Re: [PATCH v3 13/13] HID: hid-multitouch: forwards ABS_SCAN_TIME

["Henrik Rydberg" <rydberg@euromail.se>]

Hi Benjamin,

> From: Benjamin Tissoires <benjamin.tissoires@gmail.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@gmail.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?

>  };
>  
>  /* 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?

>  
>  /*
>   * HID report types --- Ouch! HID spec says 1 2 3!
> -- 
> 1.8.0

Thanks,
Henrik