From: Jason Gerecke killertofu@gmail.com

If a input device is opened before hid_hw_start is called, events may not be received from the hardware. In the case of USB-backed devices, for example, the hid_hw_start function is responsible for filling in the URB which is submitted when the input device is opened. If a device is opened prematurely, polling will never start because the device will not have been in the correct state to send the URB.

Because the wacom driver registers its input devices before calling hid_hw_start, there is a window of time where a device can be opened and end up in an inoperable state. Some ARM-based Chromebooks in particular reliably trigger this bug.

This commit splits the wacom_register_inputs function into two pieces. One which is responsible for setting up the allocated inputs (and runs prior to hid_hw_start so that devices are ready for any input events they may end up receiving) and another which only registers the devices (and runs after hid_hw_start to ensure devices can be immediately opened without issue). Note that the functions to initialize the LEDs and remotes are also moved after hid_hw_start to maintain their own dependency chains.

Fixes: 7704ac937345 ("HID: wacom: implement generic HID handling for pen generic devices") Cc: stable@vger.kernel.org # v3.18+ Suggested-by: Dmitry Torokhov dmitry.torokhov@gmail.com Signed-off-by: Jason Gerecke jason.gerecke@wacom.com --- drivers/hid/wacom_sys.c | 63 ++++++++++++++++++++++++++++------------- 1 file changed, 43 insertions(+), 20 deletions(-)

diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c index b613f11ed9498..2bc45b24075c3 100644 --- a/drivers/hid/wacom_sys.c +++ b/drivers/hid/wacom_sys.c @@ -2087,7 +2087,7 @@ static int wacom_allocate_inputs(struct wacom *wacom) return 0; }

-static int wacom_register_inputs(struct wacom *wacom) +static int wacom_setup_inputs(struct wacom *wacom) { struct input_dev *pen_input_dev, *touch_input_dev, *pad_input_dev; struct wacom_wac *wacom_wac = &(wacom->wacom_wac); @@ -2106,10 +2106,6 @@ static int wacom_register_inputs(struct wacom *wacom) input_free_device(pen_input_dev); wacom_wac->pen_input = NULL; pen_input_dev = NULL; - } else { - error = input_register_device(pen_input_dev); - if (error) - goto fail; }

error = wacom_setup_touch_input_capabilities(touch_input_dev, wacom_wac); @@ -2118,10 +2114,6 @@ static int wacom_register_inputs(struct wacom *wacom) input_free_device(touch_input_dev); wacom_wac->touch_input = NULL; touch_input_dev = NULL; - } else { - error = input_register_device(touch_input_dev); - if (error) - goto fail; }

error = wacom_setup_pad_input_capabilities(pad_input_dev, wacom_wac); @@ -2130,7 +2122,34 @@ static int wacom_register_inputs(struct wacom *wacom) input_free_device(pad_input_dev); wacom_wac->pad_input = NULL; pad_input_dev = NULL; - } else { + } + + return 0; +} + +static int wacom_register_inputs(struct wacom *wacom) +{ + struct input_dev *pen_input_dev, *touch_input_dev, *pad_input_dev; + struct wacom_wac *wacom_wac = &(wacom->wacom_wac); + int error = 0; + + pen_input_dev = wacom_wac->pen_input; + touch_input_dev = wacom_wac->touch_input; + pad_input_dev = wacom_wac->pad_input; + + if (pen_input_dev) { + error = input_register_device(pen_input_dev); + if (error) + goto fail; + } + + if (touch_input_dev) { + error = input_register_device(touch_input_dev); + if (error) + goto fail; + } + + if (pad_input_dev) { error = input_register_device(pad_input_dev); if (error) goto fail; @@ -2383,6 +2402,20 @@ static int wacom_parse_and_register(struct wacom *wacom, bool wireless) if (error) goto fail;

+ error = wacom_setup_inputs(wacom); + if (error) + goto fail; + + if (features->type == HID_GENERIC) + connect_mask |= HID_CONNECT_DRIVER; + + /* Regular HID work starts now */ + error = hid_hw_start(hdev, connect_mask); + if (error) { + hid_err(hdev, "hw start failed\n"); + goto fail; + } + error = wacom_register_inputs(wacom); if (error) goto fail; @@ -2397,16 +2430,6 @@ static int wacom_parse_and_register(struct wacom *wacom, bool wireless) goto fail; }

- if (features->type == HID_GENERIC) - connect_mask |= HID_CONNECT_DRIVER; - - /* Regular HID work starts now */ - error = hid_hw_start(hdev, connect_mask); - if (error) { - hid_err(hdev, "hw start failed\n"); - goto fail; - } - if (!wireless) { /* Note that if query fails it is not a hard failure */ wacom_query_tablet_data(wacom);