After commit 1cbd53c8cd85 ("usb: core: introduce per-port over-current
counters") usb ports expose a sysfs value 'over_current_count'
to user space. This value on its own is not very useful as it requires
manual polling.
As a solution, fire a udev event from the usb hub device that specifies
the values 'OVER_CURRENT_PORT' and 'OVER_CURRENT_COUNT' that indicate
the path of the usb port where the over-current event occurred and the
value of 'over_current_count' in sysfs. Additionally, call
sysfs_notify() so the sysfs value supports poll().
Signed-off-by: Jon Flatley <jflat@xxxxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-bus-usb | 9 ++++++-
drivers/usb/core/hub.c | 36 +++++++++++++++++++++++++
2 files changed, 44 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index 08d456e07b53..c4a70f532ec3 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -219,7 +219,14 @@ Description:
ports and report them to the kernel. This attribute is to expose
the number of over-current situation occurred on a specific port
to user space. This file will contain an unsigned 32 bit value
- which wraps to 0 after its maximum is reached.
+ which wraps to 0 after its maximum is reached. This file supports
+ poll() for monitoring changes to this value in user space.
+
+ Any time this value changes the corresponding hub device will send a
+ udev event with the following attributes:
+
+ OVER_CURRENT_PORT=/sys/bus/usb/devices/.../(hub interface)/portX
+ OVER_CURRENT_COUNT=[current value of this sysfs attribute]
What: /sys/bus/usb/devices/.../(hub interface)/portX/usb3_lpm_permit
Date: November 2015
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 462ce49f683a..7801bb30bdba 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -28,6 +28,7 @@
#include <linux/mutex.h>
#include <linux/random.h>
#include <linux/pm_qos.h>
+#include <linux/kobject.h>
#include <linux/uaccess.h>
#include <asm/byteorder.h>
@@ -5147,6 +5148,40 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
usb_lock_port(port_dev);
}
+/* Handle notifying userspace about hub over-current events */
+static void port_over_current_notify(struct usb_port *port_dev)
+{
+ static char *envp[] = { NULL, NULL, NULL };
+ struct device *hub_dev;
+ char *port_dev_path;
+
+ sysfs_notify(&port_dev->dev.kobj, NULL, "over_current_count");
+
+ hub_dev = port_dev->dev.parent;
+
+ if (!hub_dev)
+ return;
+
+ port_dev_path = kobject_get_path(&port_dev->dev.kobj, GFP_KERNEL);
+ if (!port_dev_path)
+ return;
+
+ envp[0] = kasprintf(GFP_KERNEL, "OVER_CURRENT_PORT=%s", port_dev_path);
+ if (!envp[0])
+ return;
+
+ envp[1] = kasprintf(GFP_KERNEL, "OVER_CURRENT_COUNT=%u",
+ port_dev->over_current_count);
+ if (!envp[1])
+ goto exit;
+
+ kobject_uevent_env(&hub_dev->kobj, KOBJ_CHANGE, envp);
+
+ kfree(envp[1]);
+exit:
+ kfree(envp[0]);
+}
+
static void port_event(struct usb_hub *hub, int port1)
__must_hold(&port_dev->status_lock)
{
@@ -5189,6 +5224,7 @@ static void port_event(struct usb_hub *hub, int port1)
if (portchange & USB_PORT_STAT_C_OVERCURRENT) {
u16 status = 0, unused;
port_dev->over_current_count++;
+ port_over_current_notify(port_dev);
dev_dbg(&port_dev->dev, "over-current change #%u\n",
port_dev->over_current_count);
--
2.19.0.444.g18242da7ef-goog
