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Date: Tue, 13 Nov 2012 18:45:07 +0100
From: Benjamin Tissoires <benjamin.tissoires@...il.com>
To: Henrik Rydberg <rydberg@...omail.se>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>,
Jiri Kosina <jkosina@...e.cz>,
Stephane Chatty <chatty@...c.fr>, linux-input@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 13/13] HID: hid-multitouch: forwards ABS_SCAN_TIME
Hi Henrik,
On Tue, Nov 13, 2012 at 6:27 PM, Henrik Rydberg <rydberg@...omail.se> wrote:
> Hi Benjamin,
>
>> From: Benjamin Tissoires <benjamin.tissoires@...il.com>
>> Date: Tue, 13 Nov 2012 15:12:17 +0100
>> Subject: [PATCH v4] HID: hid-multitouch: forwards MSC_TIMESTAMP
>>
>> Computes the device timestamp according to the specification.
>> It also ensures that if the time between two events is greater
>> than MAX_TIMESTAMP_INTERVAL, the timestamp will be reset.
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...il.com>
>> ---
>> drivers/hid/hid-multitouch.c | 46 +++++++++++++++++++++++++++++++++++++++++---
>> include/linux/hid.h | 1 +
>> 2 files changed, 44 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
>> index caf0f0b..3f8432d 100644
>> --- a/drivers/hid/hid-multitouch.c
>> +++ b/drivers/hid/hid-multitouch.c
>> @@ -32,6 +32,7 @@
>> #include <linux/slab.h>
>> #include <linux/usb.h>
>> #include <linux/input/mt.h>
>> +#include <linux/jiffies.h>
>
> Why?
>
>> #include "usbhid/usbhid.h"
>>
>>
>> @@ -98,6 +99,9 @@ struct mt_device {
>> bool serial_maybe; /* need to check for serial protocol */
>> bool curvalid; /* is the current contact valid? */
>> unsigned mt_flags; /* flags to pass to input-mt */
>> + __s32 dev_time; /* the scan time provided by the device */
>> + unsigned long jiffies; /* the frame's jiffies */
>> + unsigned timestamp; /* the timestamp to be sent */
>
> Why not just dev_time here?
because max dev_time is at least 65535 according to the norm, and the
win 8 device I have has his max value of 65535.
Which means that every 6 seconds and a half the counter resets, and
the value is not properly reset in the way I understand the
specification. The device just forwards an internal clock that is
never reset.
So if you wait 653500 us + 8ms, everything happens as if the device
sent this frame right after the previous one (you get the same value).
I think that it's the job of the kernel to provide clean and coherent
values through evdev, which won't be the case if the jiffies thing is
not in place: every devices will have a different behavior, leading to
complicate things in the user-space.
>
>> };
>>
>> /* classes of device behavior */
>> @@ -126,6 +130,8 @@ struct mt_device {
>> #define MT_DEFAULT_MAXCONTACT 10
>> #define MT_MAX_MAXCONTACT 250
>>
>> +#define MAX_TIMESTAMP_INTERVAL 500000
>> +
>
> Needs to be done in userland anyways, so no need to check this in the kernel.
>
>> #define MT_USB_DEVICE(v, p) HID_DEVICE(BUS_USB, HID_GROUP_MULTITOUCH, v, p)
>> #define MT_BT_DEVICE(v, p) HID_DEVICE(BUS_BLUETOOTH, HID_GROUP_MULTITOUCH, v, p)
>>
>> @@ -451,12 +457,19 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>> mt_store_field(usage, td, hi);
>> td->last_field_index = field->index;
>> return 1;
>> + case HID_DG_SCANTIME:
>> + hid_map_usage(hi, usage, bit, max,
>> + EV_MSC, MSC_TIMESTAMP);
>> + set_bit(MSC_TIMESTAMP, hi->input->mscbit);
>> + td->last_field_index = field->index;
>> + return 1;
>> case HID_DG_CONTACTCOUNT:
>> td->last_field_index = field->index;
>> return 1;
>> case HID_DG_CONTACTMAX:
>> - /* we don't set td->last_slot_field as contactcount and
>> - * contact max are global to the report */
>> + /* we don't set td->last_slot_field as scan time,
>> + * contactcount and contact max are global to the
>> + * report */
>> td->last_field_index = field->index;
>> return -1;
>> }
>> @@ -485,7 +498,8 @@ static int mt_input_mapped(struct hid_device *hdev, struct hid_input *hi,
>> struct hid_field *field, struct hid_usage *usage,
>> unsigned long **bit, int *max)
>> {
>> - if (usage->type == EV_KEY || usage->type == EV_ABS)
>> + if (usage->type == EV_KEY || usage->type == EV_ABS ||
>> + usage->type == EV_MSC)
>> set_bit(usage->type, hi->input->evbit);
>>
>> return -1;
>> @@ -565,11 +579,34 @@ static void mt_complete_slot(struct mt_device *td, struct input_dev *input)
>> */
>> static void mt_sync_frame(struct mt_device *td, struct input_dev *input)
>> {
>> + input_event(input, EV_MSC, MSC_TIMESTAMP, td->timestamp);
>
> I think this should go after the frame sync,
>
>> input_mt_sync_frame(input);
>
> And the computation (100 * td->dev_time) should work fine. It will wrap
> properly.
>
>> input_sync(input);
>> td->num_received = 0;
>> }
>>
>> +static void mt_compute_timestamp(struct mt_device *td, struct hid_field *field,
>> + __s32 value)
>> +{
>> + long delta = value - td->dev_time;
>> + unsigned long jdelta = jiffies_to_usecs(jiffies - td->jiffies);
>> +
>> + td->jiffies = jiffies;
>> + td->dev_time = value;
>> +
>> + if (delta < 0)
>> + delta += field->logical_maximum;
>> +
>> + /* HID_DG_SCANTIME is expressed in 100us, we want it in ms. */
>> + delta *= 100;
>> +
>> + if (abs(delta - jdelta) > MAX_TIMESTAMP_INTERVAL)
>> + /* obviously wrong clock -> the device time has been reset */
>> + td->timestamp = 0;
>> + else
>> + td->timestamp += delta;
>> +}
>> +
>
> Can be skipped entirely.
>
>> static int mt_event(struct hid_device *hid, struct hid_field *field,
>> struct hid_usage *usage, __s32 value)
>> {
>> @@ -617,6 +654,9 @@ static int mt_event(struct hid_device *hid, struct hid_field *field,
>> case HID_DG_HEIGHT:
>> td->curdata.h = value;
>> break;
>> + case HID_DG_SCANTIME:
>> + mt_compute_timestamp(td, field, value);
>
> Just td->dev_time = value should work fine here.
>
>> + break;
>> case HID_DG_CONTACTCOUNT:
>> /*
>> * Includes multi-packet support where subsequent
>> diff --git a/include/linux/hid.h b/include/linux/hid.h
>> index 6b4f322..0337e50 100644
>> --- a/include/linux/hid.h
>> +++ b/include/linux/hid.h
>> @@ -279,6 +279,7 @@ struct hid_item {
>> #define HID_DG_DEVICEINDEX 0x000d0053
>> #define HID_DG_CONTACTCOUNT 0x000d0054
>> #define HID_DG_CONTACTMAX 0x000d0055
>> +#define HID_DG_SCANTIME 0x000d0056
>
> Was this missing this the old patch, or did it get moved here?
Sorry for that. I moved it there because I cleaned a little the other
patch by removing the hid things.
Cheers,
Benjamin
>
>>
>> /*
>> * HID report types --- Ouch! HID spec says 1 2 3!
>> --
>> 1.8.0
>
> Thanks,
> Henrik
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