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From: Hans Verkuil <>
To: Ricardo Ribalda Delgado <>,
	Laurent Pinchart <>
Cc: Mauro Carvalho Chehab <>,
	Hans Verkuil <>,
	Sylwester Nawrocki <>,
	Sakari Ailus <>,
	Antti Palosaari <>,
	linux-media <>,
	LKML <>
Subject: Re: [PATCH v4 1/2] media/v4l2-ctrls: Always run s_ctrl on volatile ctrls
Date: Mon, 16 Mar 2015 12:05:05 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 03/09/2015 05:45 PM, Ricardo Ribalda Delgado wrote:
> Hello
> Back from holidays and back to this issue. Sorry for the delay.
>> I'm not sure about Ricardo's use case, is it the one we've discussed on #v4l ?
>> If so, and if I recall correctly, the idea was to perform an action with a
>> parameter, and didn't require volatility.
> In my case, there is a trigger overflow bit. The user acks the trigger
> overflow by writting any value to the control.
> There is no parameter. In that sense it looks like a volatile read + a
> button on a controll.
>> Your proposal is interesting as well, but I'm not sure about the
>> V4L2_CTRL_FLAG_ACTION name. Aren't all controls supposed to have an action of
>> some sort ? That's nitpicking of course.

Actually, usually controls just set some parameter and if the new value is
the same as the old value, then nothing is done at all.

A button control always executes some action immediately.

> What about the name STATELESS_WRITE ? or perhaps VOLATILE_WRITE? I
> dont care about the name :), but better have it solved before I write
> the doc :P


>> Also, should the action flag be automatically set for button controls ? Button
>> controls would in a way become type-less controls with the action flag set,
>> that's interesting. I suppose type-less controls without the action flag don't
>> make sense.

Yes, this flag will be set for button controls. Those are already WRITE_ONLY and
all WRITE_ONLY controls will set the new flag as well.



      reply	other threads:[~2015-03-16 11:05 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-17 15:08 Ricardo Ribalda Delgado
2015-02-23  9:06 ` Hans Verkuil
2015-02-23 23:07   ` Laurent Pinchart
2015-02-24  1:04     ` Ricardo Ribalda Delgado
2015-03-09 16:45     ` Ricardo Ribalda Delgado
2015-03-16 11:05       ` Hans Verkuil [this message]

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