, len, "consumer:%s", dev_name(con));
+ ret = sysfs_create_link(&sup->kobj, &link->link_dev.kobj, buf);
+ if (ret)
+ goto err_con_dev;
+
+ snprintf(buf, len, "supplier:%s", dev_name(sup));
+ ret = sysfs_create_link(&con->kobj, &link->link_dev.kobj, buf);
+ if (ret)
+ goto err_sup_dev;
+
+ goto out;
+
+err_sup_dev:
+ snprintf(buf, len, "consumer:%s", dev_name(con));
+ sysfs_remove_link(&sup->kobj, buf);
+err_con_dev:
+ sysfs_remove_link(&link->link_dev.kobj, "consumer");
+err_con:
+ sysfs_remove_link(&link->link_dev.kobj, "supplier");
+out:
+ kfree(buf);
+ return ret;
+}
+
+static void device_link_dev_release(struct device *dev)
+{
+ struct device_link *link = to_devlink(dev);
+ size_t len;
+ struct device *sup = link->supplier;
+ struct device *con = link->consumer;
+ char *buf;
+
+ sysfs_remove_link(&link->link_dev.kobj, "consumer");
+ sysfs_remove_link(&link->link_dev.kobj, "supplier");
+
+ len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
+ len += strlen("supplier:") + 1;
+ buf = kzalloc(len, GFP_KERNEL);
+ if (!buf) {
+ WARN(1, "Unable to properly free device link!\n");
+ return;
+ }
+
+ snprintf(buf, len, "supplier:%s", dev_name(sup));
+ sysfs_remove_link(&con->kobj, buf);
+ snprintf(buf, len, "consumer:%s", dev_name(con));
+ sysfs_remove_link(&sup->kobj, buf);
+ kfree(buf);
+ put_device(link->consumer);
+ put_device(link->supplier);
+ kfree(link);
+}
+
#define DL_MANAGED_LINK_FLAGS (DL_FLAG_AUTOREMOVE_CONSUMER | \
DL_FLAG_AUTOREMOVE_SUPPLIER | \
DL_FLAG_AUTOPROBE_CONSUMER | \
@@ -422,6 +525,17 @@ struct device_link *device_link_add(struct device
*consumer,
link->flags = flags;
kref_init(&link->kref);
+ link->link_dev.class = &devlink_class;
+ link->link_dev.release = &device_link_dev_release;
+ device_set_pm_not_required(&link->link_dev);
+ dev_set_name(&link->link_dev, "%s:%s",
+ dev_name(supplier), dev_name(consumer));
+
+ if (device_register(&link->link_dev))
+ goto err_dev_reg;
+ if (devlink_add_symlinks(link))
+ goto err_symlinks;
+
/* Determine the initial link state. */
if (flags & DL_FLAG_STATELESS)
link->status = DL_STATE_NONE;
@@ -466,6 +580,14 @@ struct device_link *device_link_add(struct device
*consumer,
pm_runtime_put(supplier);
return link;
+
+err_symlinks:
+ device_unregister(&link->link_dev);
+err_dev_reg:
+ kref_put(&link->kref, __device_link_del);
+ device_pm_unlock();
+ device_links_write_unlock();
+ return NULL;
}
EXPORT_SYMBOL_GPL(device_link_add);
@@ -542,9 +664,7 @@ static void device_link_free(struct device_link *link)
while (refcount_dec_not_one(&link->rpm_active))
pm_runtime_put(link->supplier);
- put_device(link->consumer);
- put_device(link->supplier);
- kfree(link);
+ device_unregister(&link->link_dev);
}
#ifdef CONFIG_SRCU
@@ -1123,6 +1243,9 @@ static void device_links_purge(struct device *dev)
{
struct device_link *link, *ln;
+ if (dev->class == &devlink_class)
+ return;
+
mutex_lock(&wfs_lock);
list_del(&dev->links.needs_suppliers);
mutex_unlock(&wfs_lock);
diff --git a/include/linux/device.h b/include/linux/device.h
index ac8e37cd716a..4c10afed9cd6 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -386,34 +386,6 @@ enum device_link_state {
#define DL_FLAG_MANAGED BIT(6)
#define DL_FLAG_SYNC_STATE_ONLY BIT(7)
-/**
- * struct device_link - Device link representation.
- * @supplier: The device on the supplier end of the link.
- * @s_node: Hook to the supplier device's list of links to consumers.
- * @consumer: The device on the consumer end of the link.
- * @c_node: Hook to the consumer device's list of links to suppliers.
- * @status: The state of the link (with respect to the presence of drivers).
- * @flags: Link flags.
- * @rpm_active: Whether or not the consumer device is runtime-PM-active.
- * @kref: Count repeated addition of the same link.
- * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks.
- * @supplier_preactivated: Supplier has been made active before consumer probe.
- */
-struct device_link {
- struct device *supplier;
- struct list_head s_node;
- struct device *consumer;
- struct list_head c_node;
- enum device_link_state status;
- u32 flags;
- refcount_t rpm_active;
- struct kref kref;
-#ifdef CONFIG_SRCU
- struct rcu_head rcu_head;
-#endif
- bool supplier_preactivated; /* Owned by consumer probe. */
-};
-
/**
* enum dl_dev_state - Device driver presence tracking information.
* @DL_DEV_NO_DRIVER: There is no driver attached to the device.
@@ -624,6 +596,36 @@ struct device {
#endif
};
+/**
+ * struct device_link - Device link representation.
+ * @supplier: The device on the supplier end of the link.
+ * @s_node: Hook to the supplier device's list of links to consumers.
+ * @consumer: The device on the consumer end of the link.
+ * @c_node: Hook to the consumer device's list of links to suppliers.
+ * @link_dev: device used to expose link details in sysfs
+ * @status: The state of the link (with respect to the presence of drivers).
+ * @flags: Link flags.
+ * @rpm_active: Whether or not the consumer device is runtime-PM-active.
+ * @kref: Count repeated addition of the same link.
+ * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks.
+ * @supplier_preactivated: Supplier has been made active before consumer probe.
+ */
+struct device_link {
+ struct device *supplier;
+ struct list_head s_node;
+ struct device *consumer;
+ struct list_head c_node;
+ struct device link_dev;
+ enum device_link_state status;
+ u32 flags;
+ refcount_t rpm_active;
+ struct kref kref;
+#ifdef CONFIG_SRCU
+ struct rcu_head rcu_head;
+#endif
+ bool supplier_preactivated; /* Owned by consumer probe. */
+};
+
static inline struct device *kobj_to_dev(struct kobject *kobj)
{
return container_of(kobj, struct device, kobj);
--
2.26.2.761.g0e0b3e54be-goog
