[PATCH v9] uvcvideo: send a control event when a Control Change interrupt arrives

Guennadi Liakhovetski
2018-07-26T09:33:41Z

From: Guennadi Liakhovetski <guennadi.liakhovetski@intel.com>

UVC defines a method of handling asynchronous controls, which sends a
USB packet over the interrupt pipe. This patch implements support for
such packets by sending a control event to the user. Since this can
involve USB traffic and, therefore, scheduling, this has to be done
in a work queue.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@intel.com>
---

v9:
- multiple optimisations and style improvements from Laurent - thanks
- avoid the handle rewriting race at least in cases, when the user only
sends a new control after receiving an event for the previous one

Laurent, you added a couple of comments, using DocBook markup like
"@param" but you didn't mark those comments for DocBook processing with
"/**" - I don't care that much, just wanted to check, that that was
intentional.

drivers/media/usb/uvc/uvc_ctrl.c | 211 ++++++++++++++++++++++++++++---------
drivers/media/usb/uvc/uvc_status.c | 121 ++++++++++++++++++---
drivers/media/usb/uvc/uvc_v4l2.c | 4 +-
drivers/media/usb/uvc/uvcvideo.h | 15 ++-
include/uapi/linux/uvcvideo.h | 2 +
5 files changed, 286 insertions(+), 67 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 2a213c8..ddd069b 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -20,6 +20,7 @@
#include <linux/videodev2.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
+#include <linux/workqueue.h>
#include <linux/atomic.h>
#include <media/v4l2-ctrls.h>

@@ -971,12 +972,30 @@ static int uvc_ctrl_populate_cache(struct uvc_video_chain *chain,
return 0;
}

+static s32 __uvc_ctrl_get_value(struct uvc_control_mapping *mapping,
+ const u8 *data)
+{
+ s32 value = mapping->get(mapping, UVC_GET_CUR, data);
+
+ if (mapping->v4l2_type == V4L2_CTRL_TYPE_MENU) {
+ struct uvc_menu_info *menu = mapping->menu_info;
+ unsigned int i;
+
+ for (i = 0; i < mapping->menu_count; ++i, ++menu) {
+ if (menu->value == value) {
+ value = i;
+ break;
+ }
+ }
+ }
+
+ return value;
+}
+
static int __uvc_ctrl_get(struct uvc_video_chain *chain,
struct uvc_control *ctrl, struct uvc_control_mapping *mapping,
s32 *value)
{
- struct uvc_menu_info *menu;
- unsigned int i;
int ret;

if ((ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR) == 0)
@@ -993,18 +1012,8 @@ static int __uvc_ctrl_get(struct uvc_video_chain *chain,
ctrl->loaded = 1;
}

- *value = mapping->get(mapping, UVC_GET_CUR,
- uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));
-
- if (mapping->v4l2_type == V4L2_CTRL_TYPE_MENU) {
- menu = mapping->menu_info;
- for (i = 0; i < mapping->menu_count; ++i, ++menu) {
- if (menu->value == *value) {
- *value = i;
- break;
- }
- }
- }
+ *value = __uvc_ctrl_get_value(mapping,
+ uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));

return 0;
}
@@ -1216,53 +1225,135 @@ static void uvc_ctrl_fill_event(struct uvc_video_chain *chain,
ev->u.ctrl.default_value = v4l2_ctrl.default_value;
}

-static void uvc_ctrl_send_event(struct uvc_fh *handle,
- struct uvc_control *ctrl, struct uvc_control_mapping *mapping,
- s32 value, u32 changes)
+/*
+ * Send control change events to all subscribers for the @ctrl control. By
+ * default the subscriber that generated the event, as identified by @handle,
+ * is not notified unless it has set the V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK flag.
+ * @handle can be NULL for asynchronous events related to auto-update controls,
+ * in which case all subscribers are notified.
+ */
+static void uvc_ctrl_send_event(struct uvc_video_chain *chain,
+ struct uvc_fh *handle, struct uvc_control *ctrl,
+ struct uvc_control_mapping *mapping, s32 value, u32 changes)
{
+ struct v4l2_fh *originator = handle ? &handle->vfh : NULL;
struct v4l2_subscribed_event *sev;
struct v4l2_event ev;

if (list_empty(&mapping->ev_subs))
return;

- uvc_ctrl_fill_event(handle->chain, &ev, ctrl, mapping, value, changes);
+ uvc_ctrl_fill_event(chain, &ev, ctrl, mapping, value, changes);

list_for_each_entry(sev, &mapping->ev_subs, node) {
- if (sev->fh != &handle->vfh ||
+ if (sev->fh != originator ||
(sev->flags & V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK) ||
(changes & V4L2_EVENT_CTRL_CH_FLAGS))
v4l2_event_queue_fh(sev->fh, &ev);
}
}

-static void uvc_ctrl_send_slave_event(struct uvc_fh *handle,
- struct uvc_control *master, u32 slave_id,
- const struct v4l2_ext_control *xctrls, unsigned int xctrls_count)
+/*
+ * Send control change events for the slave of the @master control identified
+ * by the V4L2 ID @slave_id. The @handle identifies the event subscriber that
+ * generated the event and may be NULL for auto-update events.
+ */
+static void uvc_ctrl_send_slave_event(struct uvc_video_chain *chain,
+ struct uvc_fh *handle, struct uvc_control *master, u32 slave_id)
{
struct uvc_control_mapping *mapping = NULL;
struct uvc_control *ctrl = NULL;
u32 changes = V4L2_EVENT_CTRL_CH_FLAGS;
- unsigned int i;
s32 val = 0;

- /*
- * We can skip sending an event for the slave if the slave
- * is being modified in the same transaction.
- */
- for (i = 0; i < xctrls_count; i++) {
- if (xctrls[i].id == slave_id)
- return;
- }
-
__uvc_find_control(master->entity, slave_id, &mapping, &ctrl, 0);
if (ctrl == NULL)
return;

- if (__uvc_ctrl_get(handle->chain, ctrl, mapping, &val) == 0)
+ if (__uvc_ctrl_get(chain, ctrl, mapping, &val) == 0)
changes |= V4L2_EVENT_CTRL_CH_VALUE;

- uvc_ctrl_send_event(handle, ctrl, mapping, val, changes);
+ uvc_ctrl_send_event(chain, handle, ctrl, mapping, val, changes);
+}
+
+static void uvc_ctrl_status_event_work(struct work_struct *work)
+{
+ struct uvc_device *dev = container_of(work, struct uvc_device,
+ async_ctrl.work);
+ struct uvc_ctrl_work *w = &dev->async_ctrl;
+ struct uvc_video_chain *chain = w->chain;
+ struct uvc_control_mapping *mapping;
+ struct uvc_control *ctrl = w->ctrl;
+ struct uvc_fh *handle;
+ unsigned int i;
+ int ret;
+
+ mutex_lock(&chain->ctrl_mutex);
+
+ handle = ctrl->handle;
+ ctrl->handle = NULL;
+
+ list_for_each_entry(mapping, &ctrl->info.mappings, list) {
+ s32 value = __uvc_ctrl_get_value(mapping, w->data);
+
+ /*
+ * handle may be NULL here if the device sends auto-update
+ * events without a prior related control set from userspace.
+ */
+ for (i = 0; i < ARRAY_SIZE(mapping->slave_ids); ++i) {
+ if (!mapping->slave_ids[i])
+ break;
+
+ uvc_ctrl_send_slave_event(chain, handle, ctrl,
+ mapping->slave_ids[i]);
+ }
+
+ uvc_ctrl_send_event(chain, handle, ctrl, mapping, value,
+ V4L2_EVENT_CTRL_CH_VALUE);
+ }
+
+ mutex_unlock(&chain->ctrl_mutex);
+
+ /* Resubmit the URB. */
+ w->urb->interval = dev->int_ep->desc.bInterval;
+ ret = usb_submit_urb(w->urb, GFP_KERNEL);
+ if (ret < 0)
+ uvc_printk(KERN_ERR, "Failed to resubmit status URB (%d).\n",
+ ret);
+}
+
+bool uvc_ctrl_status_event(struct urb *urb, struct uvc_video_chain *chain,
+ struct uvc_control *ctrl, const u8 *data)
+{
+ struct uvc_device *dev = chain->dev;
+ struct uvc_ctrl_work *w = &dev->async_ctrl;
+
+ if (list_empty(&ctrl->info.mappings)) {
+ ctrl->handle = NULL;
+ return false;
+ }
+
+ w->data = data;
+ w->urb = urb;
+ w->chain = chain;
+ w->ctrl = ctrl;
+
+ schedule_work(&w->work);
+
+ return true;
+}
+
+static bool uvc_ctrl_xctrls_has_control(const struct v4l2_ext_control *xctrls,
+ unsigned int xctrls_count, u32 id)
+{
+ unsigned int i;
+
+ for (i = 0; i < xctrls_count; ++i) {
+ if (xctrls[i].id == id)
+ return true;
+ }
+
+ return false;
}

static void uvc_ctrl_send_events(struct uvc_fh *handle,
@@ -1277,29 +1368,39 @@ static void uvc_ctrl_send_events(struct uvc_fh *handle,
for (i = 0; i < xctrls_count; ++i) {
ctrl = uvc_find_control(handle->chain, xctrls[i].id, &mapping);

+ if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS)
+ /* Notification will be sent from an Interrupt event. */
+ continue;
+
for (j = 0; j < ARRAY_SIZE(mapping->slave_ids); ++j) {
- if (!mapping->slave_ids[j])
+ u32 slave_id = mapping->slave_ids[j];
+
+ if (!slave_id)
break;
- uvc_ctrl_send_slave_event(handle, ctrl,
- mapping->slave_ids[j],
- xctrls, xctrls_count);
+
+ /*
+ * We can skip sending an event for the slave if the
+ * slave is being modified in the same transaction.
+ */
+ if (uvc_ctrl_xctrls_has_control(xctrls, xctrls_count,
+ slave_id))
+ continue;
+
+ uvc_ctrl_send_slave_event(handle->chain, handle, ctrl,
+ slave_id);
}

/*
* If the master is being modified in the same transaction
* flags may change too.
*/
- if (mapping->master_id) {
- for (j = 0; j < xctrls_count; j++) {
- if (xctrls[j].id == mapping->master_id) {
- changes |= V4L2_EVENT_CTRL_CH_FLAGS;
- break;
- }
- }
- }
+ if (mapping->master_id &&
+ uvc_ctrl_xctrls_has_control(xctrls, xctrls_count,
+ mapping->master_id))
+ changes |= V4L2_EVENT_CTRL_CH_FLAGS;

- uvc_ctrl_send_event(handle, ctrl, mapping, xctrls[i].value,
- changes);
+ uvc_ctrl_send_event(handle->chain, handle, ctrl, mapping,
+ xctrls[i].value, changes);
}
}

@@ -1472,9 +1573,10 @@ int uvc_ctrl_get(struct uvc_video_chain *chain,
return __uvc_ctrl_get(chain, ctrl, mapping, &xctrl->value);
}

-int uvc_ctrl_set(struct uvc_video_chain *chain,
+int uvc_ctrl_set(struct uvc_fh *handle,
struct v4l2_ext_control *xctrl)
{
+ struct uvc_video_chain *chain = handle->chain;
struct uvc_control *ctrl;
struct uvc_control_mapping *mapping;
s32 value;
@@ -1581,6 +1683,9 @@ int uvc_ctrl_set(struct uvc_video_chain *chain,
mapping->set(mapping, value,
uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));

+ if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS)
+ ctrl->handle = handle;
+
ctrl->dirty = 1;
ctrl->modified = 1;
return 0;
@@ -1612,7 +1717,9 @@ static int uvc_ctrl_get_flags(struct uvc_device *dev,
| (data[0] & UVC_CONTROL_CAP_SET ?
UVC_CTRL_FLAG_SET_CUR : 0)
| (data[0] & UVC_CONTROL_CAP_AUTOUPDATE ?
- UVC_CTRL_FLAG_AUTO_UPDATE : 0);
+ UVC_CTRL_FLAG_AUTO_UPDATE : 0)
+ | (data[0] & UVC_CONTROL_CAP_ASYNCHRONOUS ?
+ UVC_CTRL_FLAG_ASYNCHRONOUS : 0);

kfree(data);
return ret;
@@ -2173,6 +2280,8 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
struct uvc_entity *entity;
unsigned int i;

+ INIT_WORK(&dev->async_ctrl.work, uvc_ctrl_status_event_work);
+
/* Walk the entities list and instantiate controls */
list_for_each_entry(entity, &dev->entities, list) {
struct uvc_control *ctrl;
@@ -2241,6 +2350,8 @@ void uvc_ctrl_cleanup_device(struct uvc_device *dev)
struct uvc_entity *entity;
unsigned int i;

+ cancel_work_sync(&dev->async_ctrl.work);
+
/* Free controls and control mappings for all entities. */
list_for_each_entry(entity, &dev->entities, list) {
for (i = 0; i < entity->ncontrols; ++i) {
diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
index 7b71041..0722dc6 100644
--- a/drivers/media/usb/uvc/uvc_status.c
+++ b/drivers/media/usb/uvc/uvc_status.c
@@ -78,7 +78,24 @@ static void uvc_input_report_key(struct uvc_device *dev, unsigned int code,
/* --------------------------------------------------------------------------
* Status interrupt endpoint
*/
-static void uvc_event_streaming(struct uvc_device *dev, u8 *data, int len)
+struct uvc_streaming_status {
+ u8 bStatusType;
+ u8 bOriginator;
+ u8 bEvent;
+ u8 bValue[];
+} __packed;
+
+struct uvc_control_status {
+ u8 bStatusType;
+ u8 bOriginator;
+ u8 bEvent;
+ u8 bSelector;
+ u8 bAttribute;
+ u8 bValue[];
+} __packed;
+
+static void uvc_event_streaming(struct uvc_device *dev,
+ struct uvc_streaming_status *status, int len)
{
if (len < 3) {
uvc_trace(UVC_TRACE_STATUS, "Invalid streaming status event "
@@ -86,31 +103,97 @@ static void uvc_event_streaming(struct uvc_device *dev, u8 *data, int len)
return;
}

- if (data[2] == 0) {
+ if (status->bEvent == 0) {
if (len < 4)
return;
uvc_trace(UVC_TRACE_STATUS, "Button (intf %u) %s len %d\n",
- data[1], data[3] ? "pressed" : "released", len);
- uvc_input_report_key(dev, KEY_CAMERA, data[3]);
+ status->bOriginator,
+ status->bValue[0] ? "pressed" : "released", len);
+ uvc_input_report_key(dev, KEY_CAMERA, status->bValue[0]);
} else {
uvc_trace(UVC_TRACE_STATUS,
"Stream %u error event %02x len %d.\n",
- data[1], data[2], len);
+ status->bOriginator, status->bEvent, len);
}
}

-static void uvc_event_control(struct uvc_device *dev, u8 *data, int len)
+#define UVC_CTRL_VALUE_CHANGE 0
+#define UVC_CTRL_INFO_CHANGE 1
+#define UVC_CTRL_FAILURE_CHANGE 2
+#define UVC_CTRL_MIN_CHANGE 3
+#define UVC_CTRL_MAX_CHANGE 4
+
+static struct uvc_control *uvc_event_entity_find_ctrl(struct uvc_entity *entity,
+ u8 selector)
{
- char *attrs[3] = { "value", "info", "failure" };
+ struct uvc_control *ctrl;
+ unsigned int i;
+
+ for (i = 0, ctrl = entity->controls; i < entity->ncontrols; i++, ctrl++)
+ if (ctrl->info.selector == selector)
+ return ctrl;
+
+ return NULL;
+}

- if (len < 6 || data[2] != 0 || data[4] > 2) {
+static struct uvc_control *uvc_event_find_ctrl(struct uvc_device *dev,
+ const struct uvc_control_status *status,
+ struct uvc_video_chain **chain)
+{
+ list_for_each_entry((*chain), &dev->chains, list) {
+ struct uvc_entity *entity;
+ struct uvc_control *ctrl;
+
+ list_for_each_entry(entity, &(*chain)->entities, chain) {
+ if (entity->id != status->bOriginator)
+ continue;
+
+ ctrl = uvc_event_entity_find_ctrl(entity,
+ status->bSelector);
+ if (ctrl)
+ return ctrl;
+ }
+ }
+
+ return NULL;
+}
+
+static bool uvc_event_control(struct urb *urb,
+ const struct uvc_control_status *status, int len)
+{
+ static const char *attrs[] = { "value", "info", "failure", "min", "max" };
+ struct uvc_device *dev = urb->context;
+ struct uvc_video_chain *chain;
+ struct uvc_control *ctrl;
+
+ if (len < 6 || status->bEvent != 0 ||
+ status->bAttribute >= ARRAY_SIZE(attrs)) {
uvc_trace(UVC_TRACE_STATUS, "Invalid control status event "
"received.\n");
- return;
+ return false;
}

uvc_trace(UVC_TRACE_STATUS, "Control %u/%u %s change len %d.\n",
- data[1], data[3], attrs[data[4]], len);
+ status->bOriginator, status->bSelector,
+ attrs[status->bAttribute], len);
+
+ /* Find the control. */
+ ctrl = uvc_event_find_ctrl(dev, status, &chain);
+ if (!ctrl)
+ return false;
+
+ switch (status->bAttribute) {
+ case UVC_CTRL_VALUE_CHANGE:
+ return uvc_ctrl_status_event(urb, chain, ctrl, status->bValue);
+
+ case UVC_CTRL_INFO_CHANGE:
+ case UVC_CTRL_FAILURE_CHANGE:
+ case UVC_CTRL_MIN_CHANGE:
+ case UVC_CTRL_MAX_CHANGE:
+ break;
+ }
+
+ return false;
}

static void uvc_status_complete(struct urb *urb)
@@ -138,13 +221,23 @@ static void uvc_status_complete(struct urb *urb)
len = urb->actual_length;
if (len > 0) {
switch (dev->status[0] & 0x0f) {
- case UVC_STATUS_TYPE_CONTROL:
- uvc_event_control(dev, dev->status, len);
+ case UVC_STATUS_TYPE_CONTROL: {
+ struct uvc_control_status *status =
+ (struct uvc_control_status *)dev->status;
+
+ if (uvc_event_control(urb, status, len))
+ /* The URB will be resubmitted in work context. */
+ return;
break;
+ }

- case UVC_STATUS_TYPE_STREAMING:
- uvc_event_streaming(dev, dev->status, len);
+ case UVC_STATUS_TYPE_STREAMING: {
+ struct uvc_streaming_status *status =
+ (struct uvc_streaming_status *)dev->status;
+
+ uvc_event_streaming(dev, status, len);
break;
+ }

default:
uvc_trace(UVC_TRACE_STATUS, "Unknown status event "
diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index bd32914..18a7384 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -994,7 +994,7 @@ static int uvc_ioctl_s_ctrl(struct file *file, void *fh,
if (ret < 0)
return ret;

- ret = uvc_ctrl_set(chain, &xctrl);
+ ret = uvc_ctrl_set(handle, &xctrl);
if (ret < 0) {
uvc_ctrl_rollback(handle);
return ret;
@@ -1069,7 +1069,7 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
return ret;

for (i = 0; i < ctrls->count; ++ctrl, ++i) {
- ret = uvc_ctrl_set(chain, ctrl);
+ ret = uvc_ctrl_set(handle, ctrl);
if (ret < 0) {
uvc_ctrl_rollback(handle);
ctrls->error_idx = commit ? ctrls->count : i;
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index be5cf17..8ae03a4 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -12,6 +12,7 @@
#include <linux/usb/video.h>
#include <linux/uvcvideo.h>
#include <linux/videodev2.h>
+#include <linux/workqueue.h>
#include <media/media-device.h>
#include <media/v4l2-device.h>
#include <media/v4l2-event.h>
@@ -256,6 +257,8 @@ struct uvc_control {
initialized:1;

u8 *uvc_data;
+
+ struct uvc_fh *handle; /* File handle that last changed the control. */
};

struct uvc_format_desc {
@@ -600,6 +603,14 @@ struct uvc_device {
u8 *status;
struct input_dev *input;
char input_phys[64];
+
+ struct uvc_ctrl_work {
+ struct work_struct work;
+ struct urb *urb;
+ struct uvc_video_chain *chain;
+ struct uvc_control *ctrl;
+ const void *data;
+ } async_ctrl;
};

enum uvc_handle_state {
@@ -753,6 +764,8 @@ int uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
int uvc_ctrl_init_device(struct uvc_device *dev);
void uvc_ctrl_cleanup_device(struct uvc_device *dev);
int uvc_ctrl_restore_values(struct uvc_device *dev);
+bool uvc_ctrl_status_event(struct urb *urb, struct uvc_video_chain *chain,
+ struct uvc_control *ctrl, const u8 *data);

int uvc_ctrl_begin(struct uvc_video_chain *chain);
int __uvc_ctrl_commit(struct uvc_fh *handle, int rollback,
@@ -770,7 +783,7 @@ static inline int uvc_ctrl_rollback(struct uvc_fh *handle)
}

int uvc_ctrl_get(struct uvc_video_chain *chain, struct v4l2_ext_control *xctrl);
-int uvc_ctrl_set(struct uvc_video_chain *chain, struct v4l2_ext_control *xctrl);
+int uvc_ctrl_set(struct uvc_fh *handle, struct v4l2_ext_control *xctrl);

int uvc_xu_ctrl_query(struct uvc_video_chain *chain,
struct uvc_xu_control_query *xqry);
diff --git a/include/uapi/linux/uvcvideo.h b/include/uapi/linux/uvcvideo.h
index 020714d..f80f05b 100644
--- a/include/uapi/linux/uvcvideo.h
+++ b/include/uapi/linux/uvcvideo.h
@@ -28,6 +28,8 @@
#define UVC_CTRL_FLAG_RESTORE (1 << 6)
/* Control can be updated by the camera. */
#define UVC_CTRL_FLAG_AUTO_UPDATE (1 << 7)
+/* Control supports asynchronous reporting */
+#define UVC_CTRL_FLAG_ASYNCHRONOUS (1 << 8)

#define UVC_CTRL_FLAG_GET_RANGE \
(UVC_CTRL_FLAG_GET_CUR | UVC_CTRL_FLAG_GET_MIN | \
--
1.9.3