linux-kernel - Re: [PATCH v4 2/3] spi: Add SPI_NO

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Message-ID: <CAHp75Veh=b0JYOP_gETyqqGGEYhO9JcxFCGXSuzSX27-qioprA@mail.gmail.com>
Date:   Thu, 3 Dec 2020 16:10:02 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc:     linux-spi <linux-spi@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Bogdan, Dragos" <dragos.bogdan@...log.com>
Subject: Re: [PATCH v4 2/3] spi: Add SPI_NO_TX/RX support

On Thu, Dec 3, 2020 at 4:00 PM Alexandru Ardelean
<alexandru.ardelean@...log.com> wrote:
> From: Dragos Bogdan <dragos.bogdan@...log.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.

...

> +       BUILD_BUG_ON(SPI_MODE_USER_MASK & SPI_MODE_KERNEL_MASK);

Please, use static_assert() as I have been pointed out. It may be
located outside of a function scope. You may attach it directly to the
definition of the KERNEL_MASK (I haven't tried yet with header
though).

...

> +#define SPI_NO_TX      BIT(31)         /* no transmit wire */
> +#define SPI_NO_RX      BIT(30)         /* no receive wire */
> +#define SPI_MODE_KERNEL_MASK   (SPI_NO_TX | SPI_NO_RX)

This needs a comment to explain what's going on with the flags (split).

-- 
With Best Regards,
Andy Shevchenko