@@ -1097,7 +1097,7 @@ int hid_input_report(struct hid_device *hid, int
type, u8 *data, int size, int i
if (!hid)
return -ENODEV;
- if (down_trylock(&hid->driver_lock))
+ if (down_trylock(&hid->driver_input_lock))
return -EBUSY;
if (!hid->driver) {
@@ -1150,7 +1150,7 @@ nomem:
hid_report_raw_event(hid, type, data, size, interrupt);
unlock:
- up(&hid->driver_lock);
+ up(&hid->driver_input_lock);
return ret;
}
EXPORT_SYMBOL_GPL(hid_input_report);
@@ -1703,6 +1703,11 @@ static int hid_device_probe(struct device *dev)
if (down_interruptible(&hdev->driver_lock))
return -EINTR;
+ if (down_interruptible(&hdev->driver_input_lock)) {
+ ret = -EINTR;
+ goto unlock_driver_lock;
+ }
+ hdev->io_started = false;
if (!hdev->driver) {
id = hid_match_device(hdev, hdrv);
@@ -1726,6 +1731,9 @@ static int hid_device_probe(struct device *dev)
hdev->driver = NULL;
}
unlock:
+ if (!hdev->io_started)
+ up(&hdev->driver_input_lock);
+unlock_driver_lock:
up(&hdev->driver_lock);
return ret;
}
@@ -1734,9 +1742,15 @@ static int hid_device_remove(struct device *dev)
{
struct hid_device *hdev = container_of(dev, struct hid_device, dev);
struct hid_driver *hdrv;
+ int ret = 0;
if (down_interruptible(&hdev->driver_lock))
return -EINTR;
+ if (down_interruptible(&hdev->driver_input_lock)) {
+ ret = -EINTR;
+ goto unlock_driver_lock;
+ }
+ hdev->io_started = false;
hdrv = hdev->driver;
if (hdrv) {
@@ -1747,8 +1761,11 @@ static int hid_device_remove(struct device *dev)
hdev->driver = NULL;
}
+ if (!hdev->io_started)
+ up(&hdev->driver_input_lock);
+unlock_driver_lock:
up(&hdev->driver_lock);
- return 0;
+ return ret;
}
static int hid_uevent(struct device *dev, struct kobj_uevent_env *env)
@@ -2126,6 +2143,7 @@ struct hid_device *hid_allocate_device(void)
init_waitqueue_head(&hdev->debug_wait);
INIT_LIST_HEAD(&hdev->debug_list);
sema_init(&hdev->driver_lock, 1);
+ sema_init(&hdev->driver_input_lock, 1);
return hdev;
err:
@@ -481,7 +481,8 @@ struct hid_device { /* device report descriptor */
unsigned country; /* HID country */
struct hid_report_enum report_enum[HID_REPORT_TYPES];
- struct semaphore driver_lock; /* protects the current driver */
+ struct semaphore driver_lock; /* protects the current driver,
except during input */
+ struct semaphore driver_input_lock; /* protects the current driver */
struct device dev; /* device */
struct hid_driver *driver;
This version incorporates the warning for drivers that use io_start()/stop() in an unbalanced way. It is otherwise unchanged from the previous version. Let me know if there are any other comments/issues. Thanks, -andrew This patch separates struct hid_device's driver_lock into two. The goal is to allow hid device drivers to receive input during their probe() or remove() function calls. This is necessary because some drivers need to communicate with the device to determine parameters needed during probe (e.g., size of a multi-touch surface), and if possible, may perfer to communicate with a device on host-initiated disconnect (e.g., to put it into a low-power state). Historically, three functions used driver_lock: - hid_device_probe: blocks to acquire lock - hid_device_remove: blocks to acquire lock - hid_input_report: if locked returns -EBUSY, else acquires lock This patch adds another lock (driver_input_lock) which is used to block input from occurring. The lock behavior is now: - hid_device_probe: blocks to acq. driver_lock, then driver_input_lock - hid_device_remove: blocks to acq. driver_lock, then driver_input_lock - hid_input_report: if driver_input_lock locked returns -EBUSY, else acquires driver_input_lock This patch also adds two helper functions to be called during probe() or remove(): hid_device_io_start() and hid_device_io_stop(). These functions lock and unlock, respectively, driver_input_lock; they also make a note of whether they did so that hid-core knows if a driver has changed the lock state. This patch results in no behavior change for existing devices and drivers. However, during a probe() or remove() function call in a driver, that driver may now selectively call hid_device_io_start() to let input events come through, then optionally call hid_device_io_stop() to stop them. Change-Id: I737f6fc15911134b51273acf8d3de92fa5cc0f85 --- drivers/hid/hid-core.c | 24 +++++++++++++++++++++--- include/linux/hid.h | 46 +++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 66 insertions(+), 4 deletions(-) struct hid_ll_driver *ll_driver; @@ -502,6 +503,7 @@ struct hid_device { /* device report descriptor */ unsigned int status; /* see STAT flags above */ unsigned claimed; /* Claimed by hidinput, hiddev? */ unsigned quirks; /* Various quirks the device can pull on us */ + bool io_started; /* Protected by driver_lock. If IO has started */ struct list_head inputs; /* The list of inputs */ void *hiddev; /* The hiddev structure */ @@ -622,6 +624,10 @@ struct hid_usage_id { * @resume: invoked on resume if device was not reset (NULL means nop) * @reset_resume: invoked on resume if device was reset (NULL means nop) * + * probe should return -errno on error, or 0 on success. During probe, + * input will not be passed to raw_event unless hid_device_io_start is + * called. + * * raw_event and event should return 0 on no action performed, 1 when no * further processing should be done and negative on error * @@ -742,6 +748,44 @@ const struct hid_device_id *hid_match_id(struct hid_device *hdev, const struct hid_device_id *id); /** + * hid_device_io_start - enable HID input during probe, remove + * + * @hid - the device + * + * This should only be called during probe or remove and only be + * called by the thread calling probe or remove. It will allow + * incoming packets to be delivered to the driver. + */ +static inline void hid_device_io_start(struct hid_device *hid) { + if (hid->io_started) { + dev_warn(&hid->dev, "io already started"); + return; + } + hid->io_started = true; + up(&hid->driver_input_lock); +} + +/** + * hid_device_io_stop - disable HID input during probe, remove + * + * @hid - the device + * + * Should only be called after hid_device_io_start. It will prevent + * incoming packets from going to the driver for the duration of + * probe, remove. If called during probe, packets will still go to the + * driver after probe is complete. This function should only be called + * by the thread calling probe or remove. + */ +static inline void hid_device_io_stop(struct hid_device *hid) { + if (!hid->io_started) { + dev_warn(&hid->dev, "io already stopped"); + return; + } + hid->io_started = false; + down(&hid->driver_input_lock); +} + +/** * hid_map_usage - map usage input bits * * @hidinput: hidinput which we are interested in