linux-kernel - Re: [PATCH 06/12] iio: adc: ad9467: add mutex to struct ad9467

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Message-ID: <20231204165129.130e189c@jic23-huawei>
Date:   Mon, 4 Dec 2023 16:51:29 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Nuno Sá <noname.nuno@...il.com>
Cc:     Nuno Sa via B4 Relay <devnull+nuno.sa.analog.com@...nel.org>,
        nuno.sa@...log.com, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        Olivier MOYSAN <olivier.moysan@...s.st.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>
Subject: Re: [PATCH 06/12] iio: adc: ad9467: add mutex to struct
 ad9467_state

On Mon, 04 Dec 2023 17:10:01 +0100
Nuno Sá <noname.nuno@...il.com> wrote:

> 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@...nel.org> wrote:
> >   
> > > From: Nuno Sa <nuno.sa@...log.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@...log.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.

Talk about the data or state rather than the access to it.
Something like
'ensure consistent state obtained on multiple related accesses.'
Or if it's RMW then say that.
> 
> - Nuno Sá
> >   
>