[09/10] usb: Add USB subsystem notifications [ver #3]
diff mbox series

Message ID 155981420247.17513.18371208824032389940.stgit@warthog.procyon.org.uk
State New
Headers show
Series
  • Mount, FS, Block and Keyrings notifications [ver #3]
Related show

Commit Message

David Howells June 6, 2019, 9:43 a.m. UTC
Add a USB subsystem notification mechanism whereby notifications about
hardware events such as device connection, disconnection, reset and I/O
errors, can be reported to a monitoring process asynchronously.

Firstly, an event queue needs to be created:

	fd = open("/dev/event_queue", O_RDWR);
	ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, page_size << n);

then a notification can be set up to report USB notifications via that
queue:

	struct watch_notification_filter filter = {
		.nr_filters = 1,
		.filters = {
			[0] = {
				.type = WATCH_TYPE_USB_NOTIFY,
				.subtype_filter[0] = UINT_MAX;
			},
		},
	};
	ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter);
	device_notify(fd, 12);

After that, records will be placed into the queue when events occur on a
USB device or bus.  Records are of the following format:

	struct usb_notification {
		struct watch_notification watch;
		__u32	error;
		__u32	reserved;
		__u8	name_len;
		__u8	name[0];
	} *n;

Where:

	n->watch.type will be WATCH_TYPE_USB_NOTIFY

	n->watch.subtype will be the type of notification, such as
	NOTIFY_USB_DEVICE_ADD.

	n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
	record.

	n->watch.info & WATCH_INFO_ID will be the second argument to
	device_notify(), shifted.

	n->error and n->reserved are intended to convey information such as
	error codes, but are currently not used

	n->name_len and n->name convey the USB device name as an
	unterminated string.  This may be truncated - it is currently
	limited to a maximum 63 chars.

Note that it is permissible for event records to be of variable length -
or, at least, the length may be dependent on the subtype.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cc: linux-usb@vger.kernel.org
---

 Documentation/watch_queue.rst    |    9 ++++++
 drivers/usb/core/Kconfig         |   10 +++++++
 drivers/usb/core/devio.c         |   55 ++++++++++++++++++++++++++++++++++++++
 drivers/usb/core/hub.c           |    3 ++
 include/linux/usb.h              |   19 +++++++++++++
 include/uapi/linux/watch_queue.h |   30 ++++++++++++++++++++-
 6 files changed, 125 insertions(+), 1 deletion(-)

Comments

Alan Stern June 6, 2019, 2:24 p.m. UTC | #1
On Thu, 6 Jun 2019, David Howells wrote:

> Add a USB subsystem notification mechanism whereby notifications about
> hardware events such as device connection, disconnection, reset and I/O
> errors, can be reported to a monitoring process asynchronously.

USB I/O errors covers an awfully large and vague field.  Do we really
want to include them?  I'm doubtful.

Alan Stern
Greg Kroah-Hartman June 6, 2019, 2:33 p.m. UTC | #2
On Thu, Jun 06, 2019 at 10:24:18AM -0400, Alan Stern wrote:
> On Thu, 6 Jun 2019, David Howells wrote:
> 
> > Add a USB subsystem notification mechanism whereby notifications about
> > hardware events such as device connection, disconnection, reset and I/O
> > errors, can be reported to a monitoring process asynchronously.
> 
> USB I/O errors covers an awfully large and vague field.  Do we really
> want to include them?  I'm doubtful.

See the other patch on the linux-usb list that wanted to start adding
KOBJ_CHANGE notifications about USB "i/o errors".

So for "severe" issues, yes, we should do this, but perhaps not for all
of the "normal" things we see when a device is yanked out of the system
and the like.

thanks,

greg k-h
Alan Stern June 6, 2019, 2:55 p.m. UTC | #3
On Thu, 6 Jun 2019, Greg Kroah-Hartman wrote:

> On Thu, Jun 06, 2019 at 10:24:18AM -0400, Alan Stern wrote:
> > On Thu, 6 Jun 2019, David Howells wrote:
> > 
> > > Add a USB subsystem notification mechanism whereby notifications about
> > > hardware events such as device connection, disconnection, reset and I/O
> > > errors, can be reported to a monitoring process asynchronously.
> > 
> > USB I/O errors covers an awfully large and vague field.  Do we really
> > want to include them?  I'm doubtful.
> 
> See the other patch on the linux-usb list that wanted to start adding
> KOBJ_CHANGE notifications about USB "i/o errors".

That patch wanted to add notifications only for enumeration failures
(assuming you're talking about the patch from Eugeniu Rosca), not I/O
errors in general.

> So for "severe" issues, yes, we should do this, but perhaps not for all
> of the "normal" things we see when a device is yanked out of the system
> and the like.

Then what counts as a "severe" issue?  Anything besides enumeration 
failure?

Alan Stern
Greg Kroah-Hartman June 6, 2019, 3:31 p.m. UTC | #4
On Thu, Jun 06, 2019 at 10:55:24AM -0400, Alan Stern wrote:
> On Thu, 6 Jun 2019, Greg Kroah-Hartman wrote:
> 
> > On Thu, Jun 06, 2019 at 10:24:18AM -0400, Alan Stern wrote:
> > > On Thu, 6 Jun 2019, David Howells wrote:
> > > 
> > > > Add a USB subsystem notification mechanism whereby notifications about
> > > > hardware events such as device connection, disconnection, reset and I/O
> > > > errors, can be reported to a monitoring process asynchronously.
> > > 
> > > USB I/O errors covers an awfully large and vague field.  Do we really
> > > want to include them?  I'm doubtful.
> > 
> > See the other patch on the linux-usb list that wanted to start adding
> > KOBJ_CHANGE notifications about USB "i/o errors".
> 
> That patch wanted to add notifications only for enumeration failures
> (assuming you're talking about the patch from Eugeniu Rosca), not I/O
> errors in general.

Yes, sorry, I was thinking that as a "I/O failed in enumeration" :)

> > So for "severe" issues, yes, we should do this, but perhaps not for all
> > of the "normal" things we see when a device is yanked out of the system
> > and the like.
> 
> Then what counts as a "severe" issue?  Anything besides enumeration 
> failure?

Not that I can think of at the moment, other than the other recently
added KOBJ_CHANGE issue.  I'm sure we have other "hard failure" issues
in the USB stack that people will want exposed over time.

thanks,

greg k-h
Felipe Balbi June 7, 2019, 6:40 a.m. UTC | #5
Hi,

Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
> On Thu, Jun 06, 2019 at 10:55:24AM -0400, Alan Stern wrote:
>> On Thu, 6 Jun 2019, Greg Kroah-Hartman wrote:
>> 
>> > On Thu, Jun 06, 2019 at 10:24:18AM -0400, Alan Stern wrote:
>> > > On Thu, 6 Jun 2019, David Howells wrote:
>> > > 
>> > > > Add a USB subsystem notification mechanism whereby notifications about
>> > > > hardware events such as device connection, disconnection, reset and I/O
>> > > > errors, can be reported to a monitoring process asynchronously.
>> > > 
>> > > USB I/O errors covers an awfully large and vague field.  Do we really
>> > > want to include them?  I'm doubtful.
>> > 
>> > See the other patch on the linux-usb list that wanted to start adding
>> > KOBJ_CHANGE notifications about USB "i/o errors".
>> 
>> That patch wanted to add notifications only for enumeration failures
>> (assuming you're talking about the patch from Eugeniu Rosca), not I/O
>> errors in general.
>
> Yes, sorry, I was thinking that as a "I/O failed in enumeration" :)
>
>> > So for "severe" issues, yes, we should do this, but perhaps not for all
>> > of the "normal" things we see when a device is yanked out of the system
>> > and the like.
>> 
>> Then what counts as a "severe" issue?  Anything besides enumeration 
>> failure?
>
> Not that I can think of at the moment, other than the other recently
> added KOBJ_CHANGE issue.  I'm sure we have other "hard failure" issues
> in the USB stack that people will want exposed over time.

From an XHCI standpoint, Transaction Errors might be one thing. They
happen rarely and are a strong indication that the bus itself is
bad. Either bad cable, misbehaving PHYs, improper power management, etc.
Alan Stern June 7, 2019, 2:01 p.m. UTC | #6
On Fri, 7 Jun 2019, Felipe Balbi wrote:

> Hi,
> 
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
> > On Thu, Jun 06, 2019 at 10:55:24AM -0400, Alan Stern wrote:
> >> On Thu, 6 Jun 2019, Greg Kroah-Hartman wrote:
> >> 
> >> > On Thu, Jun 06, 2019 at 10:24:18AM -0400, Alan Stern wrote:
> >> > > On Thu, 6 Jun 2019, David Howells wrote:
> >> > > 
> >> > > > Add a USB subsystem notification mechanism whereby notifications about
> >> > > > hardware events such as device connection, disconnection, reset and I/O
> >> > > > errors, can be reported to a monitoring process asynchronously.
> >> > > 
> >> > > USB I/O errors covers an awfully large and vague field.  Do we really
> >> > > want to include them?  I'm doubtful.
> >> > 
> >> > See the other patch on the linux-usb list that wanted to start adding
> >> > KOBJ_CHANGE notifications about USB "i/o errors".
> >> 
> >> That patch wanted to add notifications only for enumeration failures
> >> (assuming you're talking about the patch from Eugeniu Rosca), not I/O
> >> errors in general.
> >
> > Yes, sorry, I was thinking that as a "I/O failed in enumeration" :)
> >
> >> > So for "severe" issues, yes, we should do this, but perhaps not for all
> >> > of the "normal" things we see when a device is yanked out of the system
> >> > and the like.
> >> 
> >> Then what counts as a "severe" issue?  Anything besides enumeration 
> >> failure?
> >
> > Not that I can think of at the moment, other than the other recently
> > added KOBJ_CHANGE issue.  I'm sure we have other "hard failure" issues
> > in the USB stack that people will want exposed over time.
> 
> From an XHCI standpoint, Transaction Errors might be one thing. They
> happen rarely and are a strong indication that the bus itself is
> bad. Either bad cable, misbehaving PHYs, improper power management, etc.

Don't you also get transaction errors if the user unplugs a device in 
the middle of a transfer?  That's not the sort of thing we want to sent 
notifications about.

Alan Stern
Felipe Balbi June 11, 2019, 6:28 a.m. UTC | #7
Hi,

Alan Stern <stern@rowland.harvard.edu> writes:
>> Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
>> > On Thu, Jun 06, 2019 at 10:55:24AM -0400, Alan Stern wrote:
>> >> On Thu, 6 Jun 2019, Greg Kroah-Hartman wrote:
>> >> 
>> >> > On Thu, Jun 06, 2019 at 10:24:18AM -0400, Alan Stern wrote:
>> >> > > On Thu, 6 Jun 2019, David Howells wrote:
>> >> > > 
>> >> > > > Add a USB subsystem notification mechanism whereby notifications about
>> >> > > > hardware events such as device connection, disconnection, reset and I/O
>> >> > > > errors, can be reported to a monitoring process asynchronously.
>> >> > > 
>> >> > > USB I/O errors covers an awfully large and vague field.  Do we really
>> >> > > want to include them?  I'm doubtful.
>> >> > 
>> >> > See the other patch on the linux-usb list that wanted to start adding
>> >> > KOBJ_CHANGE notifications about USB "i/o errors".
>> >> 
>> >> That patch wanted to add notifications only for enumeration failures
>> >> (assuming you're talking about the patch from Eugeniu Rosca), not I/O
>> >> errors in general.
>> >
>> > Yes, sorry, I was thinking that as a "I/O failed in enumeration" :)
>> >
>> >> > So for "severe" issues, yes, we should do this, but perhaps not for all
>> >> > of the "normal" things we see when a device is yanked out of the system
>> >> > and the like.
>> >> 
>> >> Then what counts as a "severe" issue?  Anything besides enumeration 
>> >> failure?
>> >
>> > Not that I can think of at the moment, other than the other recently
>> > added KOBJ_CHANGE issue.  I'm sure we have other "hard failure" issues
>> > in the USB stack that people will want exposed over time.
>> 
>> From an XHCI standpoint, Transaction Errors might be one thing. They
>> happen rarely and are a strong indication that the bus itself is
>> bad. Either bad cable, misbehaving PHYs, improper power management, etc.
>
> Don't you also get transaction errors if the user unplugs a device in 
> the middle of a transfer?  That's not the sort of thing we want to sent 
> notifications about.

Mathias, do we get Transaction Error if user removes cable during a
transfer? I thought we would just get Port Status Change with CC bit
cleared, no?
Alan Stern June 11, 2019, 1:53 p.m. UTC | #8
On Tue, 11 Jun 2019, Felipe Balbi wrote:

> >> >> > So for "severe" issues, yes, we should do this, but perhaps not for all
> >> >> > of the "normal" things we see when a device is yanked out of the system
> >> >> > and the like.
> >> >> 
> >> >> Then what counts as a "severe" issue?  Anything besides enumeration 
> >> >> failure?
> >> >
> >> > Not that I can think of at the moment, other than the other recently
> >> > added KOBJ_CHANGE issue.  I'm sure we have other "hard failure" issues
> >> > in the USB stack that people will want exposed over time.
> >> 
> >> From an XHCI standpoint, Transaction Errors might be one thing. They
> >> happen rarely and are a strong indication that the bus itself is
> >> bad. Either bad cable, misbehaving PHYs, improper power management, etc.
> >
> > Don't you also get transaction errors if the user unplugs a device in 
> > the middle of a transfer?  That's not the sort of thing we want to sent 
> > notifications about.
> 
> Mathias, do we get Transaction Error if user removes cable during a
> transfer? I thought we would just get Port Status Change with CC bit
> cleared, no?

Even if xHCI doesn't give Transaction Errors when a cable is unplugged 
during a transfer, other host controllers do.  Sometimes quite a lot -- 
they continue to occur until the kernel polls the parent hub's 
interrupt ep and learns that the port is disconnected, which can take 
up to 250 ms.

Alan Stern
Felipe Balbi June 12, 2019, 6:58 a.m. UTC | #9
Hi,

Alan Stern <stern@rowland.harvard.edu> writes:

> On Tue, 11 Jun 2019, Felipe Balbi wrote:
>
>> >> >> > So for "severe" issues, yes, we should do this, but perhaps not for all
>> >> >> > of the "normal" things we see when a device is yanked out of the system
>> >> >> > and the like.
>> >> >> 
>> >> >> Then what counts as a "severe" issue?  Anything besides enumeration 
>> >> >> failure?
>> >> >
>> >> > Not that I can think of at the moment, other than the other recently
>> >> > added KOBJ_CHANGE issue.  I'm sure we have other "hard failure" issues
>> >> > in the USB stack that people will want exposed over time.
>> >> 
>> >> From an XHCI standpoint, Transaction Errors might be one thing. They
>> >> happen rarely and are a strong indication that the bus itself is
>> >> bad. Either bad cable, misbehaving PHYs, improper power management, etc.
>> >
>> > Don't you also get transaction errors if the user unplugs a device in 
>> > the middle of a transfer?  That's not the sort of thing we want to sent 
>> > notifications about.
>> 
>> Mathias, do we get Transaction Error if user removes cable during a
>> transfer? I thought we would just get Port Status Change with CC bit
>> cleared, no?
>
> Even if xHCI doesn't give Transaction Errors when a cable is unplugged 
> during a transfer, other host controllers do.  Sometimes quite a lot -- 
> they continue to occur until the kernel polls the parent hub's 
> interrupt ep and learns that the port is disconnected, which can take 
> up to 250 ms.

my comment was specific about XHCI. It even started with "From an XHCI
standpoint" :-)

Patch
diff mbox series

diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
index c2954e191989..7ce5d4147fa9 100644
--- a/Documentation/watch_queue.rst
+++ b/Documentation/watch_queue.rst
@@ -15,6 +15,8 @@  receive notifications from the kernel.  This can be used in conjunction with::
 
     * Block layer event notifications
 
+    * USB subsystem event notifications
+
 
 The notifications buffers can be enabled by:
 
@@ -344,6 +346,13 @@  Any particular buffer can be fed from multiple sources.  Sources include:
     or temporary link loss.  Watchpoints of this type are set on the global
     device watch list.
 
+  * WATCH_TYPE_USB_NOTIFY
+
+    Notifications of this type indicate USB subsystem events, such as
+    attachment, removal, reset and I/O errors.  Separate events are generated
+    for buses and devices.  Watchpoints of this type are set on the global
+    device watch list.
+
 
 Event Filtering
 ===============
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index bdb6bd0b63a6..4be88368ab6b 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -103,3 +103,13 @@  config USB_AUTOSUSPEND_DELAY
 	  The default value Linux has always had is 2 seconds.  Change
 	  this value if you want a different delay and cannot modify
 	  the command line or module parameter.
+
+config USB_NOTIFICATIONS
+	bool "Provide USB hardware event notifications"
+	depends on USB
+	select DEVICE_NOTIFICATIONS
+	help
+	  This option provides support for getting hardware event notifications
+	  on USB devices and interfaces.  This makes use of the
+	  /dev/watch_queue misc device to handle the notification buffer.
+	  device_notify(2) is used to set/remove watches.
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index fa783531ee88..af7f339c35c5 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -41,6 +41,7 @@ 
 #include <linux/dma-mapping.h>
 #include <asm/byteorder.h>
 #include <linux/moduleparam.h>
+#include <linux/watch_queue.h>
 
 #include "usb.h"
 
@@ -2633,13 +2634,67 @@  static void usbdev_remove(struct usb_device *udev)
 	}
 }
 
+#ifdef CONFIG_USB_NOTIFICATIONS
+static noinline void post_usb_notification(const char *devname,
+					   enum usb_notification_type subtype,
+					   u32 error)
+{
+	unsigned int name_len, n_len;
+	u64 id = 0; /* Might want to put a dev# here. */
+
+	struct {
+		struct usb_notification n;
+		char more_name[USB_NOTIFICATION_MAX_NAME_LEN -
+			       (sizeof(struct usb_notification) -
+				offsetof(struct usb_notification, name))];
+	} n;
+
+	name_len = strlen(devname);
+	name_len = min_t(size_t, name_len, USB_NOTIFICATION_MAX_NAME_LEN);
+	n_len = round_up(offsetof(struct usb_notification, name) + name_len,
+			 sizeof(__u64));
+
+	memset(&n, 0, sizeof(n));
+	memcpy(n.n.name, devname, n_len);
+
+	n.n.watch.type		= WATCH_TYPE_USB_NOTIFY;
+	n.n.watch.subtype	= subtype;
+	n.n.watch.info		= n_len;
+	n.n.error		= error;
+	n.n.name_len		= name_len;
+
+	post_device_notification(&n.n.watch, id);
+}
+
+void post_usb_device_notification(const struct usb_device *udev,
+				  enum usb_notification_type subtype, u32 error)
+{
+	post_usb_notification(dev_name(&udev->dev), subtype, error);
+}
+
+void post_usb_bus_notification(const struct usb_bus *ubus,
+			       enum usb_notification_type subtype, u32 error)
+{
+	post_usb_notification(ubus->bus_name, subtype, error);
+}
+#endif
+
 static int usbdev_notify(struct notifier_block *self,
 			       unsigned long action, void *dev)
 {
 	switch (action) {
 	case USB_DEVICE_ADD:
+		post_usb_device_notification(dev, NOTIFY_USB_DEVICE_ADD, 0);
 		break;
 	case USB_DEVICE_REMOVE:
+		post_usb_device_notification(dev, NOTIFY_USB_DEVICE_REMOVE, 0);
+		usbdev_remove(dev);
+		break;
+	case USB_BUS_ADD:
+		post_usb_bus_notification(dev, NOTIFY_USB_BUS_ADD, 0);
+		break;
+	case USB_BUS_REMOVE:
+		post_usb_bus_notification(dev, NOTIFY_USB_BUS_REMOVE, 0);
 		usbdev_remove(dev);
 		break;
 	}
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 2f94568ba385..722013d8142c 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -4596,6 +4596,9 @@  hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 				(udev->config) ? "reset" : "new", speed,
 				devnum, driver_name);
 
+	if (udev->config)
+		post_usb_device_notification(udev, NOTIFY_USB_DEVICE_RESET, 0);
+
 	/* Set up TT records, if needed  */
 	if (hdev->tt) {
 		udev->tt = hdev->tt;
diff --git a/include/linux/usb.h b/include/linux/usb.h
index ae82d9d1112b..12687b55811d 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -2008,6 +2008,25 @@  extern void usb_led_activity(enum usb_led_event ev);
 static inline void usb_led_activity(enum usb_led_event ev) {}
 #endif
 
+/*
+ * Notification functions.
+ */
+#ifdef CONFIG_USB_NOTIFICATIONS
+extern void post_usb_device_notification(const struct usb_device *udev,
+					 enum usb_notification_type subtype,
+					 u32 error);
+extern void post_usb_bus_notification(const struct usb_bus *ubus,
+				      enum usb_notification_type subtype,
+				      u32 error);
+#else
+static inline void post_usb_device_notification(const struct usb_device *udev,
+						enum usb_notification_type subtype,
+						u32 error) {}
+static inline void post_usb_bus_notification(const struct usb_bus *ubus,
+					     enum usb_notification_type subtype,
+					     u32 error) {}
+#endif
+
 #endif  /* __KERNEL__ */
 
 #endif
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 22e3326b83a6..d596ac5a61e4 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -14,7 +14,8 @@  enum watch_notification_type {
 	WATCH_TYPE_SB_NOTIFY	= 2,	/* Superblock notification */
 	WATCH_TYPE_KEY_NOTIFY	= 3,	/* Key/keyring change notification */
 	WATCH_TYPE_BLOCK_NOTIFY	= 4,	/* Block layer notifications */
-#define WATCH_TYPE___NR 5
+	WATCH_TYPE_USB_NOTIFY	= 5,	/* USB subsystem notifications */
+#define WATCH_TYPE___NR 6
 };
 
 enum watch_meta_notification_subtype {
@@ -182,4 +183,31 @@  struct block_notification {
 	__u64	sector;			/* Affected sector */
 };
 
+/*
+ * Type of USB layer notification.
+ */
+enum usb_notification_type {
+	NOTIFY_USB_DEVICE_ADD		= 0, /* USB device added */
+	NOTIFY_USB_DEVICE_REMOVE	= 1, /* USB device removed */
+	NOTIFY_USB_BUS_ADD		= 2, /* USB bus added */
+	NOTIFY_USB_BUS_REMOVE		= 3, /* USB bus removed */
+	NOTIFY_USB_DEVICE_RESET		= 4, /* USB device reset */
+	NOTIFY_USB_DEVICE_ERROR		= 5, /* USB device error */
+};
+
+/*
+ * USB subsystem notification record.
+ * - watch.type = WATCH_TYPE_USB_NOTIFY
+ * - watch.subtype = enum usb_notification_type
+ */
+struct usb_notification {
+	struct watch_notification watch; /* WATCH_TYPE_USB_NOTIFY */
+	__u32	error;
+	__u32	reserved;
+	__u8	name_len;		/* Length of device name */
+	__u8	name[0];		/* Device name (padded to __u64, truncated at 63 chars) */
+};
+
+#define USB_NOTIFICATION_MAX_NAME_LEN 63
+
 #endif /* _UAPI_LINUX_WATCH_QUEUE_H */