HID: Separate struct hid_device's driver_lock into two locks.

Commit Message

Andrew de los Reyes Feb. 14, 2013, 5:07 a.m. UTC

Here's the latest version of the patch. I believe it addresses all
outstanding comments.

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    | 38 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 58 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 +748,36 @@ 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) {
+  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) {
+  hid->io_started = false;
+  down(&hid->driver_input_lock);
+}
+
+/**
  * hid_map_usage - map usage input bits
  *
  * @hidinput: hidinput which we are interested in

Comments

Jiri Kosina Feb. 18, 2013, 1:08 p.m. UTC | #1

On Wed, 13 Feb 2013, Andrew de los Reyes wrote:

> Here's the latest version of the patch. I believe it addresses all
> outstanding comments.
> 
> 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

Hi,

thanks for finally proceeding on this front.

Please provide your Signed-off-by line; without that, the patch can't be 
accepted.

> ---
>  drivers/hid/hid-core.c | 24 +++++++++++++++++++++---
>  include/linux/hid.h    | 38 +++++++++++++++++++++++++++++++++++++-
>  2 files changed, 58 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 4da66b4..714d8b7 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -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:
> diff --git a/include/linux/hid.h b/include/linux/hid.h
> index 3a95da6..27282a1 100644
> --- a/include/linux/hid.h
> +++ b/include/linux/hid.h
> @@ -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;
>  	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 +748,36 @@ 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) {
> +  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) {
> +  hid->io_started = false;
> +  down(&hid->driver_input_lock);
> +}

Is there any particular reason to have hid_device_io_start() and 
hid_device_io_stop() indentation not use tabs?

Also, the functions are currently unused, so I'd rather suggest adding 
them together when individual device driver(s) are converted to using it.

Thanks again,

Andrew de los Reyes Feb. 18, 2013, 5:20 p.m. UTC | #2

From: Andrew de los Reyes <[e-mail]>

This patch series includes the latest version of the patch to separate
the HID driver lock into two. It also includes the first use of the
new API provided by that patch: a change to the Logitech Unifying
Receiver driver to detect attached peripherals during probe(). With
that in, we can also revert a previous workound, which was originally
introduced when probe() stopped being able to communicate with the
device.

Andrew de los Reyes (3):
  HID: Separate struct hid_device's driver_lock into two locks.
  HID: Fix logitech-dj: Allow incoming packets during probe().
  Revert "HID: Fix logitech-dj: missing Unifying device issue"

 drivers/hid/hid-core.c        | 24 +++++++++++++++++++---
 drivers/hid/hid-logitech-dj.c | 48 +++----------------------------------------
 drivers/hid/hid-logitech-dj.h |  1 -
 include/linux/hid.h           | 46 ++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 69 insertions(+), 50 deletions(-)

--
1.8.1.3

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Jiri Kosina Feb. 25, 2013, 1:03 p.m. UTC | #3

On Mon, 18 Feb 2013, Jiri Kosina wrote:

> > Change-Id: I737f6fc15911134b51273acf8d3de92fa5cc0f85
> 
> Hi,
> 
> thanks for finally proceeding on this front.
> 
> Please provide your Signed-off-by line; without that, the patch can't be 
> accepted.

Andrew, please ... ?

David Herrmann Feb. 25, 2013, 1:09 p.m. UTC | #4

Hi Jiri

On Mon, Feb 25, 2013 at 2:03 PM, Jiri Kosina <[e-mail]> wrote:
> On Mon, 18 Feb 2013, Jiri Kosina wrote:
>
>> > Change-Id: I737f6fc15911134b51273acf8d3de92fa5cc0f85
>>
>> Hi,
>>
>> thanks for finally proceeding on this front.
>>
>> Please provide your Signed-off-by line; without that, the patch can't be
>> accepted.
>
> Andrew, please ... ?

I got the new PATCH with the sign-off. Maybe you missed it?

Subject: [PATCH 1/3] HID: Separate struct hid_device's driver_lock
into two locks.
Date:	Mon, 18 Feb 2013 09:20:21 -0800
Message-Id: <[e-mail]>

Cheers
David
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Jiri Kosina Feb. 25, 2013, 1:15 p.m. UTC | #5

On Mon, 25 Feb 2013, David Herrmann wrote:

> >> Please provide your Signed-off-by line; without that, the patch can't be
> >> accepted.
> >
> > Andrew, please ... ?
> 
> I got the new PATCH with the sign-off. Maybe you missed it?
> 
> Subject: [PATCH 1/3] HID: Separate struct hid_device's driver_lock
> into two locks.
> Date:	Mon, 18 Feb 2013 09:20:21 -0800
> Message-Id: <[e-mail]>

Ah, thanks for the pointer, apparently I wasn't CCed, which increases the 
likelyhood of patches getting lost significantly.

I'll take them from linux-input@ and add to my TODO.

Andrew de los Reyes Feb. 25, 2013, 5:16 p.m. UTC | #6

Sorry, I'll make sure to CC you in the future.

If you look at linux-input@, you'll see I updated the patch and also
included a use of this patch.

-andrew

On Mon, Feb 25, 2013 at 5:15 AM, Jiri Kosina <[e-mail]> wrote:
>
> On Mon, 25 Feb 2013, David Herrmann wrote:
>
> > >> Please provide your Signed-off-by line; without that, the patch can't be
> > >> accepted.
> > >
> > > Andrew, please ... ?
> >
> > I got the new PATCH with the sign-off. Maybe you missed it?
> >
> > Subject: [PATCH 1/3] HID: Separate struct hid_device's driver_lock
> > into two locks.
> > Date: Mon, 18 Feb 2013 09:20:21 -0800
> > Message-Id: <[e-mail]>
>
> Ah, thanks for the pointer, apparently I wasn't CCed, which increases the
> likelyhood of patches getting lost significantly.
>
> I'll take them from linux-input@ and add to my TODO.
>
> --
> Jiri Kosina
> SUSE Labs
> --
> To unsubscribe from this list: send the line "unsubscribe linux-input" in
> the body of a message to [e-mail]
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Jiri Kosina March 1, 2013, 1:15 p.m. UTC | #7

On Mon, 18 Feb 2013, Andrew de los Reyes wrote:

> From: Andrew de los Reyes <[e-mail]>
> 
> This patch series includes the latest version of the patch to separate
> the HID driver lock into two. It also includes the first use of the
> new API provided by that patch: a change to the Logitech Unifying
> Receiver driver to detect attached peripherals during probe(). With
> that in, we can also revert a previous workound, which was originally
> introduced when probe() stopped being able to communicate with the
> device.
> 
> Andrew de los Reyes (3):
>   HID: Separate struct hid_device's driver_lock into two locks.
>   HID: Fix logitech-dj: Allow incoming packets during probe().
>   Revert "HID: Fix logitech-dj: missing Unifying device issue"
> 
>  drivers/hid/hid-core.c        | 24 +++++++++++++++++++---
>  drivers/hid/hid-logitech-dj.c | 48 +++----------------------------------------
>  drivers/hid/hid-logitech-dj.h |  1 -
>  include/linux/hid.h           | 46 ++++++++++++++++++++++++++++++++++++++++-
>  4 files changed, 69 insertions(+), 50 deletions(-)

Now queued in my tree. Thanks,

Patch

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 4da66b4..714d8b7 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -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:
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 3a95da6..27282a1 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -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;