linux-kernel - Re: [PATCH v2 05/11] HID: hid-multitouch: get maxcontacts also from logical

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Date:	Mon, 29 Oct 2012 22:52:19 +0100
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>
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 v2 05/11] HID: hid-multitouch: get maxcontacts also from
 logical_max value

On Fri, Oct 26, 2012 at 10:44:21AM +0200, Benjamin Tissoires wrote:
> Win8 devices are required to present the feature "Maximum Contact Number".
> Fortunately all win7 devices I've seen presents this feature.
> If the current value is 0, then, the driver can get the actual supported
> contact count by refering to the logical_max.
> This win8 specification ensures that logical_max may not be above 250.
> This also allows us to detect when devices like irtouch or stantum reports
> an obviously wrong value of 255.
> 
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...il.com>
> ---
>  drivers/hid/hid-multitouch.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
> index 95562d8..41f2981 100644
> --- a/drivers/hid/hid-multitouch.c
> +++ b/drivers/hid/hid-multitouch.c
> @@ -121,6 +121,7 @@ struct mt_device {
>  #define MT_CLS_GENERALTOUCH_PWT_TENFINGERS	0x0109
>  
>  #define MT_DEFAULT_MAXCONTACT	10
> +#define MT_MAX_MAXCONTACT	250
>  
>  #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)
> @@ -283,6 +284,9 @@ static void mt_feature_mapping(struct hid_device *hdev,
>  	case HID_DG_CONTACTMAX:
>  		td->maxcontact_report_id = field->report->id;
>  		td->maxcontacts = field->value[0];
> +		if (!td->maxcontacts &&
> +		    field->logical_maximum <= MT_MAX_MAXCONTACT)
> +			td->maxcontacts = field->logical_maximum;
>  		if (td->mtclass.maxcontacts)
>  			/* check if the maxcontacts is given by the class */
>  			td->maxcontacts = td->mtclass.maxcontacts;
> -- 
> 1.7.11.7
> 

Acked-by: Henrik Rydberg <rydberg@...omail.se>
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