linux-kernel - Re: [PATCH 2/2 v2] HID: magicmouse: Implement Multi-touch Protocol B (MT-B)

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Date:	Tue, 3 Jul 2012 21:12:58 +0200
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Yufeng Shen <miletus@...omium.org>
Cc:	linux-input@...r.kernel.org, Jiri Kosina <jkosina@...e.cz>,
	linux-kernel@...r.kernel.org, Daniel Kurtz <djkurtz@...omium.org>,
	Andrew de los Reyes <adlr@...omium.org>,
	Chase Douglas <chase.douglas@...onical.com>
Subject: Re: [PATCH 2/2 v2] HID: magicmouse: Implement Multi-touch Protocol B
 (MT-B)

Hi Yufeng,

> The driver for Apple Magic Trackpad/Mouse currently uses
> Multi-touch Protocol A (MT-A) to report touch events and uses
> ABS_MT_TRACKING_ID to do finger tracking. The fact of the device
> being able to track individual finger makes it possible to
> report touch events using MT-B. This patch converts the driver
> to use MT-B as it is preferred to MT-A.
> 
> V2: Converting entirely to MT-B as Henrik Rydberg suggested.
> 
> Signed-off-by: Yufeng Shen <miletus@...omium.org>
> ---
>  drivers/hid/hid-magicmouse.c |   26 +++++++++++++++++++-------
>  1 files changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
> index fd88f21..0d6957e 100644
> --- a/drivers/hid/hid-magicmouse.c
> +++ b/drivers/hid/hid-magicmouse.c
> @@ -16,6 +16,7 @@
>  
>  #include <linux/device.h>
>  #include <linux/hid.h>
> +#include <linux/input/mt.h>
>  #include <linux/module.h>
>  #include <linux/slab.h>
>  #include <linux/usb.h>
> @@ -271,9 +272,11 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
>  	} else if (msc->single_touch_id == id)
>  		msc->single_touch_id = SINGLE_TOUCH_UP;
>  
> +	input_mt_slot(input, id);
> +	input_mt_report_slot_state(input, MT_TOOL_FINGER, down);
> +
>  	/* Generate the input events for this touch. */
>  	if (down) {
> -		input_report_abs(input, ABS_MT_TRACKING_ID, id);
>  		input_report_abs(input, ABS_MT_TOUCH_MAJOR, touch_major << 2);
>  		input_report_abs(input, ABS_MT_TOUCH_MINOR, touch_minor << 2);
>  		input_report_abs(input, ABS_MT_ORIENTATION, -orientation);
> @@ -286,8 +289,6 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
>  			else /* USB_DEVICE_ID_APPLE_MAGICTRACKPAD */
>  				input_event(input, EV_MSC, MSC_RAW, tdata[8]);
>  		}
> -
> -		input_mt_sync(input);
>  	}
>  }
>  
> @@ -383,8 +384,10 @@ static int magicmouse_raw_event(struct hid_device *hdev,
>  	return 1;
>  }
>  
> -static void magicmouse_setup_input(struct input_dev *input, struct hid_device *hdev)
> +static int magicmouse_setup_input(struct input_dev *input, struct hid_device *hdev)
>  {
> +	int error;
> +
>  	__set_bit(EV_KEY, input->evbit);
>  
>  	if (input->id.product == USB_DEVICE_ID_APPLE_MAGICMOUSE) {
> @@ -421,7 +424,9 @@ static void magicmouse_setup_input(struct input_dev *input, struct hid_device *h
>  
>  	__set_bit(EV_ABS, input->evbit);
>  
> -	input_set_abs_params(input, ABS_MT_TRACKING_ID, 0, 15, 0, 0);
> +	error = input_mt_init_slots(input, 16);
> +	if (error)
> +		return error;
>  	input_set_abs_params(input, ABS_MT_TOUCH_MAJOR, 0, 255 << 2,
>  			     4, 0);
>  	input_set_abs_params(input, ABS_MT_TOUCH_MINOR, 0, 255 << 2,
> @@ -468,6 +473,8 @@ static void magicmouse_setup_input(struct input_dev *input, struct hid_device *h
>  		__set_bit(EV_MSC, input->evbit);
>  		__set_bit(MSC_RAW, input->mscbit);
>  	}
> +
> +	return 0;
>  }
>  
>  static int magicmouse_input_mapping(struct hid_device *hdev,
> @@ -523,8 +530,13 @@ static int magicmouse_probe(struct hid_device *hdev,
>  	/* We do this after hid-input is done parsing reports so that
>  	 * hid-input uses the most natural button and axis IDs.
>  	 */
> -	if (msc->input)
> -		magicmouse_setup_input(msc->input, hdev);
> +	if (msc->input) {
> +		ret = magicmouse_setup_input(msc->input, hdev);
> +		if (ret) {
> +			hid_err(hdev, "magicmouse setup input failed\n");

Error codes are usually meaningful, so printing it here is a good idea.

> +			goto err_stop_hw;
> +		}
> +	}
>  
>  	if (id->product == USB_DEVICE_ID_APPLE_MAGICMOUSE)
>  		report = hid_register_report(hdev, HID_INPUT_REPORT,
> -- 
> 1.7.7.3
> 

In addition to the above, which looks correct thank you, please
replace the explicit BTN_TOOL events and the single_touch_id logic
with input_mt_report_pointer_emulation(input, true).

Thanks,
Henrik
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