Re: [PATCH 06/12] iio: adc: ad9467: add mutex to struct ad9467_state

From: "Nuno Sá" <noname.nuno@gmail.com>
To: Jonathan Cameron <jic23@kernel.org>,
	Nuno Sa via B4 Relay  <devnull+nuno.sa.analog.com@kernel.org>
Cc: nuno.sa@analog.com, linux-kernel@vger.kernel.org,
	devicetree@vger.kernel.org, linux-iio@vger.kernel.org,
	Olivier MOYSAN <olivier.moysan@foss.st.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Michael Hennerich <Michael.Hennerich@analog.com>
Subject: Re: [PATCH 06/12] iio: adc: ad9467: add mutex to struct ad9467_state
Date: Mon, 04 Dec 2023 17:10:01 +0100	[thread overview]
Message-ID: <69a7ca77055fc57cff6d6be95fb5796723171230.camel@gmail.com> (raw)
In-Reply-To: <20231204152301.6c212539@jic23-huawei>

On Mon, 2023-12-04 at 15:23 +0000, Jonathan Cameron wrote:
> On Tue, 21 Nov 2023 11:20:19 +0100
> Nuno Sa via B4 Relay <devnull+nuno.sa.analog.com@kernel.org> wrote:
> 
> > From: Nuno Sa <nuno.sa@analog.com>
> > 
> > When calling ad9467_set_scale(), multiple calls to ad9467_spi_write()
> > are done which means we need to properly protect the whole operation so
> > we are sure we will be in a sane state if two concurrent calls occur.
> > 
> > Fixes: ad6797120238 ("iio: adc: ad9467: add support AD9467 ADC")
> > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> > ---
> >  drivers/iio/adc/ad9467.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iio/adc/ad9467.c b/drivers/iio/adc/ad9467.c
> > index 04474dbfa631..91821dee03b7 100644
> > --- a/drivers/iio/adc/ad9467.c
> > +++ b/drivers/iio/adc/ad9467.c
> > @@ -4,7 +4,7 @@
> >   *
> >   * Copyright 2012-2020 Analog Devices Inc.
> >   */
> > -
> > +#include <linux/cleanup.h>
> >  #include <linux/module.h>
> >  #include <linux/mutex.h>
> >  #include <linux/device.h>
> > @@ -122,6 +122,8 @@ struct ad9467_state {
> >         unsigned int                    output_mode;
> >  
> >         struct gpio_desc                *pwrdown_gpio;
> > +       /* protect against concurrent accesses to the device */
> Not very specific.  Concurrent access usually fine at granularity of
> individual read/write as the bus locks protect it.  What state
> is actually being protected?  A shared buffer or some state that we
> need to ensure remains consistent between driver and device?

At this point not any buffer/data... Just making sure things remain consistent
(typical case when you have multiple reads/writes to the device). That's why a tried
to emphasize "accesses to the device". Maybe I should make it explicit I'm speaking
about multiple reads/writes.

- Nuno Sá
> 