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* [PATCH] MAINTAINERS: Update rydberg's addresses
@ 2014-12-19  9:06 Henrik Rydberg
  2015-01-19 21:08 ` Benjamin Tissoires
  0 siblings, 1 reply; 12+ messages in thread
From: Henrik Rydberg @ 2014-12-19  9:06 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Dmitry Torokhov, David S. Miller, Greg Kroah-Hartman,
	Joe Perches, Mauro Carvalho Chehab, linux-input, linux-kernel,
	Henrik Rydberg

My ISP finally gave up on the old mail address, so I am moving things
over to bitmath.org instead. Also change the status fields to better
reflect reality.

Signed-off-by: Henrik Rydberg <rydberg@bitmath.org>
---
 MAINTAINERS | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index c721042..62b53e8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -714,15 +714,15 @@ F:	include/uapi/linux/apm_bios.h
 F:	drivers/char/apm-emulation.c
 
 APPLE BCM5974 MULTITOUCH DRIVER
-M:	Henrik Rydberg <rydberg@euromail.se>
+M:	Henrik Rydberg <rydberg@bitmath.org>
 L:	linux-input@vger.kernel.org
-S:	Maintained
+S:	Odd fixes
 F:	drivers/input/mouse/bcm5974.c
 
 APPLE SMC DRIVER
-M:	Henrik Rydberg <rydberg@euromail.se>
+M:	Henrik Rydberg <rydberg@bitmath.org>
 L:	lm-sensors@lm-sensors.org
-S:	Maintained
+S:	Odd fixes
 F:	drivers/hwmon/applesmc.c
 
 APPLETALK NETWORK LAYER
@@ -4813,10 +4813,10 @@ F:	include/uapi/linux/input.h
 F:	include/linux/input/
 
 INPUT MULTITOUCH (MT) PROTOCOL
-M:	Henrik Rydberg <rydberg@euromail.se>
+M:	Henrik Rydberg <rydberg@bitmath.org>
 L:	linux-input@vger.kernel.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/rydberg/input-mt.git
-S:	Maintained
+S:	Odd fixes
 F:	Documentation/input/multi-touch-protocol.txt
 F:	drivers/input/input-mt.c
 K:	\b(ABS|SYN)_MT_
-- 
2.1.3


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2014-12-19  9:06 [PATCH] MAINTAINERS: Update rydberg's addresses Henrik Rydberg
@ 2015-01-19 21:08 ` Benjamin Tissoires
  2015-01-20  0:13   ` Dmitry Torokhov
  2015-01-20 22:26   ` Henrik Rydberg
  0 siblings, 2 replies; 12+ messages in thread
From: Benjamin Tissoires @ 2015-01-19 21:08 UTC (permalink / raw)
  To: Henrik Rydberg
  Cc: Andrew Morton, Dmitry Torokhov, David S. Miller,
	Greg Kroah-Hartman, Joe Perches, Mauro Carvalho Chehab,
	linux-input, linux-kernel

On Fri, Dec 19, 2014 at 4:06 AM, Henrik Rydberg <rydberg@bitmath.org> wrote:
> My ISP finally gave up on the old mail address, so I am moving things
> over to bitmath.org instead. Also change the status fields to better
> reflect reality.
>
> Signed-off-by: Henrik Rydberg <rydberg@bitmath.org>
> ---

Dmitry, it looks like this patch never found its way to your tree...

Henrik, I just used the get_maintainer to add you on CC to an input-mt
patch series, and it ended up using the @euromail.se instead of your
still valid one. I can resend to you the patch series if you want.

Cheers,
Benjamin

>  MAINTAINERS | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c721042..62b53e8 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -714,15 +714,15 @@ F:        include/uapi/linux/apm_bios.h
>  F:     drivers/char/apm-emulation.c
>
>  APPLE BCM5974 MULTITOUCH DRIVER
> -M:     Henrik Rydberg <rydberg@euromail.se>
> +M:     Henrik Rydberg <rydberg@bitmath.org>
>  L:     linux-input@vger.kernel.org
> -S:     Maintained
> +S:     Odd fixes
>  F:     drivers/input/mouse/bcm5974.c
>
>  APPLE SMC DRIVER
> -M:     Henrik Rydberg <rydberg@euromail.se>
> +M:     Henrik Rydberg <rydberg@bitmath.org>
>  L:     lm-sensors@lm-sensors.org
> -S:     Maintained
> +S:     Odd fixes
>  F:     drivers/hwmon/applesmc.c
>
>  APPLETALK NETWORK LAYER
> @@ -4813,10 +4813,10 @@ F:      include/uapi/linux/input.h
>  F:     include/linux/input/
>
>  INPUT MULTITOUCH (MT) PROTOCOL
> -M:     Henrik Rydberg <rydberg@euromail.se>
> +M:     Henrik Rydberg <rydberg@bitmath.org>
>  L:     linux-input@vger.kernel.org
>  T:     git git://git.kernel.org/pub/scm/linux/kernel/git/rydberg/input-mt.git
> -S:     Maintained
> +S:     Odd fixes
>  F:     Documentation/input/multi-touch-protocol.txt
>  F:     drivers/input/input-mt.c
>  K:     \b(ABS|SYN)_MT_
> --
> 2.1.3
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2015-01-19 21:08 ` Benjamin Tissoires
@ 2015-01-20  0:13   ` Dmitry Torokhov
  2015-01-20  0:34     ` Benjamin Tissoires
  2015-01-20 22:26   ` Henrik Rydberg
  1 sibling, 1 reply; 12+ messages in thread
From: Dmitry Torokhov @ 2015-01-20  0:13 UTC (permalink / raw)
  To: Benjamin Tissoires
  Cc: Henrik Rydberg, Andrew Morton, David S. Miller,
	Greg Kroah-Hartman, Joe Perches, Mauro Carvalho Chehab,
	linux-input, linux-kernel

On Mon, Jan 19, 2015 at 04:08:19PM -0500, Benjamin Tissoires wrote:
> On Fri, Dec 19, 2014 at 4:06 AM, Henrik Rydberg <rydberg@bitmath.org> wrote:
> > My ISP finally gave up on the old mail address, so I am moving things
> > over to bitmath.org instead. Also change the status fields to better
> > reflect reality.
> >
> > Signed-off-by: Henrik Rydberg <rydberg@bitmath.org>
> > ---
> 
> Dmitry, it looks like this patch never found its way to your tree...

It went through akpm and is in mainline now.

Thanks.

-- 
Dmitry

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2015-01-20  0:13   ` Dmitry Torokhov
@ 2015-01-20  0:34     ` Benjamin Tissoires
  0 siblings, 0 replies; 12+ messages in thread
From: Benjamin Tissoires @ 2015-01-20  0:34 UTC (permalink / raw)
  To: Dmitry Torokhov
  Cc: Henrik Rydberg, Andrew Morton, David S. Miller,
	Greg Kroah-Hartman, Joe Perches, Mauro Carvalho Chehab,
	linux-input, linux-kernel

On Mon, Jan 19, 2015 at 7:13 PM, Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
> On Mon, Jan 19, 2015 at 04:08:19PM -0500, Benjamin Tissoires wrote:
>> On Fri, Dec 19, 2014 at 4:06 AM, Henrik Rydberg <rydberg@bitmath.org> wrote:
>> > My ISP finally gave up on the old mail address, so I am moving things
>> > over to bitmath.org instead. Also change the status fields to better
>> > reflect reality.
>> >
>> > Signed-off-by: Henrik Rydberg <rydberg@bitmath.org>
>> > ---
>>
>> Dmitry, it looks like this patch never found its way to your tree...
>
> It went through akpm and is in mainline now.
>

OK, then sorry for the noise, I should have updated my tree to master
before sending this :(

Cheers,
Benjamin

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2015-01-19 21:08 ` Benjamin Tissoires
  2015-01-20  0:13   ` Dmitry Torokhov
@ 2015-01-20 22:26   ` Henrik Rydberg
  2015-01-21  4:35     ` Peter Hutterer
  1 sibling, 1 reply; 12+ messages in thread
From: Henrik Rydberg @ 2015-01-20 22:26 UTC (permalink / raw)
  To: Benjamin Tissoires
  Cc: Andrew Morton, Dmitry Torokhov, David S. Miller,
	Greg Kroah-Hartman, Joe Perches, Mauro Carvalho Chehab,
	linux-input, linux-kernel

Hi Benjamin,

> Henrik, I just used the get_maintainer to add you on CC to an input-mt
> patch series, and it ended up using the @euromail.se instead of your
> still valid one. I can resend to you the patch series if you want.

Thanks, that won't be necessary.

I looked through the the patchset, and it strikes me as mostly renames without
deeper explanations, which all in all puts them in the not-needed category, I am
afraid. An in-depth explanation could be added as a text block somewhere without
touching the current code.

The only patch that does something is the last one, and what it does could
easily be performed in userland, by further processing of the contacts there. I
therefore see no use for any of those patches in the kernel.

Is there a good reason for the first reaction to be to add special tweaks such
as this one in the kernel, rather than in a dedicated userland input system? I
am genuinely curious.

Thanks,
Henrik


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2015-01-20 22:26   ` Henrik Rydberg
@ 2015-01-21  4:35     ` Peter Hutterer
  2015-01-21 15:25       ` Henrik Rydberg
  0 siblings, 1 reply; 12+ messages in thread
From: Peter Hutterer @ 2015-01-21  4:35 UTC (permalink / raw)
  To: Henrik Rydberg
  Cc: Benjamin Tissoires, Andrew Morton, Dmitry Torokhov,
	David S. Miller, Greg Kroah-Hartman, Joe Perches,
	Mauro Carvalho Chehab, linux-input, linux-kernel

On Tue, Jan 20, 2015 at 11:26:20PM +0100, Henrik Rydberg wrote:
> Hi Benjamin,
> 
> > Henrik, I just used the get_maintainer to add you on CC to an input-mt
> > patch series, and it ended up using the @euromail.se instead of your
> > still valid one. I can resend to you the patch series if you want.
> 
> Thanks, that won't be necessary.
> 
> I looked through the the patchset, and it strikes me as mostly renames without
> deeper explanations, which all in all puts them in the not-needed category, I am
> afraid. An in-depth explanation could be added as a text block somewhere without
> touching the current code.

I disagree. Patches that improve readability of the code are rarely in the
not-needed category. Looking at Input: mt: document input_mt_set_matrix()
for example: without that comment I'd have no idea if what the function does
is correct or not because I'd have no idea what it's _supposed_ to do.
 
> The only patch that does something is the last one, and what it does could
> easily be performed in userland, by further processing of the contacts there. I
> therefore see no use for any of those patches in the kernel.
> 
> Is there a good reason for the first reaction to be to add special tweaks such
> as this one in the kernel, rather than in a dedicated userland input system? I
> am genuinely curious.

it wasn't the first reaction. it was the third, after we hacked up 
synaptics [1], then libinput [2], both rather unsatisfactory. Not sure what
chromeos does but they'll probably would need similar code. And any other
users of the evdev API of course.

Anyway, yes, you're right, it can be done in userland, depending on the
implementation of userland. Putting proper support for this in synaptics
would require a rather large rewrite of the touch handling for example [3]
So we need multiple different implementations. Of course, we could factor
this out into a library, at which point we have another API to track and
piece of code to maintain and slot in between the device node and the
consumer of the events. And effectively we'd have then written the same code
that's already in the kernel anyway (which we can't copy directly because
GPL vs MIT etc.).

The big ticket item though is that without this patch the message is: you
can't trust protocol B to actually track the touchpoints correctly. Which
goes against to what it's supposed to help with in the first place.
So now we need some userspace code to verify the kernel touchpoint tracking,
but since this only affects some devices you'd need some code to identify
devices that need to be double checked. The kernel has that info, we don't
have (all of) it in userspace. All of this effort to work around what the
kernel is supposed to do in the first place.

So yeah, I think there are plenty of good reasons for having this in the
kernel :)

Cheers,
   Peter

[1] http://lists.x.org/archives/xorg-devel/2014-September/043866.html
[2] http://lists.freedesktop.org/archives/wayland-devel/2014-September/017340.html
[3] which I try to avoid given that synaptics is somewhere between hanging
on life support and receiving pallative care.

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2015-01-21  4:35     ` Peter Hutterer
@ 2015-01-21 15:25       ` Henrik Rydberg
  2015-01-21 16:23         ` Benjamin Tissoires
  0 siblings, 1 reply; 12+ messages in thread
From: Henrik Rydberg @ 2015-01-21 15:25 UTC (permalink / raw)
  To: Peter Hutterer
  Cc: Benjamin Tissoires, Andrew Morton, Dmitry Torokhov,
	David S. Miller, Greg Kroah-Hartman, Joe Perches,
	Mauro Carvalho Chehab, linux-input, linux-kernel

Hi Peter,

> it wasn't the first reaction. it was the third, after we hacked up
> synaptics [1], then libinput [2], both rather unsatisfactory. Not sure what
> chromeos does but they'll probably would need similar code. And any other
> users of the evdev API of course.

So if this approach did not work very well in userland, why would it work any
better in the kernel?

Henrik


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2015-01-21 15:25       ` Henrik Rydberg
@ 2015-01-21 16:23         ` Benjamin Tissoires
  2015-01-21 19:38           ` Henrik Rydberg
  0 siblings, 1 reply; 12+ messages in thread
From: Benjamin Tissoires @ 2015-01-21 16:23 UTC (permalink / raw)
  To: Henrik Rydberg
  Cc: Peter Hutterer, Andrew Morton, Dmitry Torokhov, David S. Miller,
	Greg Kroah-Hartman, Joe Perches, Mauro Carvalho Chehab,
	linux-input, linux-kernel

On Wed, Jan 21, 2015 at 10:25 AM, Henrik Rydberg <rydberg@bitmath.org> wrote:
> Hi Peter,
>
>> it wasn't the first reaction. it was the third, after we hacked up
>> synaptics [1], then libinput [2], both rather unsatisfactory. Not sure what
>> chromeos does but they'll probably would need similar code. And any other
>> users of the evdev API of course.
>
> So if this approach did not work very well in userland, why would it work any
> better in the kernel?
>

I would have thought that Peter's answer was clear enough:
- there is a fragmentation problem: we would have to fix the bug in
xorg-synaptics (which is slowly waiting for its death), libinput,
ChromeOS, Qt Embedded, Kivy (I think), etc... We can do it, to some
extend, but we will have to explain the following to our users:
- it means that the mt protocol B can not be relied upon, because even
if we state that each touch has its own slot, then it is false in this
case. This was Peter last point.

Also, if you compare the libinput implementation of the handling of
the cursors jumps and the kernel implementation I proposed, there is a
big difference in term of simplicity.

In the kernel, while we are assigning the tracking IDs, we detect that
there is a jump, and we "just" have to generate a new slot and close
the first (done by 1 assignment of -1 to the current tracking ID).

In Libinput, well, you receive a slot, there is a jump, you detect it,
then you have to create a new fake kernel event to stop the current
slot, create a new one, and you then have to rewind the current state
of the buttons, the hysteresis, add special case handling and
hopefully, you did not introduced a bug in all the complex code. So
you need to write unit tests (not an argument, I concede, but this is
extra work), and in the future, someone will not understand what this
is all about because the kernel should guarantee that the slots are
sane.

If I were grumpy (and I can be, ask Peter), I would say that sure, we
can add such a case in the mtdev library, but the point of having the
in-kernel tracking system was to slowly get away from the head over
added by mtdev.

Cheers,
Benjamin

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2015-01-21 16:23         ` Benjamin Tissoires
@ 2015-01-21 19:38           ` Henrik Rydberg
  2015-01-22  4:21             ` Fixing touch point jumps in the kernel (was Re: [PATCH] MAINTAINERS: Update rydberg's addresses) Peter Hutterer
  2015-02-15 12:19             ` [PATCH] MAINTAINERS: Update rydberg's addresses Pavel Machek
  0 siblings, 2 replies; 12+ messages in thread
From: Henrik Rydberg @ 2015-01-21 19:38 UTC (permalink / raw)
  To: Benjamin Tissoires
  Cc: Peter Hutterer, Andrew Morton, Dmitry Torokhov, David S. Miller,
	Greg Kroah-Hartman, Joe Perches, Mauro Carvalho Chehab,
	linux-input, linux-kernel

Hi Benjamin,

> - there is a fragmentation problem: we would have to fix the bug in
> xorg-synaptics (which is slowly waiting for its death), libinput,
> ChromeOS, Qt Embedded, Kivy (I think), etc...

Indeed, this is the problem I wanted to highlight. As the fragmentation problem
grows (graphics, input, compositors, toolkits), the need for a common
denominator grows as well. However, I do not think the kernel should be the
single common denominator for all the world's problems. Rather, the purpose of
the kernel is to convey hardware information and control as accurately,
effectively and generically as possible.

> - it means that the mt protocol B can not be relied upon, because even
> if we state that each touch has its own slot, then it is false in this
> case.

The case we are talking about is due to information missing in the hardware. At
low enough sampling frequencies, there is no way to distinguish between a moving
finger and a lift-and-press action. We could flag this hardware deficiency
somehow, but making shit up in order to maintain the statue that we do have
enough information is just asking for trouble.

I agree that this point is valid: we cannot always trust the interpretation of
touchpoints for certain hardware. However, there is nothing we can do about
that, except flag for it.

> Also, if you compare the libinput implementation of the handling of
> the cursors jumps and the kernel implementation I proposed, there is a
> big difference in term of simplicity.

No, this is wrong.

> In the kernel, while we are assigning the tracking IDs, we detect that
> there is a jump, and we "just" have to generate a new slot and close
> the first (done by 1 assignment of -1 to the current tracking ID).

The kernel case would have to be accompanied by parameters, under the control of
some user process, where adjustments are made to accomodate different usecases
such as painting, gaming, air guitar playing, flick gestures, multi-user
tablets, etc, etc. That is complex and unwanted.

> In Libinput, well, you receive a slot, there is a jump, you detect it,
> then you have to create a new fake kernel event to stop the current
> slot, create a new one, and you then have to rewind the current state
> of the buttons, the hysteresis, add special case handling and
> hopefully, you did not introduced a bug in all the complex code. So
> you need to write unit tests (not an argument, I concede, but this is
> extra work), and in the future, someone will not understand what this
> is all about because the kernel should guarantee that the slots are
> sane.

You do not need to do any of this (except the test cases, which would be needed
anyway given the context-dependent interpretation of scarse data) if you
intercept the touch points as they come in from the kernel, before the contact
dynamics is fully trusted. Last time I checked that was mtdev or the touch frame
layer or Xinput.

> If I were grumpy (and I can be, ask Peter), I would say that sure, we
> can add such a case in the mtdev library, but the point of having the
> in-kernel tracking system was to slowly get away from the head over
> added by mtdev.

No, this was not the reason. The tree main reasons were actually latency and
power and code reduction. The mtdev layer still provides the functional bridge
needed. However, the latency and number of cpu cycles involved in transferring
the data to userland before throwing most of it away were much reduced by adding
the in-kernel tracking. Collecting the diversity of solutions for older hardware
was a maintainability bonus.

Regarding the practical problem at hand, that double taps sometimes get
misinterpreted as a "flash move", perhaps the problem really is in how we define
a double tap.

When I was writing a certain gesture engine, I realized I got issues with
multi-finger taps. In my case the problem was not due to misinterpreted finger
data, but simply because pressing four fingers simultaneously is not easy, and
really not needed in order to define the gesture per se. So in order to
correctly interpret gestures, I had to involve time in various ways; checking
for overlaps between fingers over a short time span, looking for the maximum
number of fingers within a certain timespan, etc. Not to mention palm detection;
in this context, the individual touch points really lose some meaning.

The double tap is no different in this regard. Nor is a flash move. But we would
not want a real flash move to be interpreted as double tap, would we?

My point is that the gesture context is where the ultimate decision can best be
made - where there is enough information to best approximate what the imperfect
hardware is trying to tell us. If the time between touch down and a fast
movement to a nearby point is consistent with a tap, then maybe it is a tap.

End rant. I hope it helps one way or the other.

Thanks,
Henrik


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Fixing touch point jumps in the kernel (was Re: [PATCH] MAINTAINERS: Update rydberg's addresses)
  2015-01-21 19:38           ` Henrik Rydberg
@ 2015-01-22  4:21             ` Peter Hutterer
  2015-01-22  8:00               ` Henrik Rydberg
  2015-02-15 12:19             ` [PATCH] MAINTAINERS: Update rydberg's addresses Pavel Machek
  1 sibling, 1 reply; 12+ messages in thread
From: Peter Hutterer @ 2015-01-22  4:21 UTC (permalink / raw)
  To: Henrik Rydberg
  Cc: Benjamin Tissoires, Andrew Morton, Dmitry Torokhov,
	David S. Miller, Greg Kroah-Hartman, Joe Perches,
	Mauro Carvalho Chehab, linux-input, linux-kernel

changed the subject so it'll be easier to find in the archives.

On Wed, Jan 21, 2015 at 08:38:46PM +0100, Henrik Rydberg wrote:
> Hi Benjamin,
> 
> > - there is a fragmentation problem: we would have to fix the bug in
> > xorg-synaptics (which is slowly waiting for its death), libinput,
> > ChromeOS, Qt Embedded, Kivy (I think), etc...
> 
> Indeed, this is the problem I wanted to highlight. As the fragmentation problem
> grows (graphics, input, compositors, toolkits), the need for a common
> denominator grows as well. However, I do not think the kernel should be the
> single common denominator for all the world's problems. Rather, the purpose of
> the kernel is to convey hardware information and control as accurately,
> effectively and generically as possible.
> 
> > - it means that the mt protocol B can not be relied upon, because even
> > if we state that each touch has its own slot, then it is false in this
> > case.
> 
> The case we are talking about is due to information missing in the hardware. At
> low enough sampling frequencies, there is no way to distinguish between a moving
> finger and a lift-and-press action. We could flag this hardware deficiency
> somehow, but making shit up in order to maintain the statue that we do have
> enough information is just asking for trouble.
> 
> I agree that this point is valid: we cannot always trust the interpretation of
> touchpoints for certain hardware. However, there is nothing we can do about
> that, except flag for it.
> 
> > Also, if you compare the libinput implementation of the handling of
> > the cursors jumps and the kernel implementation I proposed, there is a
> > big difference in term of simplicity.
> 
> No, this is wrong.
>
> > In the kernel, while we are assigning the tracking IDs, we detect that
> > there is a jump, and we "just" have to generate a new slot and close
> > the first (done by 1 assignment of -1 to the current tracking ID).
> 
> The kernel case would have to be accompanied by parameters, under the control of
> some user process, where adjustments are made to accomodate different usecases
> such as painting, gaming, air guitar playing, flick gestures, multi-user
> tablets, etc, etc. That is complex and unwanted.

from the testing I've done, you cannot trigger this except by lifting a
finger and raising a finger. There is no per-use-case requirement, it's a
hardware deficiency that the hardware simply cannot detect this specific
case of finger change.

Also, note that the patch series has an explicit "In order not to penalize
better sensors, this parameter is not automatically enabled, but each driver
has to manually set it to a reasonable value." so far we have only seen this
on synaptics touchpads which has its own driver. so this wouldn't affect any
device that doesn't need this anyway.

so yes, we could implement a better gesture recognition like you explain
below but it's also unneded on all but a few devices - which, in userspace,
we cannot identify easily.
 
> > In Libinput, well, you receive a slot, there is a jump, you detect it,
> > then you have to create a new fake kernel event to stop the current
> > slot, create a new one, and you then have to rewind the current state
> > of the buttons, the hysteresis, add special case handling and
> > hopefully, you did not introduced a bug in all the complex code. So
> > you need to write unit tests (not an argument, I concede, but this is
> > extra work), and in the future, someone will not understand what this
> > is all about because the kernel should guarantee that the slots are
> > sane.
> 
> You do not need to do any of this (except the test cases, which would be needed
> anyway given the context-dependent interpretation of scarse data) if you
> intercept the touch points as they come in from the kernel, before the contact
> dynamics is fully trusted. Last time I checked that was mtdev or the touch frame
> layer or Xinput.

mtdev is only used for protocol A devices these days so it doesn't apply on
the synaptics pads.

I was thinking of adding this to libevdev so at least _I_ only have to
implement this once. except that for every touchpoint that I fix up in
libevdev I then also have to maintain a correct tracking_id mapping since
now the kernel and the userspace tracking IDs are out of sync.

that leaves synaptics which for historical reasons can handle a device state
but is bad at transitions. Injecting events requires a rewrite of much of
the code. evdev - not as bad but similar. Since this only affects synaptics
pads so far at least we don't have to worry about other drivers (in xorg at
least).

> > If I were grumpy (and I can be, ask Peter), I would say that sure, we
> > can add such a case in the mtdev library, but the point of having the
> > in-kernel tracking system was to slowly get away from the head over
> > added by mtdev.
> 
> No, this was not the reason. The tree main reasons were actually latency and
> power and code reduction. The mtdev layer still provides the functional bridge
> needed. However, the latency and number of cpu cycles involved in transferring
> the data to userland before throwing most of it away were much reduced by adding
> the in-kernel tracking. Collecting the diversity of solutions for older hardware
> was a maintainability bonus.
> 
> Regarding the practical problem at hand, that double taps sometimes get
> misinterpreted as a "flash move", perhaps the problem really is in how we define
> a double tap.
> 
> When I was writing a certain gesture engine, I realized I got issues with
> multi-finger taps. In my case the problem was not due to misinterpreted finger
> data, but simply because pressing four fingers simultaneously is not easy, and
> really not needed in order to define the gesture per se. So in order to
> correctly interpret gestures, I had to involve time in various ways; checking
> for overlaps between fingers over a short time span, looking for the maximum
> number of fingers within a certain timespan, etc. Not to mention palm detection;
> in this context, the individual touch points really lose some meaning.
> 
> The double tap is no different in this regard. Nor is a flash move. But we would
> not want a real flash move to be interpreted as double tap, would we?
> 
> My point is that the gesture context is where the ultimate decision can best be
> made - where there is enough information to best approximate what the imperfect
> hardware is trying to tell us. If the time between touch down and a fast
> movement to a nearby point is consistent with a tap, then maybe it is a tap.

again, you cannot trigger this by moving. or at least if you do your
pointer would be in the bottom right corner anyway because you have to move
the finger so insanely fast that pointer control is clearly not in the
picture anymore. but you can trigger it 1 out of 3 times by lifting your
finger from the touchpad while trying to click a button with your thumb.
right now this means that those touchpads are virtually unsuable (this is a
common interaction method).

and, again: this is a solution for one specific set of devices.

Cheers,
   Peter

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: Fixing touch point jumps in the kernel (was Re: [PATCH] MAINTAINERS: Update rydberg's addresses)
  2015-01-22  4:21             ` Fixing touch point jumps in the kernel (was Re: [PATCH] MAINTAINERS: Update rydberg's addresses) Peter Hutterer
@ 2015-01-22  8:00               ` Henrik Rydberg
  0 siblings, 0 replies; 12+ messages in thread
From: Henrik Rydberg @ 2015-01-22  8:00 UTC (permalink / raw)
  To: Peter Hutterer
  Cc: Benjamin Tissoires, Andrew Morton, Dmitry Torokhov,
	David S. Miller, Greg Kroah-Hartman, Joe Perches,
	Mauro Carvalho Chehab, linux-input, linux-kernel

Hi Peter,

> from the testing I've done, you cannot trigger this except by lifting a
> finger and raising a finger. There is no per-use-case requirement, it's a
> hardware deficiency that the hardware simply cannot detect this specific
> case of finger change.

This is a good selling point, but...

> again, you cannot trigger this by moving. or at least if you do your
> pointer would be in the bottom right corner anyway because you have to move
> the finger so insanely fast that pointer control is clearly not in the
> picture anymore.

this is what puts me off again. It takes me back to the old arcade days, and
watching kids hammer at the controls. What is insane for one person may not be
insane for another.

That said, I understand and agree that there exists an upper move velocity that
makes sense for any particular touchpad.

So I will accept two patches on this: one to set the speed limit in the MT
layer, and one which uses that limit to solve a real problem, for the touchpad
in question.

Let's end this thread here and leave unrelated people in peace.

Thanks,
Henrik


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] MAINTAINERS: Update rydberg's addresses
  2015-01-21 19:38           ` Henrik Rydberg
  2015-01-22  4:21             ` Fixing touch point jumps in the kernel (was Re: [PATCH] MAINTAINERS: Update rydberg's addresses) Peter Hutterer
@ 2015-02-15 12:19             ` Pavel Machek
  1 sibling, 0 replies; 12+ messages in thread
From: Pavel Machek @ 2015-02-15 12:19 UTC (permalink / raw)
  To: Henrik Rydberg
  Cc: Benjamin Tissoires, Peter Hutterer, Andrew Morton,
	Dmitry Torokhov, David S. Miller, Greg Kroah-Hartman,
	Joe Perches, Mauro Carvalho Chehab, linux-input, linux-kernel

On Wed 2015-01-21 20:38:46, Henrik Rydberg wrote:
> Hi Benjamin,
> 
> > - there is a fragmentation problem: we would have to fix the bug in
> > xorg-synaptics (which is slowly waiting for its death), libinput,
> > ChromeOS, Qt Embedded, Kivy (I think), etc...
> 
> Indeed, this is the problem I wanted to highlight. As the fragmentation problem
> grows (graphics, input, compositors, toolkits), the need for a common
> denominator grows as well. However, I do not think the kernel should be the
> single common denominator for all the world's problems. Rather, the purpose of
> the kernel is to convey hardware information and control as accurately,
> effectively and generically as possible.

No, sorry, that's not true.

Kernel should provide hardware abstraction, hiding differences between
different machines.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

^ permalink raw reply	[flat|nested] 12+ messages in thread

end of thread, other threads:[~2015-02-15 12:19 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-12-19  9:06 [PATCH] MAINTAINERS: Update rydberg's addresses Henrik Rydberg
2015-01-19 21:08 ` Benjamin Tissoires
2015-01-20  0:13   ` Dmitry Torokhov
2015-01-20  0:34     ` Benjamin Tissoires
2015-01-20 22:26   ` Henrik Rydberg
2015-01-21  4:35     ` Peter Hutterer
2015-01-21 15:25       ` Henrik Rydberg
2015-01-21 16:23         ` Benjamin Tissoires
2015-01-21 19:38           ` Henrik Rydberg
2015-01-22  4:21             ` Fixing touch point jumps in the kernel (was Re: [PATCH] MAINTAINERS: Update rydberg's addresses) Peter Hutterer
2015-01-22  8:00               ` Henrik Rydberg
2015-02-15 12:19             ` [PATCH] MAINTAINERS: Update rydberg's addresses Pavel Machek

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