linux-kernel - Re: [RFC 1/2] input: mt: Add method to extract the MT slot state

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Date:	Thu, 27 Jan 2011 13:06:03 +0100
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Benjamin Tissoires <benjamin.tissoires@...c.fr>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Ping Cheng <pingc@...om.com>, Jiri Kosina <jkosina@...e.cz>,
	Chris Bagwell <chris@...bagwell.com>,
	Rafi Rubin <rafi@...s.upenn.edu>,
	Stephane Chatty <chatty@...-enac.fr>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/2] input: mt: Add method to extract the MT slot state

Hi Benjamin,

On Thu, Jan 27, 2011 at 11:35:46AM +0100, Benjamin Tissoires wrote:
> This patch adds the function input_mt_get_abs_value(), which may be

Ehm, input_mt_get_absinfo?

> used to extract the current state of the MT slots.
> 
> Signed-off-by: Henrik Rydberg <rydberg@...omail.se>

I had rather re-add this myself, thanks.

> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...c.fr>
> ---
>  drivers/input/input-mt.c |   32 ++++++++++++++++++++++++++++++++
>  include/linux/input/mt.h |    1 +
>  2 files changed, 33 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c
> index c48c81f..5b95e38 100644
> --- a/drivers/input/input-mt.c
> +++ b/drivers/input/input-mt.c
> @@ -168,3 +168,35 @@ void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count)
>  	}
>  }
>  EXPORT_SYMBOL(input_mt_report_pointer_emulation);
> +
> +/**
> + * input_mt_get_absinfo - retrieve MT state variables from a device slot
> + * @dev: input device which state is being queried
> + * @code: ABS code to retrieve
> + * @slot: slot to retrieve from
> + *
> + * Return the ABS state of the given MT slot. If code is not an MT
> + * event, the corresponding ABS event is returned.
> + *
> + * This function may be called by anyone interested in extracting the
> + * current MT state. Used by evdev handlers.
> + */
> +struct input_absinfo input_mt_get_absinfo(struct input_dev *dev, unsigned int code, int slot)

Why return the struct? Give it a pointer instead, so the return value
can be used for errors.

Also, I wonder about the usefulness of extracting the absinfo here -
only the value depends on the slot argument, and absinfo does not
require the same lock protection. Why not keep the layout from the
original patch?

> +{
> +	unsigned int mtmap = code > ABS_MT_FIRST ? code - ABS_MT_FIRST : 0;

Should rather return -EINVAL on bad argument.

> +	unsigned long flags;
> +	struct input_absinfo retval;
> +
> +	spin_lock_irqsave(&dev->event_lock, flags);
> +	if (!mtmap)
> +		retval = dev->absinfo[code];
> +	else if (slot >= 0 && slot < dev->mtsize) {
> +		retval = dev->absinfo[code];
> +		retval.value = dev->mt[slot].abs[mtmap];

Please use input_mt_get_value().

> +	} else
> +		retval.value = 0;
> +	spin_unlock_irqrestore(&dev->event_lock, flags);
> +
> +	return retval;
> +}
> +EXPORT_SYMBOL(input_mt_get_absinfo);
> diff --git a/include/linux/input/mt.h b/include/linux/input/mt.h
> index b3ac06a..a71a27f 100644
> --- a/include/linux/input/mt.h
> +++ b/include/linux/input/mt.h
> @@ -54,4 +54,5 @@ void input_mt_report_slot_state(struct input_dev *dev,
>  void input_mt_report_finger_count(struct input_dev *dev, int count);
>  void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count);
>  
> +struct input_absinfo input_mt_get_absinfo(struct input_dev *dev, unsigned int code, int slot);
>  #endif

Thanks,
Henrik
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