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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Wed, 11 Nov 2020 16:46:27 +0200
Message-ID: <CAHp75VcKmiBM1WQTtmJ7L3kpB1xdXX=xOtM2zCAtaszXBcHokg@mail.gmail.com>
Subject: Re: [PATCH] spi: Add SPI_NO_TX/RX support
To:     Alexandru Ardelean <alexandru.ardelean@analog.com>
Cc:     linux-spi <linux-spi@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Mark Brown <broonie@kernel.org>,
        "Bogdan, Dragos" <dragos.bogdan@analog.com>,
        Alexandru Ardelean <ardeleanalex@gmail.com>
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On Wed, Nov 11, 2020 at 4:13 PM Alexandru Ardelean
<alexandru.ardelean@analog.com> wrote:
>
> From: Dragos Bogdan <dragos.bogdan@analog.com>
>
> Transmit/receive only is a valid SPI mode. For example, the MOSI/TX line
> might be missing from an ADC while for a DAC the MISO/RX line may be
> optional. This patch adds these two new modes: SPI_NO_TX and
> SPI_NO_RX. This way, the drivers will be able to identify if any of
> these two lines is missing and to adjust the transfers accordingly.

Shouldn't this update a binding documentation?

...

> -       /* check mode to prevent that DUAL and QUAD set at the same time
> +       /* check mode to prevent that any two of DUAL, QUAD and NO_MOSI/MISO
> +        * are set at the same time
>          */

/*
 * Perhaps switch to proper multi-line comment style
 * at the same time?
 */

...

>  #define        SPI_TX_OCTAL    0x2000                  /* transmit with 8 wires */
>  #define        SPI_RX_OCTAL    0x4000                  /* receive with 8 wires */
>  #define        SPI_3WIRE_HIZ   0x8000                  /* high impedance turnaround */
> +#define        SPI_NO_TX       0x10000                 /* no transmit wire */
> +#define        SPI_NO_RX       0x20000                 /* no receive wire */

Perhaps switch to use BIT() instead at some point (as a prerequisite
patch, for example)

-- 
With Best Regards,
Andy Shevchenko