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SubjectRe: [PATCH] media: rc: double keypresses due to timeout expiring to early
On Fri, Nov 17, 2017 at 03:52:50PM +0100, Matthias Reichl wrote:
> Hi Sean!
>
> On Thu, Nov 16, 2017 at 09:54:51PM +0000, Sean Young wrote:
> > Since commit d57ea877af38 ("media: rc: per-protocol repeat period"),
> > double keypresses are reported on the ite-cir driver. This is due
> > two factors: that commit reduced the timeout used for some protocols
> > (it became protocol dependant) and the high default IR timeout used
> > by the ite-cir driver.
> >
> > Some of the IR decoders wait for a trailing space, as that is
> > the only way to know if the bit stream has ended (e.g. rc-6 can be
> > 16, 20 or 32 bits). The longer the IR timeout, the longer it will take
> > to receive the trailing space, delaying decoding and pushing it past the
> > keyup timeout.
> >
> > So, add the IR timeout to the keyup timeout.
>
> Thanks a lot for the patch, I've asked the people with ite-cir
> receivers to test it.
>
> In the meanwhile I ran some tests with gpio-ir-recv and timeout
> set to 200ms with a rc-5 remote (that's as close to the original
> setup as I can test right now).
>
> While the patch fixes the additional key down/up event on longer
> presses, I still get a repeated key event on a short button
> press - which makes it hard to do a single click with the
> remote.

Yes, I've started to notice that too.

> Test on kernel 4.14 with your patch:
> 1510927844.292126: event type EV_MSC(0x04): scancode = 0x1015
> 1510927844.292126: event type EV_KEY(0x01) key_down: KEY_ENTER(0x001c)
> 1510927844.292126: event type EV_SYN(0x00).
> 1510927844.498773: event type EV_MSC(0x04): scancode = 0x1015
> 1510927844.498773: event type EV_SYN(0x00).
> 1510927844.795410: event type EV_KEY(0x01) key_down: KEY_ENTER(0x001c)
> 1510927844.795410: event type EV_SYN(0x00).
> 1510927844.875412: event type EV_KEY(0x01) key_up: KEY_ENTER(0x001c)
> 1510927844.875412: event type EV_SYN(0x00).

There is 875 - 498 = 378ms, which is 200ms IR timeout + 164ms protocol
repeat. This is so long that the repeat delay expired, and that's
where the second keydown comes from.

> Same signal received on kernel 4.9:
> 1510927844.280350: event type EV_MSC(0x04): scancode = 0x1015
> 1510927844.280350: event type EV_KEY(0x01) key_down: KEY_OK(0x0160)
> 1510927844.280350: event type EV_SYN(0x00).
> 1510927844.506477: event type EV_MSC(0x04): scancode = 0x1015
> 1510927844.506477: event type EV_SYN(0x00).
> 1510927844.763111: event type EV_KEY(0x01) key_up: KEY_OK(0x0160)
> 1510927844.763111: event type EV_SYN(0x00).

There it is simply 763 - 506 = 250ms.

> If I understand it correctly it's the input layer repeat (500ms delay)
> kicking in, because time between initial scancode and timeout is
> now signal time + 200ms + 164ms + 200ms (about 570-580ms).
> On older kernels this was signal time + 200ms + 250ms, so typically
> just below the 500ms default repeat delay.
>
> I'm still trying to wrap my head around the timeout code in the
> rc layer. One problem seems to be that we apply the rather large
> timeout twice. Maybe detecting scancodes generated via timeout
> (sth like timestamp - last_timestamp > protocol_repeat_period)
> and in that case immediately signalling keyup could help? Could well
> be that I'm missing somehting important and this is a bad idea.
> I guess I'd better let you figure something out :)

So there is a few complications. For rc-6, if you hold a button down,
there IR repeated every 110ms, which means there is a 69ms space between
the IR keypresses. The trailing space is needed for IR decode.

So with IR timeout of 200ms this will happen:

0.000 rc-6 IR message 1 begins
0.041 rc-6 IR message 1 ends
space
0.110 rc-6 IR message 2 begins; this means that message 1 is decoded now
0.151 rc-6 IR message 2 ends;
space
0.220 rc-6 IR message 3 begins; this means that message 2 is decoded now
0.261 rc-6 IR message 3 ends
space
0.461 IR timeout occurs; this means that message 3 is decoded now

So really the timeout should be length of IR message + IR timeout + error
margin (e.g. rc thread scheduling), unless that is less than the repeat
time.

But this only applies for raw IR decoding; different rules apply for
hardware decoders.

I think for now the best solution is to revert to 250ms for all protocols
(except for cec which needs 550ms), and reconsider for another kernel.

Thanks,
Sean
----
From 2f1135f3f9873778ca5c013d1118710152840cb2 Mon Sep 17 00:00:00 2001
From: Sean Young <sean@mess.org>
Date: Sun, 19 Nov 2017 21:11:17 +0000
Subject: [PATCH] media: rc: partial revert of "media: rc: per-protocol repeat
period"

Since commit d57ea877af38 ("media: rc: per-protocol repeat period"), most
IR protocols have a lower keyup timeout. This causes problems on the
ite-cir, which has default IR timeout of 200ms.

Since the IR decoders read the trailing space, with a IR timeout of 200ms,
the last keydown will have at least a delay of 200ms. This is more than
the protocol timeout of e.g. rc-6 (which is 164ms). As a result the last
IR will be interpreted as a new keydown event, and we get two keypresses.

Revert the protocol timeout to 250ms, except for cec which needs a timeout
of 550ms.

Fixes: d57ea877af38 ("media: rc: per-protocol repeat period")
Cc: <stable@vger.kernel.org> # 4.14
Signed-off-by: Sean Young <sean@mess.org>
---
drivers/media/rc/rc-main.c | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c
index 17950e29d4e3..5057b2ba0c10 100644
--- a/drivers/media/rc/rc-main.c
+++ b/drivers/media/rc/rc-main.c
@@ -39,41 +39,41 @@ static const struct {
[RC_PROTO_UNKNOWN] = { .name = "unknown", .repeat_period = 250 },
[RC_PROTO_OTHER] = { .name = "other", .repeat_period = 250 },
[RC_PROTO_RC5] = { .name = "rc-5",
- .scancode_bits = 0x1f7f, .repeat_period = 164 },
+ .scancode_bits = 0x1f7f, .repeat_period = 250 },
[RC_PROTO_RC5X_20] = { .name = "rc-5x-20",
- .scancode_bits = 0x1f7f3f, .repeat_period = 164 },
+ .scancode_bits = 0x1f7f3f, .repeat_period = 250 },
[RC_PROTO_RC5_SZ] = { .name = "rc-5-sz",
- .scancode_bits = 0x2fff, .repeat_period = 164 },
+ .scancode_bits = 0x2fff, .repeat_period = 250 },
[RC_PROTO_JVC] = { .name = "jvc",
.scancode_bits = 0xffff, .repeat_period = 250 },
[RC_PROTO_SONY12] = { .name = "sony-12",
- .scancode_bits = 0x1f007f, .repeat_period = 100 },
+ .scancode_bits = 0x1f007f, .repeat_period = 250 },
[RC_PROTO_SONY15] = { .name = "sony-15",
- .scancode_bits = 0xff007f, .repeat_period = 100 },
+ .scancode_bits = 0xff007f, .repeat_period = 250 },
[RC_PROTO_SONY20] = { .name = "sony-20",
- .scancode_bits = 0x1fff7f, .repeat_period = 100 },
+ .scancode_bits = 0x1fff7f, .repeat_period = 250 },
[RC_PROTO_NEC] = { .name = "nec",
- .scancode_bits = 0xffff, .repeat_period = 160 },
+ .scancode_bits = 0xffff, .repeat_period = 250 },
[RC_PROTO_NECX] = { .name = "nec-x",
- .scancode_bits = 0xffffff, .repeat_period = 160 },
+ .scancode_bits = 0xffffff, .repeat_period = 250 },
[RC_PROTO_NEC32] = { .name = "nec-32",
- .scancode_bits = 0xffffffff, .repeat_period = 160 },
+ .scancode_bits = 0xffffffff, .repeat_period = 250 },
[RC_PROTO_SANYO] = { .name = "sanyo",
.scancode_bits = 0x1fffff, .repeat_period = 250 },
[RC_PROTO_MCIR2_KBD] = { .name = "mcir2-kbd",
- .scancode_bits = 0xffff, .repeat_period = 150 },
+ .scancode_bits = 0xffff, .repeat_period = 250 },
[RC_PROTO_MCIR2_MSE] = { .name = "mcir2-mse",
- .scancode_bits = 0x1fffff, .repeat_period = 150 },
+ .scancode_bits = 0x1fffff, .repeat_period = 250 },
[RC_PROTO_RC6_0] = { .name = "rc-6-0",
- .scancode_bits = 0xffff, .repeat_period = 164 },
+ .scancode_bits = 0xffff, .repeat_period = 250 },
[RC_PROTO_RC6_6A_20] = { .name = "rc-6-6a-20",
- .scancode_bits = 0xfffff, .repeat_period = 164 },
+ .scancode_bits = 0xfffff, .repeat_period = 250 },
[RC_PROTO_RC6_6A_24] = { .name = "rc-6-6a-24",
- .scancode_bits = 0xffffff, .repeat_period = 164 },
+ .scancode_bits = 0xffffff, .repeat_period = 250 },
[RC_PROTO_RC6_6A_32] = { .name = "rc-6-6a-32",
- .scancode_bits = 0xffffffff, .repeat_period = 164 },
+ .scancode_bits = 0xffffffff, .repeat_period = 250 },
[RC_PROTO_RC6_MCE] = { .name = "rc-6-mce",
- .scancode_bits = 0xffff7fff, .repeat_period = 164 },
+ .scancode_bits = 0xffff7fff, .repeat_period = 250 },
[RC_PROTO_SHARP] = { .name = "sharp",
.scancode_bits = 0x1fff, .repeat_period = 250 },
[RC_PROTO_XMP] = { .name = "xmp", .repeat_period = 250 },
--
2.14.3
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