On Thu, Mar 5, 2015 at 8:54 PM, Ping Cheng <pinglinux@xxxxxxxxx> wrote:
> On Thu, Mar 5, 2015 at 2:36 PM, Benjamin Tissoires
> <benjamin.tissoires@xxxxxxxxxx> wrote:
>> 486b908 (HID: wacom: do not send pen events before touch is up/forced out)
>> introduces a kernel oops when plugging a tablet without touch.
>
> Thank you for the catch. You must have tried an Intuos 4 or earlier
> model. WACOM_QUIRK_MULTI_INPUT is only set for I5 and later.
>
>> wacom->shared is null for these devices so this leads to a null pointer
>> exception.
>
> The root cause is "if (wacom->shared->touch_down)" was added outside
> of "if (features->quirks & WACOM_QUIRK_MULTI_INPUT)". A consistent fix
> would be:
> ----
> @@ -555,8 +555,11 @@ static int wacom_intuos_inout(struct wacom_wac *wacom)
> (features->type == CINTIQ && !(data[1] & 0x40)))
> return 1;
>
> - if (features->quirks & WACOM_QUIRK_MULTI_INPUT)
> + if (features->quirks & WACOM_QUIRK_MULTI_INPUT) {
> wacom->shared->stylus_in_proximity = true;
> + if (wacom->shared->touch_down)
> + return 1;
> + }
Yes, no, maybe :)
that was my first approach. But then I switched to "if
(wacom->shared)" to actually remember the hackers that wacom->shared
is not always valid and that we should not assume it is.
I don't have any preference except that this needs to be fixed in 4.0 final.
Jiri, do you prefer that I resend the patch? or do you amend it? or do
you keep my first version?
Cheers,
Benjamin
>
> /* in Range while exiting */
> if (((data[1] & 0xfe) == 0x20) && wacom->reporting_data) {
> ----
>
> Cheers,
>
> Ping
>
>> Change the condition to make it clear that what we need is wacom->shared
>> not NULL.
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
>> ---
>>
>> Hi Jiri,
>>
>> this one should be pulled in 4.0. Or we will have surprised users :)
>>
>> Cheers,
>> Benjamin
>>
>> drivers/hid/wacom_wac.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
>> index ff9a7ab..9739a4c 100644
>> --- a/drivers/hid/wacom_wac.c
>> +++ b/drivers/hid/wacom_wac.c
>> @@ -564,11 +564,12 @@ static int wacom_intuos_inout(struct wacom_wac *wacom)
>> (features->type == CINTIQ && !(data[1] & 0x40)))
>> return 1;
>>
>> - if (features->quirks & WACOM_QUIRK_MULTI_INPUT)
>> + if (wacom->shared) {
>> wacom->shared->stylus_in_proximity = true;
>>
>> - if (wacom->shared->touch_down)
>> - return 1;
>> + if (wacom->shared->touch_down)
>> + return 1;
>> + }
>>
>> /* in Range while exiting */
>> if (((data[1] & 0xfe) == 0x20) && wacom->reporting_data) {
>> --
>> 2.1.0
>>
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