On Tue, Nov 3, 2015 at 4:57 PM, Jason Gerecke <killertofu@xxxxxxxxx> wrote:
> When connecting the Cintiq Companion 2 as an external tablet (i.e., using
> it in "hybrid" mode) it has been seen to cause the kernel of the machine
> it is connected to to Oops. The cause has been traced to us attempting to
> switch the tablet's mode prior to actually starting HID device (resulting
> in the eventual dereference of the uninitialized control URB).
>
> Commit 3b164a0 moved the mode switch from occuring post-start to occurring
> pre-start. The change was not seen to cause issues largely due to the fact
> that most devices mode switch with 'hid_hw_raw_request' (which is safe to
> call prior to start) rather than 'hid_hw_request'.
>
> Moving the call back to its original location resolves the issue, but
> causes some touch-only Bamboo tablets (e.g. 056a:00d0) to stop working.
> The affected tablets require us to perform a mode switch on their
> vestigial pen interface prior ignoring with -ENODEV, meaning that the
> code which is responsible for doing the ignoring has to move as well.
We'll need to clean up the code a bit more. But, that's for future.
This patch is good to go.
> Signed-off-by: Jason Gerecke <jason.gerecke@xxxxxxxxx>
Reviewed-by: Ping Cheng <pingc@xxxxxxxxx>
Ping
> ---
> Jiri,
>
> Ping clued me in to the fact that 'wacom_query_tablet_data' hasn't always
> been in this problematic location. The offending commit mentioned in the
> revised commit summary is queued for 4.4, so this only needs to get into
> the next RC rather than be targeted for stable.
>
> Jason
>
> drivers/hid/wacom_sys.c | 36 ++++++++++++++++++------------------
> 1 file changed, 18 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c
> index abb7fdf..e06af5b 100644
> --- a/drivers/hid/wacom_sys.c
> +++ b/drivers/hid/wacom_sys.c
> @@ -1778,24 +1778,6 @@ static int wacom_probe(struct hid_device *hdev,
> features->device_type |= WACOM_DEVICETYPE_PEN;
> }
>
> - /* Note that if query fails it is not a hard failure */
> - wacom_query_tablet_data(hdev, features);
> -
> - /* touch only Bamboo doesn't support pen */
> - if ((features->type == BAMBOO_TOUCH) &&
> - (features->device_type & WACOM_DEVICETYPE_PEN)) {
> - error = -ENODEV;
> - goto fail_shared_data;
> - }
> -
> - /* pen only Bamboo neither support touch nor pad */
> - if ((features->type == BAMBOO_PEN) &&
> - ((features->device_type & WACOM_DEVICETYPE_TOUCH) ||
> - (features->device_type & WACOM_DEVICETYPE_PAD))) {
> - error = -ENODEV;
> - goto fail_shared_data;
> - }
> -
> wacom_calculate_res(features);
>
> wacom_update_name(wacom);
> @@ -1833,6 +1815,24 @@ static int wacom_probe(struct hid_device *hdev,
> goto fail_hw_start;
> }
>
> + /* Note that if query fails it is not a hard failure */
> + wacom_query_tablet_data(hdev, features);
> +
> + /* touch only Bamboo doesn't support pen */
> + if ((features->type == BAMBOO_TOUCH) &&
> + (features->device_type & WACOM_DEVICETYPE_PEN)) {
> + error = -ENODEV;
> + goto fail_hw_start;
> + }
> +
> + /* pen only Bamboo neither support touch nor pad */
> + if ((features->type == BAMBOO_PEN) &&
> + ((features->device_type & WACOM_DEVICETYPE_TOUCH) ||
> + (features->device_type & WACOM_DEVICETYPE_PAD))) {
> + error = -ENODEV;
> + goto fail_hw_start;
> + }
> +
> if (features->device_type & WACOM_DEVICETYPE_WL_MONITOR)
> error = hid_hw_open(hdev);
>
> --
> 2.6.2
>
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