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 13:49:18 +0100
From:	Benjamin Tissoires <benjamin.tissoires@...c.fr>
To:	Henrik Rydberg <rydberg@...omail.se>
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 Henrik,

On Thu, Jan 27, 2011 at 13:06, Henrik Rydberg <rydberg@...omail.se> wrote:
> 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?

In fact, the idea was to put this on the table again ;). I have no
idea of what is the right think to do in such case.
So I'll take all comments.

>
>> 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.

That was my question. Plus I had a subliminal message in which I
intend you to take the drive on this work. ;)

>
>> 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.

Quick and dirty think. Maybe the old implementation is better.

>
> 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?

same above

>
>> +{
>> +     unsigned int mtmap = code > ABS_MT_FIRST ? code - ABS_MT_FIRST : 0;
>
> Should rather return -EINVAL on bad argument.

I did not know how to handle the original code:
"unsigned int mtmap = input_mt_abs_map[code];"

Now I know.

>
>> +     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().

This is a problem when working with code that was send 6 months ago.

>
>> +     } 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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