linux-kernel - Re: [PATCH] input: mt: introduce MT event slots

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Message-ID: <20100415232523.GA18263@core.coreip.homeip.net>
Date:	Thu, 15 Apr 2010 16:25:25 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] input: mt: introduce MT event slots

Hi Henrik,

On Thu, Apr 08, 2010 at 02:13:10AM +0200, Henrik Rydberg wrote:
> With the rapidly increasing number of intelligent multi-contact and
> multi-user devices, the need to send digested, filtered information
> from a set of different sources within the same device is imminent.
> This patch adds the concept of slots to the MT protocol. The slots
> enumerate a set of identified sources, such that all MT events
> can be passed independently and selectively per identified source.
> 
> The protocol works like this: Instead of sending a SYN_MT_REPORT
> event immediately after the contact data, one sends a SYN_MT_SLOT
> event immediately before the contact data. The input core will only
> emit events for the slots corresponding to the contacts that have
> changed. It is assumed that the same slot is used for the duration
> of an initiated contact.
> 

I see the reason for doing this however I would like to hold off
applying it till we get a couple of users and prove that the scheme
works well for them.

> Signed-off-by: Henrik Rydberg <rydberg@...omail.se>
> ---
>  drivers/input/input.c |   62 +++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/input.h |   26 ++++++++++++++++++++
>  2 files changed, 88 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/input/input.c b/drivers/input/input.c
> index afd4e2b..217e976 100644
> --- a/drivers/input/input.c
> +++ b/drivers/input/input.c
> @@ -181,6 +181,22 @@ static void input_stop_autorepeat(struct input_dev *dev)
>  #define INPUT_PASS_TO_DEVICE	2
>  #define INPUT_PASS_TO_ALL	(INPUT_PASS_TO_HANDLERS | INPUT_PASS_TO_DEVICE)
>  
> +static void input_handle_mt_event(struct input_dev *dev,
> +				  unsigned int code, int value)
> +{
> +	int oldval = dev->mt[dev->slot].abs[code];

A temp for dev->mt[dev->slot] might be nice.

>  
> +/**
> + * struct input_mt_slot - represents the state of an MT input slot
> + * @abs: current values from absolute axes for this slot
> + */
> +struct input_mt_slot {
> +	int abs[ABS_MAX + 1];
> +};

It would be nice to use abs[ABS_MT_MAX - ABS_MT_TOUCH_MAJOR] to save
some memory.

-- 
Dmitry
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