linux-kernel - Re: [PATCH v2 1/1] input: add driver for Bosch Sensortec's BMA150 accelerometer

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Date:	Thu, 23 Jun 2011 13:55:33 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Eric Andersson <eric.andersson@...xphere.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	zhengguang.guo@...ch-sensortec.com, stefan.nilsson@...xphere.com,
	Albert Zhang <xu.zhang@...ch-sensortec.com>
Subject: Re: [PATCH v2 1/1] input: add driver for Bosch Sensortec's BMA150
 accelerometer

On Thu, Jun 23, 2011 at 04:36:31PM +0100, Alan Cox wrote:
> > +
> > +
> > +What:		/sys/bus/i2c/devices/<busnum>-<devaddr>/value
> > +Date:		May 2011
> > +Contact:	Eric Andersson <eric.andersson@...xphere.com>
> > +Description:	This is used to get the current acceleration values for each
> > +		axis. The values are represented as (x,y,z), where each axis can
> > +		hold a value between -512 and 511.
> > +
> > +		Reading: returns the current acceleration values.
> 
> This was nacked in the bma023 driver by the IIO folks - and Dmitry
> pointed out you can do this without a sysfs hack. The trick is to do an
> initial poll in input_open at which point the ioctl query for the
> position will have data that is current and open/ioctl/close works and
> providing we go nail that into other drivers that need that kind of use
> the API is generic and input event based.
> 

Right, I think the patch below will do what is needed for all polled
devices.

Thanks.

-- 
Dmitry


Input: polldev - immediately poll device upon opening

To allow open/ioctl(EVIOCGABS)/close use pattern for polled devices read
the device in context of open() call instead of offloading the first read
to a workqueue. This will ensure that once call to open() returns device
would have cached reasonably recent axis values that can be retrieved via
appropriate ioctl.

Signed-off-by: Dmitry Torokhov <dtor@...l.ru>
---

 drivers/input/input-polldev.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)


diff --git a/drivers/input/input-polldev.c b/drivers/input/input-polldev.c
index b1aabde..b253973 100644
--- a/drivers/input/input-polldev.c
+++ b/drivers/input/input-polldev.c
@@ -49,8 +49,10 @@ static int input_open_polled_device(struct input_dev *input)
 		dev->open(dev);
 
 	/* Only start polling if polling is enabled */
-	if (dev->poll_interval > 0)
-		queue_delayed_work(system_freezable_wq, &dev->work, 0);
+	if (dev->poll_interval > 0) {
+		dev->poll(dev);
+		input_polldev_queue_work(dev);
+	}
 
 	return 0;
 }
--
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