On 1/31/2020 8:38 PM, Dmitry Torokhov wrote:
On Fri, Jan 31, 2020 at 10:28:23AM -0800, Andrew Duggan wrote:
On 1/28/20 9:22 AM, Christopher Heiny wrote:
On Tue, 2020-01-28 at 10:41 +0100, Lucas Stach wrote:
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Hi Christopher,
On Di, 2020-01-28 at 07:02 +0000, Christopher Heiny wrote:
On Mon, 2020-01-27 at 11:21 -0800, Andrew Duggan wrote:
Hi Dmitry,
On 1/26/20 6:24 PM, Dmitry Torokhov wrote:
On Mon, Jan 20, 2020 at 12:16:28PM +0100, Lucas Stach wrote:
When the distance thresholds are set the controller must be
in
reduced
reporting mode for them to have any effect on the interrupt
generation.
This has a potentially large impact on the number of events
the
host
needs to process.
Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
---
I'm not sure if we want a separate DT property to allow the
use
of
reduced reporting mode, as this change might lead to problems
for
controllers with unreasonably large threshold values. I'm not
sure if
any controller with bogus threshold values exist in the wild.
---
Andrew, any feedback on this patch?
Thanks!
The RMI4 spec does say that delta X/Y thresholds are only used in
reduced reporting mode, so this patch is needed for the threshold
values
to have an effect.
Reviewed-by: Andrew Duggan <aduggan@xxxxxxxxxxxxx>
Because reduced reporting mode is so dependent on these
thresholds,
my
opinion is that it is better not to add a separate DT property,
but
to
instead control reduced reporting mode through the setting of
these
thresholds. My guess is that the if reduced reporting is not
enabled
in
the firmware by default, then the thresholds may not be valid.
Setting
the thresholds to 0 will essentially disable reduced reporting
mode.
So
that would be how a user could disable reduced reporting mode
without
a
separate DT property. Chris, do you have an opinion on this?
Anything
I
overlooked?
Hi Dmitry, Andrew, Lucas,
I'm in agreement with Andrew on this. Having two ways to
enable/disable reduced reporting (that is, both the DT property and
the
thresholds) could lead to confusion and unexpected
behavior. Simpler
is better, in my opinion.
However, in that case I'm a little concerned about the logic in the
patch below. When either of the thresholds are set to non-zero, we
clear the report mask and then enable the reduced reporting bit.
Subsequently setting both thresholds to zero will disable reduced
reporting, but will not enable another report mode. Unless there
is
code elsewhere to catch this case (and if there is, it seems like a
bad
idea to be handling this in two different places), it could result
in
the touchpad being disabled.
As a hypothetical instance of this, imagine a user using the
touchpad
to manipulate report threshold sliders in a GUI. Setting both
sliders
to zero would disable the touch sensor reporting, potentially
leaving
the user with a dead touch sensor and no easy way to recover from
that.
I can see how this would be a problem, but then I see no interface in
the driver to actually change the threshold values on the fly. They
are
either set by firmware or specified via DT properties. So I don't see
how the threshold values would change on an active device. Anything
i'm
overlooking?
Hi Lucas,
You're not overlooking anything. Mainly it's me being a worry-wart,
and assuming that if something can be adjusted, someone will eventually
come along and add a sysfs interface to adjust it, and then someone
else will create a userspace tool to adjust it, and things will break.
If you guys are OK with Andrew's original evaluation, then you can
ignore my worry (which is, as admitted, entirely a hypothetical).
Cheers,
Chris
Currently, the driver only sets the thresholds in rmi_f11_initialize(). If
someone were to decide to add another method for setting the thresholds they
would probably remove the logic from rmi_f11_initialize() and put it in a
new function so that the code can be called from multiple places. In that
case, they should also include the code in this patch in the new function. I
think the comment above the new code makes it clear that setting the
reporting mode to reduced reporting is needed for the threshold values to be
used by the firmware. I don't see a way to handle potential future changes
without adding what may be unnecessary complexity. I reaffirm my review sign
off.
Applied, thank you everyone.
Hi everyone,
I believe there may be an issue with the reduced reporting mode, at
least on my machine. I have a Lenovo ThinkPad X250 with the Synaptics
TM3075-002 trackpad.
With this patch, the trackpad becomes unusable. On a reboot, my control
register values are [38 00 19 19 00 10 90 06 ea 03 0f 01]. This
corresponds to a delta X/Y threshold of 25 and a palm rejection value of
0. The protocol documentation mentions that the palm rejection value
becomes active when in reduced reporting mode, hence its inclusion here.
Sometimes I could get the mouse to move very sporadically if I used my
entire hand on the trackpad. I instrumented the f11_attention IRQ
handler and found that it was not being called except for these sporadic
movements. I tried a few different combinations of these three values,
but they had no effect. This included setting all three values to 0,
which in theory will yield the same behavior as continuous reporting
mode, but it did not on my machine.
This leads me to suspect a hardware/firmware bug.
I believe the idea was that the platform/configuration could set
sensor->axis_align.delta_x(/y)_threshold to 0 in order to disable the
reduced reporting mode. This is the case on my laptop, but only a
nonzero value will override the value from the firmware, so the reduced
reporting mode still gets enabled.
All the best,
Paul
