linux-kernel - Re: [PATCH v8 2/2] iio: adc: Add ti-ads1018 driver

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Message-ID: <20251216182106.000051c3@huawei.com>
Date: Tue, 16 Dec 2025 18:21:06 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: David Lechner <dlechner@...libre.com>
CC: Kurt Borja <kuurtb@...il.com>, Jonathan Cameron <jic23@...nel.org>, "Rob
 Herring" <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, "Conor
 Dooley" <conor+dt@...nel.org>, Tobias Sperling <tobias.sperling@...ting.com>,
	Nuno Sá <nuno.sa@...log.com>, Andy Shevchenko
	<andy@...nel.org>, <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 2/2] iio: adc: Add ti-ads1018 driver

On Mon, 15 Dec 2025 12:09:31 -0600
David Lechner <dlechner@...libre.com> wrote:

> On 12/15/25 10:54 AM, Kurt Borja wrote:
> > On Mon Dec 15, 2025 at 10:55 AM -05, David Lechner wrote:  
> >> On 12/11/25 10:25 PM, Kurt Borja wrote:  
> >>> Add ti-ads1018 driver for Texas Instruments ADS1018 and ADS1118 SPI
> >>> analog-to-digital converters.
> >>>  
> 
> ...
> 
> >>> +static irqreturn_t ads1018_trigger_handler(int irq, void *p)
> >>> +{
> >>> +	struct iio_poll_func *pf = p;
> >>> +	struct iio_dev *indio_dev = pf->indio_dev;
> >>> +	struct ads1018 *ads1018 = iio_priv(indio_dev);
> >>> +	struct {
> >>> +		__be16 conv;
> >>> +		aligned_s64 ts;
> >>> +	} scan = {};
> >>> +	int ret;
> >>> +  
> >>
> >>  
> >>> +	if (iio_device_claim_buffer_mode(indio_dev))
> >>> +		goto out_notify_done;  
> >>
> >> This should not be needed. It should not be possible to
> >> exit buffer mode without triggers being stopped first.
> >> (No other driver is doing this.)  
> > 
> > Previously I had my own lock here because ads1018_spi_read_exclusive()
> > needs locking.  
> 
> What exactly are we protecting against here? I.e. give side-by-side
> lists of possible concurrent function calls where there could be a
> problem.
> 
> Any call to iio_device_claim_direct() will already fail without
> calling iio_device_claim_buffer_mode() here. And since this is
> an interrupt handler, we don't have to worry about reentrancy (it
> can't be called again until the previous call returns). And nowhere
> else in the driver is calling iio_device_claim_buffer_mode(). So
> calling it here doesn't actually add any protection AFAICT.

Agreed we shouldn't need this. Given these comment and my lazy nature,
Kurt, would you mind spinning a patch on top of this series that I can
squash with it on my tree?  That should be easier to review than
a full v9.  If you prefer a v9 of the whole thing, that would be fine too.

Thanks,

Jonathan
> 
> > I dropped it per your suggestion in v1 I believe, but
> > given the discussion in the cleanup.h series I was thinking in bringing
> > it back.
> > 
> > But yes, the scope can be adjusted too.
> >   
>