linux-kernel - Re: [PATCH 4/4] iio: ti_am335x_adc: Add continuous sampling and trigger support

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Date:	Tue, 20 Aug 2013 17:26:58 +0100
From:	"Zubair Lutfullah :" <zubair.lutfullah@...il.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Zubair Lutfullah <zubair.lutfullah@...il.com>, jic23@....ac.uk,
	dmitry.torokhov@...il.com, linux-iio@...r.kernel.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, Russ.Dill@...com
Subject: Re: [PATCH 4/4] iio: ti_am335x_adc: Add continuous sampling and
 trigger support

On Mon, Aug 19, 2013 at 07:12:38PM +0200, Sebastian Andrzej Siewior wrote:
> * Zubair Lutfullah | 2013-08-13 21:05:03 [+0100]:
> 
> >diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> >index 3ceac3e..0d7e313 100644
> >--- a/drivers/iio/adc/ti_am335x_adc.c
> >+++ b/drivers/iio/adc/ti_am335x_adc.c
> …
> >+static irqreturn_t tiadc_irq(int irq, void *private)
> >+{
> …
> >+		wake_up_interruptible(&adc_dev->wq_data_avail);
> …
> >+}
> …
> >+static irqreturn_t tiadc_trigger_h(int irq, void *p)
> >+{
> …
> >+	schedule_work(&adc_dev->poll_work);
> …
> >+}
> …
> >+static void tiadc_adc_work(struct work_struct *work_s)
> >+{
> …
> >+		wait_event_interruptible(adc_dev->wq_data_avail,
> >+					(adc_dev->data_avail == 1));
> …
> >+}
> 
> This is not very nice. The problem is that you might sleep in a
> workqueue and so the other jobs will wait until you are done. I'm think
This will change to a different style.

> I'm looking into DMA support for this so once your code is working it
> should be possible to switch to DMA instead reading byte wise from the
> fifo.
Great.

> How did you test the whole thing? Do you have a test program which
> selects a few sources and reads them in continuous mode?
> 
generic_buffer.c runs for this for sysfs trigger.. 
However. If you follow the other thread. 
This is obsolete and trigger style is changing to a driver trigger.

I'll update when I'm done.

Thanks
ZubairLK
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