linux-kernel - Re: [PATCH] HID: multitouch: do not init reports for multitouch devices

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Message-ID: <20130718192416.GA526@polaris.bitmath.org>
Date:	Thu, 18 Jul 2013 21:24:16 +0200
From:	rydberg@...omail.se
To:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:	Benjamin Tissoires <benjamin.tissoires@...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] HID: multitouch: do not init reports for multitouch
 devices

Hi Benjamin,

> Some multitouch screens do not like to be polled for input reports.
> However, the Win8 spec says that all touches should be sent during
> each report, making the initialization of reports unnecessary.
> The Win7 spec is less precise, but we can safely assume that when
> the module is loaded (at boot), no one is touching the screen.
> 
> Add the quirk HID_QUIRK_NO_INIT_REPORTS so that we do not have to
> introduce a quirk for each problematic device.

I assume you have tested thoroughly for regressions? How about odd
eGalax devices, for instance? Changes affecting existing hardware
makes me nervous. Is it so bad to add this quirk on a per-device
basis? Or perhaps turned on by default for win8 devices only?

> 
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> ---
>  drivers/hid/hid-multitouch.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
> index d99b959..197c2e6 100644
> --- a/drivers/hid/hid-multitouch.c
> +++ b/drivers/hid/hid-multitouch.c
> @@ -957,6 +957,15 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>  	hdev->quirks |= HID_QUIRK_NO_INPUT_SYNC;
>  
>  	/*
> +	 * Some multitouch screens do not like to be polled for input reports.
> +	 * However, the Win8 spec says that all touches should be sent during
> +	 * each report, making the initialization of reports unnecessary.
> +	 * The Win7 spec is less precise, but we can safely assume that when
> +	 * the module is loaded (at boot), no one is touching the screen.
> +	 */
> +	hdev->quirks |= HID_QUIRK_NO_INIT_REPORTS;
> +
> +	/*
>  	 * This allows the driver to handle different input sensors
>  	 * that emits events through different reports on the same HID
>  	 * device.
> -- 
> 1.8.3.1
> 

Thanks,
Henrik
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