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Message-ID: <69a7ca77055fc57cff6d6be95fb5796723171230.camel@gmail.com>
Subject: Re: [PATCH 06/12] iio: adc: ad9467: add mutex to struct ad9467_state
From:   Nuno =?ISO-8859-1?Q?S=E1?= <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>
Date:   Mon, 04 Dec 2023 17:10:01 +0100
In-Reply-To: <20231204152301.6c212539@jic23-huawei>
References: <20231121-dev-iio-backend-v1-0-6a3d542eba35@analog.com>
         <20231121-dev-iio-backend-v1-6-6a3d542eba35@analog.com>
         <20231204152301.6c212539@jic23-huawei>
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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:
>=20
> > From: Nuno Sa <nuno.sa@analog.com>
> >=20
> > 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.
> >=20
> > Fixes: ad6797120238 ("iio: adc: ad9467: add support AD9467 ADC")
> > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> > ---
> > =C2=A0drivers/iio/adc/ad9467.c | 6 +++++-
> > =C2=A01 file changed, 5 insertions(+), 1 deletion(-)
> >=20
> > 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 @@
> > =C2=A0 *
> > =C2=A0 * Copyright 2012-2020 Analog Devices Inc.
> > =C2=A0 */
> > -
> > +#include <linux/cleanup.h>
> > =C2=A0#include <linux/module.h>
> > =C2=A0#include <linux/mutex.h>
> > =C2=A0#include <linux/device.h>
> > @@ -122,6 +122,8 @@ struct ad9467_state {
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0unsigned int=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0output_mode;
> > =C2=A0
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct gpio_desc=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0*pwrdown_gpio;
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0/* protect against concurren=
t accesses to the device */
> Not very specific.=C2=A0 Concurrent access usually fine at granularity of
> individual read/write as the bus locks protect it.=C2=A0 What state
> is actually being protected?=C2=A0 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 consist=
ent
(typical case when you have multiple reads/writes to the device). That's wh=
y a tried
to emphasize "accesses to the device". Maybe I should make it explicit I'm =
speaking
about multiple reads/writes.

- Nuno S=C3=A1
>=20