On Sun, Oct 24, 2010 at 12:40 PM, <ch...@cnpbagwell.com> wrote:
> From: Chris Bagwell <ch...@cnpbagwell.com>
>
> There is an implied agreement between kernel drivers and
> user land to work around event filtering issues. Document
> our current approach since it seems not so obvious the
> importance of a memset().
>
> Our current approach works great with wacom tablets but
> has some issues with non-wacom tablets. List some TODO's
> to aid those developers in the future.
>
> Also, forcing in proximity handles a few corner cases fine for
> all wacom devices but document the preferred approach for
> possible future patch.
>
> Signed-off-by: Chris Bagwell <ch...@cnpbagwell.com>
Reviewed-by: Ping Cheng <pingli...@gmail.com>
Thank you Chris for adding the comments for non-Wacom devices while we
are becoming device neutral these days.
I may be unable to reply to your other two patches before next month.
Ping
> ---
> src/wcmUSB.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 44 insertions(+), 0 deletions(-)
>
> diff --git a/src/wcmUSB.c b/src/wcmUSB.c
> index c8d775f..eed755e 100644
> --- a/src/wcmUSB.c
> +++ b/src/wcmUSB.c
> @@ -1224,11 +1224,55 @@ static void usbDispatchEvents(InputInfoPtr pInfo)
> pChannel = common->wcmChannel + channel;
> dslast = pChannel->valid.state;
>
> + /* Because of linux input filtering, the kernel driver can not
> + * always force total set of event data when new tool comes into
> + * proximity. This includes simple case of flipping stylus
> + * from pen to eraser tool. Therefore, when new tool is in-prox
> + * we must initialize all shared event values to same as previous
> + * tool to account for filtered events.
> + *
> + * For Generic and Protocol 4 devices that have fixed channel
> + * mappings, this is no problem. Protocol 5 devices are difficult
> + * because they dynamically assign channel #'s and even simple
> + * case above can switch from channel 1 to channel 0.
> + *
> + * To simplify things, we take advantage of fact wacom kernel
> + * drivers force all values to zero when going out of proximity so
> + * we take a short cut and memset() to align when going in-prox
> + * instead of a memcpy().
> + *
> + * TODO: Some non-wacom tablets send X/Y data right before coming
> + * in proximity. The following discards that data.
> + * Adding "&& dslast.proximimty" to check would probably help
> + * this case.
> + * Some non-wacom tablets may also never reset their values
> + * to zero when out-of-prox. The memset() can loss this data.
> + * Adding a !WCM_PROTOCOL_GENERIC check would probably help this case.
> + */
> if (!common->wcmChannel[channel].work.proximity)
> {
> memset(&common->wcmChannel[channel],0,sizeof(WacomChannel));
>
> /* in case the in-prox event was missing */
> + /* TODO: There are not valid times when in-prox
> + * events are not sent by a driver except:
> + *
> + * 1) Starting X while tool is already in prox.
> + * 2) Non-wacom tablet sends only BTN_TOUCH without
> + * BTN_TOOL_PEN since it only support 1 tool.
> + *
> + * Case 1) should be handled in same location as
> + * below check of (ds->device_type == 0) since its
> + * same reason. It is better to query for real
> + * value instead of assuming in-prox.
> + * Case 2) should be handled in case statement that
> + * processes BTN_TOUCH for WCM_PROTOCOL_GENERIC devices.
> + *
> + * So we should not be forcing to in-prox here because
> + * it could cause cursor jump from (X,Y)=(0,0) if events
> + * are sent while out-of-prox; which can happen only
> + * with WCM_PROTOCOL_GENERIC devices. Hint: see TODO above.
> + */
> common->wcmChannel[channel].work.proximity = 1;
> }
>
> --
> 1.7.3.1
>
>
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Nokia and AT&T present the 2010 Calling All Innovators-North America contest
Create new apps & games for the Nokia N8 for consumers in U.S. and Canada
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Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store
http://p.sf.net/sfu/nokia-dev2dev
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