* [PATCH 01/10] platform/surface: aggregator: Allow devices to be marked as hot-removed
2022-05-20 18:34 [PATCH 00/10] platform/surface: aggregator: Add support for client hot-removal Maximilian Luz
@ 2022-05-20 18:34 ` Maximilian Luz
2022-05-20 18:34 ` [PATCH 02/10] platform/surface: aggregator: Allow notifiers to avoid communication on unregistering Maximilian Luz
2022-05-20 18:34 ` [PATCH 06/10] HID: surface-hid: Add support for hot-removal Maximilian Luz
2 siblings, 0 replies; 5+ messages in thread
From: Maximilian Luz @ 2022-05-20 18:34 UTC (permalink / raw)
To: Hans de Goede
Cc: Maximilian Luz, Mark Gross, Sebastian Reichel, Jiri Kosina,
Benjamin Tissoires, platform-driver-x86, linux-pm, linux-input,
linux-kernel
Some SSAM devices, notably the keyboard cover (keyboard and touchpad) on
the Surface Pro 8, can be hot-removed. When this occurs, communication
with the device may fail and time out. This timeout can unnecessarily
block and slow down device removal and even cause issues when the
devices are detached and re-attached quickly. Thus, communication should
generally be avoided once hot-removal is detected.
While we already remove a device as soon as we detect its (hot-)removal,
the corresponding device driver may still attempt to communicate with
the device during teardown. This is especially critical as communication
failure may also extend to disabling of events, which is typically done
at that stage.
Add a flag to allow marking devices as hot-removed. This can then be
used during client driver teardown to check if any communication
attempts should be avoided.
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
---
include/linux/surface_aggregator/device.h | 48 +++++++++++++++++++++--
1 file changed, 45 insertions(+), 3 deletions(-)
diff --git a/include/linux/surface_aggregator/device.h b/include/linux/surface_aggregator/device.h
index cc257097eb05..491aa7e9f4bc 100644
--- a/include/linux/surface_aggregator/device.h
+++ b/include/linux/surface_aggregator/device.h
@@ -148,17 +148,30 @@ struct ssam_device_uid {
#define SSAM_SDEV(cat, tid, iid, fun) \
SSAM_DEVICE(SSAM_DOMAIN_SERIALHUB, SSAM_SSH_TC_##cat, tid, iid, fun)
+/*
+ * enum ssam_device_flags - Flags for SSAM client devices.
+ * @SSAM_DEVICE_HOT_REMOVED_BIT:
+ * The device has been hot-removed. Further communication with it may time
+ * out and should be avoided.
+ */
+enum ssam_device_flags {
+ SSAM_DEVICE_HOT_REMOVED_BIT = 0,
+};
+
/**
* struct ssam_device - SSAM client device.
- * @dev: Driver model representation of the device.
- * @ctrl: SSAM controller managing this device.
- * @uid: UID identifying the device.
+ * @dev: Driver model representation of the device.
+ * @ctrl: SSAM controller managing this device.
+ * @uid: UID identifying the device.
+ * @flags: Device state flags, see &enum ssam_device_flags.
*/
struct ssam_device {
struct device dev;
struct ssam_controller *ctrl;
struct ssam_device_uid uid;
+
+ unsigned long flags;
};
/**
@@ -240,6 +253,35 @@ struct ssam_device *ssam_device_alloc(struct ssam_controller *ctrl,
int ssam_device_add(struct ssam_device *sdev);
void ssam_device_remove(struct ssam_device *sdev);
+/**
+ * ssam_device_mark_hot_removed() - Mark the given device as hot-removed.
+ * @sdev: The device to mark as hot-removed.
+ *
+ * Mark the device as having been hot-removed. This signals drivers using the
+ * device that communication with the device should be avoided and may lead to
+ * timeouts.
+ */
+static inline void ssam_device_mark_hot_removed(struct ssam_device *sdev)
+{
+ dev_dbg(&sdev->dev, "marking device as hot-removed\n");
+ set_bit(SSAM_DEVICE_HOT_REMOVED_BIT, &sdev->flags);
+}
+
+/**
+ * ssam_device_is_hot_removed() - Check if the given device has been
+ * hot-removed.
+ * @sdev: The device to check.
+ *
+ * Checks if the given device has been marked as hot-removed. See
+ * ssam_device_mark_hot_removed() for more details.
+ *
+ * Return: Returns ``true`` if the device has been marked as hot-removed.
+ */
+static inline bool ssam_device_is_hot_removed(struct ssam_device *sdev)
+{
+ return test_bit(SSAM_DEVICE_HOT_REMOVED_BIT, &sdev->flags);
+}
+
/**
* ssam_device_get() - Increment reference count of SSAM client device.
* @sdev: The device to increment the reference count of.
--
2.36.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 02/10] platform/surface: aggregator: Allow notifiers to avoid communication on unregistering
2022-05-20 18:34 [PATCH 00/10] platform/surface: aggregator: Add support for client hot-removal Maximilian Luz
2022-05-20 18:34 ` [PATCH 01/10] platform/surface: aggregator: Allow devices to be marked as hot-removed Maximilian Luz
@ 2022-05-20 18:34 ` Maximilian Luz
2022-05-20 18:34 ` [PATCH 06/10] HID: surface-hid: Add support for hot-removal Maximilian Luz
2 siblings, 0 replies; 5+ messages in thread
From: Maximilian Luz @ 2022-05-20 18:34 UTC (permalink / raw)
To: Hans de Goede
Cc: Maximilian Luz, Mark Gross, Sebastian Reichel, Jiri Kosina,
Benjamin Tissoires, Jonathan Corbet, platform-driver-x86,
linux-pm, linux-input, linux-doc, linux-kernel
When SSAM client devices have been (physically) hot-removed,
communication attempts with those devices may fail and time out. This
can even extend to event notifiers, due to which timeouts may occur
during device removal, slowing down that process.
Add a parameter to the notifier unregister function that allows skipping
communication with the EC to prevent this. Furthermore, add wrappers for
registering and unregistering notifiers belonging to SSAM client devices
that automatically check if the device has been marked as hot-removed
and communication should be avoided.
Note that non-SSAM client devices can generally not be hot-removed, so
also add a convenience wrapper for those, defaulting to allow
communication.
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
---
.../driver-api/surface_aggregator/client.rst | 6 +-
.../platform/surface/aggregator/controller.c | 53 ++++++++++-----
include/linux/surface_aggregator/controller.h | 24 ++++++-
include/linux/surface_aggregator/device.h | 66 +++++++++++++++++++
4 files changed, 128 insertions(+), 21 deletions(-)
diff --git a/Documentation/driver-api/surface_aggregator/client.rst b/Documentation/driver-api/surface_aggregator/client.rst
index e519d374c378..27f95abdbe99 100644
--- a/Documentation/driver-api/surface_aggregator/client.rst
+++ b/Documentation/driver-api/surface_aggregator/client.rst
@@ -17,6 +17,8 @@
.. |SSAM_DEVICE| replace:: :c:func:`SSAM_DEVICE`
.. |ssam_notifier_register| replace:: :c:func:`ssam_notifier_register`
.. |ssam_notifier_unregister| replace:: :c:func:`ssam_notifier_unregister`
+.. |ssam_device_notifier_register| replace:: :c:func:`ssam_device_notifier_register`
+.. |ssam_device_notifier_unregister| replace:: :c:func:`ssam_device_notifier_unregister`
.. |ssam_request_sync| replace:: :c:func:`ssam_request_sync`
.. |ssam_event_mask| replace:: :c:type:`enum ssam_event_mask <ssam_event_mask>`
@@ -312,7 +314,9 @@ Handling Events
To receive events from the SAM EC, an event notifier must be registered for
the desired event via |ssam_notifier_register|. The notifier must be
unregistered via |ssam_notifier_unregister| once it is not required any
-more.
+more. For |ssam_device| type clients, the |ssam_device_notifier_register| and
+|ssam_device_notifier_unregister| wrappers should be preferred as they properly
+handle hot-removal of client devices.
Event notifiers are registered by providing (at minimum) a callback to call
in case an event has been received, the registry specifying how the event
diff --git a/drivers/platform/surface/aggregator/controller.c b/drivers/platform/surface/aggregator/controller.c
index b8c377b3f932..6de834b52b63 100644
--- a/drivers/platform/surface/aggregator/controller.c
+++ b/drivers/platform/surface/aggregator/controller.c
@@ -2199,16 +2199,26 @@ static int ssam_nf_refcount_enable(struct ssam_controller *ctrl,
}
/**
- * ssam_nf_refcount_disable_free() - Disable event for reference count entry if it is
- * no longer in use and free the corresponding entry.
+ * ssam_nf_refcount_disable_free() - Disable event for reference count entry if
+ * it is no longer in use and free the corresponding entry.
* @ctrl: The controller to disable the event on.
* @entry: The reference count entry for the event to be disabled.
* @flags: The flags used for enabling the event on the EC.
+ * @ec: Flag specifying if the event should actually be disabled on the EC.
*
- * If the reference count equals zero, i.e. the event is no longer requested by
- * any client, the event will be disabled and the corresponding reference count
- * entry freed. The reference count entry must not be used any more after a
- * call to this function.
+ * If ``ec`` equals ``true`` and the reference count equals zero (i.e. the
+ * event is no longer requested by any client), the specified event will be
+ * disabled on the EC via the corresponding request.
+ *
+ * If ``ec`` equals ``false``, no request will be sent to the EC and the event
+ * can be considered in a detached state (i.e. no longer used but still
+ * enabled). Disabling an event via this method may be required for
+ * hot-removable devices, where event disable requests may time out after the
+ * device has been physically removed.
+ *
+ * In both cases, if the reference count equals zero, the corresponding
+ * reference count entry will be freed. The reference count entry must not be
+ * used any more after a call to this function.
*
* Also checks if the flags used for disabling the event match the flags used
* for enabling the event and warns if they do not (regardless of reference
@@ -2223,7 +2233,7 @@ static int ssam_nf_refcount_enable(struct ssam_controller *ctrl,
* returns the status of the event-enable EC command.
*/
static int ssam_nf_refcount_disable_free(struct ssam_controller *ctrl,
- struct ssam_nf_refcount_entry *entry, u8 flags)
+ struct ssam_nf_refcount_entry *entry, u8 flags, bool ec)
{
const struct ssam_event_registry reg = entry->key.reg;
const struct ssam_event_id id = entry->key.id;
@@ -2232,8 +2242,9 @@ static int ssam_nf_refcount_disable_free(struct ssam_controller *ctrl,
lockdep_assert_held(&nf->lock);
- ssam_dbg(ctrl, "disabling event (reg: %#04x, tc: %#04x, iid: %#04x, rc: %d)\n",
- reg.target_category, id.target_category, id.instance, entry->refcount);
+ ssam_dbg(ctrl, "%s event (reg: %#04x, tc: %#04x, iid: %#04x, rc: %d)\n",
+ ec ? "disabling" : "detaching", reg.target_category, id.target_category,
+ id.instance, entry->refcount);
if (entry->flags != flags) {
ssam_warn(ctrl,
@@ -2242,7 +2253,7 @@ static int ssam_nf_refcount_disable_free(struct ssam_controller *ctrl,
id.instance);
}
- if (entry->refcount == 0) {
+ if (ec && entry->refcount == 0) {
status = ssam_ssh_event_disable(ctrl, reg, id, flags);
kfree(entry);
}
@@ -2322,20 +2333,26 @@ int ssam_notifier_register(struct ssam_controller *ctrl, struct ssam_event_notif
EXPORT_SYMBOL_GPL(ssam_notifier_register);
/**
- * ssam_notifier_unregister() - Unregister an event notifier.
- * @ctrl: The controller the notifier has been registered on.
- * @n: The event notifier to unregister.
+ * __ssam_notifier_unregister() - Unregister an event notifier.
+ * @ctrl: The controller the notifier has been registered on.
+ * @n: The event notifier to unregister.
+ * @disable: Whether to disable the corresponding event on the EC.
*
* Unregister an event notifier. Decrement the usage counter of the associated
* SAM event if the notifier is not marked as an observer. If the usage counter
- * reaches zero, the event will be disabled.
+ * reaches zero and ``disable`` equals ``true``, the event will be disabled.
+ *
+ * Useful for hot-removable devices, where communication may fail once the
+ * device has been physically removed. In that case, specifying ``disable`` as
+ * ``false`` avoids communication with the EC.
*
* Return: Returns zero on success, %-ENOENT if the given notifier block has
* not been registered on the controller. If the given notifier block was the
* last one associated with its specific event, returns the status of the
* event-disable EC-command.
*/
-int ssam_notifier_unregister(struct ssam_controller *ctrl, struct ssam_event_notifier *n)
+int __ssam_notifier_unregister(struct ssam_controller *ctrl, struct ssam_event_notifier *n,
+ bool disable)
{
u16 rqid = ssh_tc_to_rqid(n->event.id.target_category);
struct ssam_nf_refcount_entry *entry;
@@ -2373,7 +2390,7 @@ int ssam_notifier_unregister(struct ssam_controller *ctrl, struct ssam_event_not
goto remove;
}
- status = ssam_nf_refcount_disable_free(ctrl, entry, n->event.flags);
+ status = ssam_nf_refcount_disable_free(ctrl, entry, n->event.flags, disable);
}
remove:
@@ -2383,7 +2400,7 @@ int ssam_notifier_unregister(struct ssam_controller *ctrl, struct ssam_event_not
return status;
}
-EXPORT_SYMBOL_GPL(ssam_notifier_unregister);
+EXPORT_SYMBOL_GPL(__ssam_notifier_unregister);
/**
* ssam_controller_event_enable() - Enable the specified event.
@@ -2477,7 +2494,7 @@ int ssam_controller_event_disable(struct ssam_controller *ctrl,
return -ENOENT;
}
- status = ssam_nf_refcount_disable_free(ctrl, entry, flags);
+ status = ssam_nf_refcount_disable_free(ctrl, entry, flags, true);
mutex_unlock(&nf->lock);
return status;
diff --git a/include/linux/surface_aggregator/controller.h b/include/linux/surface_aggregator/controller.h
index 74bfdffaf7b0..50a2b4926c06 100644
--- a/include/linux/surface_aggregator/controller.h
+++ b/include/linux/surface_aggregator/controller.h
@@ -835,8 +835,28 @@ struct ssam_event_notifier {
int ssam_notifier_register(struct ssam_controller *ctrl,
struct ssam_event_notifier *n);
-int ssam_notifier_unregister(struct ssam_controller *ctrl,
- struct ssam_event_notifier *n);
+int __ssam_notifier_unregister(struct ssam_controller *ctrl,
+ struct ssam_event_notifier *n, bool disable);
+
+/**
+ * ssam_notifier_unregister() - Unregister an event notifier.
+ * @ctrl: The controller the notifier has been registered on.
+ * @n: The event notifier to unregister.
+ *
+ * Unregister an event notifier. Decrement the usage counter of the associated
+ * SAM event if the notifier is not marked as an observer. If the usage counter
+ * reaches zero, the event will be disabled.
+ *
+ * Return: Returns zero on success, %-ENOENT if the given notifier block has
+ * not been registered on the controller. If the given notifier block was the
+ * last one associated with its specific event, returns the status of the
+ * event-disable EC-command.
+ */
+static inline int ssam_notifier_unregister(struct ssam_controller *ctrl,
+ struct ssam_event_notifier *n)
+{
+ return __ssam_notifier_unregister(ctrl, n, true);
+}
int ssam_controller_event_enable(struct ssam_controller *ctrl,
struct ssam_event_registry reg,
diff --git a/include/linux/surface_aggregator/device.h b/include/linux/surface_aggregator/device.h
index 491aa7e9f4bc..ad245c6b00d0 100644
--- a/include/linux/surface_aggregator/device.h
+++ b/include/linux/surface_aggregator/device.h
@@ -472,4 +472,70 @@ static inline void ssam_remove_clients(struct device *dev) {}
sdev->uid.instance, ret); \
}
+
+/* -- Helpers for client-device notifiers. ---------------------------------- */
+
+/**
+ * ssam_device_notifier_register() - Register an event notifier for the
+ * specified client device.
+ * @sdev: The device the notifier should be registered on.
+ * @n: The event notifier to register.
+ *
+ * Register an event notifier. Increment the usage counter of the associated
+ * SAM event if the notifier is not marked as an observer. If the event is not
+ * marked as an observer and is currently not enabled, it will be enabled
+ * during this call. If the notifier is marked as an observer, no attempt will
+ * be made at enabling any event and no reference count will be modified.
+ *
+ * Notifiers marked as observers do not need to be associated with one specific
+ * event, i.e. as long as no event matching is performed, only the event target
+ * category needs to be set.
+ *
+ * Return: Returns zero on success, %-ENOSPC if there have already been
+ * %INT_MAX notifiers for the event ID/type associated with the notifier block
+ * registered, %-ENOMEM if the corresponding event entry could not be
+ * allocated, %-ENODEV if the device is marked as hot-removed. If this is the
+ * first time that a notifier block is registered for the specific associated
+ * event, returns the status of the event-enable EC-command.
+ */
+static inline int ssam_device_notifier_register(struct ssam_device *sdev,
+ struct ssam_event_notifier *n)
+{
+ /*
+ * Note that this check does not provide any guarantees whatsoever as
+ * hot-removal could happen at any point and we can't protect against
+ * it. Nevertheless, if we can detect hot-removal, bail early to avoid
+ * communication timeouts.
+ */
+ if (ssam_device_is_hot_removed(sdev))
+ return -ENODEV;
+
+ return ssam_notifier_register(sdev->ctrl, n);
+}
+
+/**
+ * ssam_device_notifier_unregister() - Unregister an event notifier for the
+ * specified client device.
+ * @sdev: The device the notifier has been registered on.
+ * @n: The event notifier to unregister.
+ *
+ * Unregister an event notifier. Decrement the usage counter of the associated
+ * SAM event if the notifier is not marked as an observer. If the usage counter
+ * reaches zero, the event will be disabled.
+ *
+ * In case the device has been marked as hot-removed, the event will not be
+ * disabled on the EC, as in those cases any attempt at doing so may time out.
+ *
+ * Return: Returns zero on success, %-ENOENT if the given notifier block has
+ * not been registered on the controller. If the given notifier block was the
+ * last one associated with its specific event, returns the status of the
+ * event-disable EC-command.
+ */
+static inline int ssam_device_notifier_unregister(struct ssam_device *sdev,
+ struct ssam_event_notifier *n)
+{
+ return __ssam_notifier_unregister(sdev->ctrl, n,
+ !ssam_device_is_hot_removed(sdev));
+}
+
#endif /* _LINUX_SURFACE_AGGREGATOR_DEVICE_H */
--
2.36.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 06/10] HID: surface-hid: Add support for hot-removal
2022-05-20 18:34 [PATCH 00/10] platform/surface: aggregator: Add support for client hot-removal Maximilian Luz
2022-05-20 18:34 ` [PATCH 01/10] platform/surface: aggregator: Allow devices to be marked as hot-removed Maximilian Luz
2022-05-20 18:34 ` [PATCH 02/10] platform/surface: aggregator: Allow notifiers to avoid communication on unregistering Maximilian Luz
@ 2022-05-20 18:34 ` Maximilian Luz
2022-05-26 23:55 ` kernel test robot
2 siblings, 1 reply; 5+ messages in thread
From: Maximilian Luz @ 2022-05-20 18:34 UTC (permalink / raw)
To: Hans de Goede, Jiri Kosina
Cc: Maximilian Luz, Mark Gross, Benjamin Tissoires,
platform-driver-x86, linux-input, linux-kernel
Add support for hot-removal of SSAM HID client devices.
Once a device has been hot-removed, further communication with it should
be avoided as it may fail and time out. While the device will be removed
as soon as we detect hot-removal, communication may still occur during
teardown, especially when unregistering notifiers.
While hot-removal is a surprise event that can happen at any time, try
to avoid communication as much as possible once it has been detected to
prevent timeouts that can slow down device removal and cause issues,
e.g. when quickly re-attaching the device.
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
---
drivers/hid/surface-hid/surface_hid_core.c | 38 +++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/drivers/hid/surface-hid/surface_hid_core.c b/drivers/hid/surface-hid/surface_hid_core.c
index e46330b2e561..87637f813de2 100644
--- a/drivers/hid/surface-hid/surface_hid_core.c
+++ b/drivers/hid/surface-hid/surface_hid_core.c
@@ -19,12 +19,30 @@
#include "surface_hid_core.h"
+/* -- Utility functions. ---------------------------------------------------- */
+
+static bool surface_hid_is_hot_removed(struct surface_hid_device *shid)
+{
+ /*
+ * Non-ssam client devices, i.e. platform client devices, cannot be
+ * hot-removed.
+ */
+ if (!is_ssam_device(shid->dev))
+ return false;
+
+ return ssam_device_is_hot_removed(to_ssam_device(shid->dev));
+}
+
+
/* -- Device descriptor access. --------------------------------------------- */
static int surface_hid_load_hid_descriptor(struct surface_hid_device *shid)
{
int status;
+ if (surface_hid_is_hot_removed(shid))
+ return -ENODEV;
+
status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_HID,
(u8 *)&shid->hid_desc, sizeof(shid->hid_desc));
if (status)
@@ -61,6 +79,9 @@ static int surface_hid_load_device_attributes(struct surface_hid_device *shid)
{
int status;
+ if (surface_hid_is_hot_removed(shid))
+ return -ENODEV;
+
status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_ATTRS,
(u8 *)&shid->attrs, sizeof(shid->attrs));
if (status)
@@ -88,9 +109,18 @@ static int surface_hid_start(struct hid_device *hid)
static void surface_hid_stop(struct hid_device *hid)
{
struct surface_hid_device *shid = hid->driver_data;
+ bool hot_removed;
+
+ /*
+ * Communication may fail for devices that have been hot-removed. This
+ * also includes unregistration of HID events, so we need to check this
+ * here. Only if the device has not been marked as hot-removed, we can
+ * safely disable events.
+ */
+ hot_removed = surface_hid_is_hot_removed(shid);
/* Note: This call will log errors for us, so ignore them here. */
- ssam_notifier_unregister(shid->ctrl, &shid->notif);
+ __ssam_notifier_unregister(shid->ctrl, &shid->notif, !hot_removed);
}
static int surface_hid_open(struct hid_device *hid)
@@ -109,6 +139,9 @@ static int surface_hid_parse(struct hid_device *hid)
u8 *buf;
int status;
+ if (surface_hid_is_hot_removed(shid))
+ return -ENODEV;
+
buf = kzalloc(len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
@@ -126,6 +159,9 @@ static int surface_hid_raw_request(struct hid_device *hid, unsigned char reportn
{
struct surface_hid_device *shid = hid->driver_data;
+ if (surface_hid_is_hot_removed(shid))
+ return -ENODEV;
+
if (rtype == HID_OUTPUT_REPORT && reqtype == HID_REQ_SET_REPORT)
return shid->ops.output_report(shid, reportnum, buf, len);
--
2.36.1
^ permalink raw reply related [flat|nested] 5+ messages in thread