linux-kernel - Re: [PATCH v2 1/2] iio: adc: ti-ads8344: properly byte swap value

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Message-ID: <20200417142345.GA34509@piout.net>
Date:   Fri, 17 Apr 2020 16:23:45 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] iio: adc: ti-ads8344: properly byte swap value

On 17/04/2020 16:45:05+0300, Andy Shevchenko wrote:
> On Thu, Apr 16, 2020 at 11:55 PM Alexandre Belloni
> <alexandre.belloni@...tlin.com> wrote:
> >
> > The first received byte is the MSB, followed by the LSB so the value needs
> > to be byte swapped.
> >
> > Also, the ADC actually has a delay of one clock on the SPI bus. Read three
> > bytes to get the last bit.
> 
> > +       return adc->rx_buf[0] << 9 | adc->rx_buf[1] << 1 | adc->rx_buf[2] >> 7;
> 
> I just realize, isn't it an open coded variant of ror() / rol()?
> 

No, this byteswaps and rotates.


-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com