linux-kernel - Re: [PATCH 2/2] iio: ti_am335x_adc: Add continuous sampling support

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Date:	Wed, 28 Aug 2013 19:19:52 +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,
	lee.jones@...aro.org, linux-iio@...r.kernel.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org
Subject: Re: [PATCH 2/2] iio: ti_am335x_adc: Add continuous sampling support

On Wed, Aug 28, 2013 at 06:43:08PM +0200, Sebastian Andrzej Siewior wrote:
> * Zubair Lutfullah | 2013-08-25 23:45:24 [+0100]:
> 
> >diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> >index a952538..ae2202b 100644
> >--- a/drivers/iio/adc/ti_am335x_adc.c
> >+++ b/drivers/iio/adc/ti_am335x_adc.c
> >@@ -231,28 +406,56 @@ static int tiadc_probe(struct platform_device *pdev)
> …
> >+err_free_device:
> >+	iio_device_free(indio_dev);
> 
> I am not sure about this one.

If I understand correctly, if devm_iio_device_alloc 
is successful earlier in the code and subsequent stuff fails. 

Then the code jumps to err_free_device and this is needed.

> 
> >+err_ret:
> > 	return err;
> > }
> > 
> >@@ -262,11 +465,14 @@ static int tiadc_remove(struct platform_device *pdev)
> > 	struct tiadc_device *adc_dev = iio_priv(indio_dev);
> > 	u32 step_en;
> > 
> >+	free_irq(adc_dev->irq, indio_dev);
> > 	iio_device_unregister(indio_dev);
> >+	iio_buffer_unregister(indio_dev);
> > 	tiadc_channels_remove(indio_dev);
> > 
> > 	step_en = get_adc_step_mask(adc_dev);
> > 	am335x_tsc_se_clr(adc_dev->mfd_tscadc, step_en);
> >+	iio_device_free(indio_dev);
> 
> But this one is wrong. The will be removed via dev_res() and if you do
> it here as well then dev_res() will decrement the reference of an unused
> object.
I was unaware of this aspect.

*but*

iio_simple_dummy.c has it in its remove function.
And I just checked and found it in several drivers as well.

I'll leave this to the more experienced folks on the list..
> > 
> > 	return 0;
> > }
> 
> Sebastian
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