linux-kernel - Re: [PATCH v4 4/9] staging:iio:ad7780: add chip ID values and mask

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Date:   Fri, 8 Mar 2019 21:19:29 -0300
From:   Renato Lui Geh <renatogeh@...il.com>
To:     "Ardelean, Alexandru" <Alex.Ardelean@...log.com>
Cc:     "renatogeh@...il.com" <renatogeh@...il.com>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "kernel-usp@...glegroups.com" <kernel-usp@...glegroups.com>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "knaack.h@....de" <knaack.h@....de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "Hennerich, Michael" <Michael.Hennerich@...log.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "giuliano.belinassi@....br" <giuliano.belinassi@....br>,
        "pmeerw@...erw.net" <pmeerw@...erw.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Popa, Stefan Serban" <StefanSerban.Popa@...log.com>
Subject: Re: [PATCH v4 4/9] staging:iio:ad7780: add chip ID values and mask

On 03/04, Ardelean, Alexandru wrote:
>On Sun, 2019-03-03 at 14:53 +0000, Jonathan Cameron wrote:
>> [External]
>>
>>
>> On Sun, 3 Mar 2019 11:01:09 -0300
>> Renato Lui Geh <renatogeh@...il.com> wrote:
>>
>> > On 03/01, Ardelean, Alexandru wrote:
>> > > On Thu, 2019-02-28 at 11:24 -0300, Renato Lui Geh wrote:
>> > > >
>> > > >
>> > > > The ad7780 supports both the ad778x and ad717x families. Each chip
>> > > > has
>> > > > a corresponding ID. This patch provides a mask for extracting ID
>> > > > values
>> > > > from the status bits and also macros for the correct values for the
>> > > > ad7170, ad7171, ad7780 and ad7781.
>> > > >
>> > > > Signed-off-by: Renato Lui Geh <renatogeh@...il.com>
>> > > > ---
>> > > >  drivers/staging/iio/adc/ad7780.c | 8 ++++++--
>> > > >  1 file changed, 6 insertions(+), 2 deletions(-)
>> > > >
>> > > > diff --git a/drivers/staging/iio/adc/ad7780.c
>> > > > b/drivers/staging/iio/adc/ad7780.c
>> > > > index 56c49e28f432..ad7617a3a141 100644
>> > > > --- a/drivers/staging/iio/adc/ad7780.c
>> > > > +++ b/drivers/staging/iio/adc/ad7780.c
>> > > > @@ -26,10 +26,14 @@
>> > > >  #define AD7780_RDY             BIT(7)
>> > > >  #define AD7780_FILTER          BIT(6)
>> > > >  #define AD7780_ERR             BIT(5)
>> > > > -#define AD7780_ID1             BIT(4)
>> > > > -#define AD7780_ID0             BIT(3)
>> > > >  #define AD7780_GAIN            BIT(2)
>> > > >
>> > > > +#define AD7170_ID              0
>> > > > +#define AD7171_ID              1
>> > > > +#define AD7780_ID              1
>> > > > +#define AD7781_ID              0
>> > > > +
>> > > > +#define AD7780_ID_MASK         (BIT(3) | BIT(4))
>> > >
>> > > This also doesn't have any functionality change.
>> > > The AD7170_ID, AD7171_ID, AD7780_ID & AD7781_ID IDs are also unused
>> > > (maybe
>> > > in a later patch they are ?).
>> >
>> > They aren't. I added them following a previous review suggestion.
>> > Should
>> > I remove them?
>>
>> Can we check them?  It's always useful to confirm that the device is
>> the one you think it is.  Then we can either use what is there
>> with a suitable warning, or if that is tricky just fault out as the
>> dt is giving us the wrong part number.
>>
>> J
>
>I guess `dev_warn_ratelimited()` could be used to make sure syslog isn't
>spammed-to-death when doing multiple conversions, and the ID isn't correct.
>Since these IDs are read after you get a sample, I'm a bit fearful of log-
>spam.
>
>I wouldn't throw an error in the ad7780_postprocess_sample() for this, but
>warning [with rate-limit] sounds reasonable.

Looking at dev_warn_ratelimited's definition (and its use in other parts
of the kernel), I see that we'd need the device to be stored somewhere
(perhaps in ad7780_state?) in order for us to pass it as argument to
dev_warn from within postprocess_sample. Should this be stored in
ad7780_state?  Or can I get the spi_device some other way?
>
>>
>> > >
>> > > I would also leave the AD7780_ID1 & AD7780_ID0 definitions in place,
>> > > since
>> > > they're easier matched with the datasheet.
>> > >
>> > > >
>> > > >  #define AD7780_PATTERN_GOOD    1
>> > > >  #define AD7780_PATTERN_MASK    GENMASK(1, 0)
>> > > > --
>> > > > 2.21.0
>> > > >
>>
>>