Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20201106150706.29089-1-TheSven73@gmail.com>
In-Reply-To: <20201106150706.29089-1-TheSven73@gmail.com>
From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Mon, 9 Nov 2020 16:25:10 +0200
Message-ID: <CAHp75VfP1R7bXV6nWWnovWB5BMFcNNEmwBQXheBCUVDbr=xXGA@mail.gmail.com>
Subject: Re: [PATCH v1] spi: fix client driver breakages when using GPIO descriptors
To:     Sven Van Asbroeck <thesven73@gmail.com>
Cc:     Mark Brown <broonie@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Jonathan Cameron <jonathan.cameron@huawei.com>,
        Simon Han <z.han@kunbus.com>, Lukas Wunner <lukas@wunner.de>,
        linux-spi <linux-spi@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Nov 6, 2020 at 5:08 PM Sven Van Asbroeck <thesven73@gmail.com> wrote:
>
> From: Sven Van Asbroeck <thesven73@gmail.com>
>
> Commit f3186dd87669 ("spi: Optionally use GPIO descriptors for CS GPIOs")
> introduced the optional use of GPIO descriptors for chip selects.
>
> A side-effect of this change: when a SPI bus uses GPIO descriptors,
> all its client devices have SPI_CS_HIGH set in spi->mode. This flag is
> required for the SPI bus to operate correctly.
>
> This unfortunately breaks many client drivers, which use the following
> pattern to configure their underlying SPI bus:
>
> static int client_device_probe(struct spi_device *spi)
> {
>         ...
>         spi->mode = SPI_MODE_0;
>         spi->bits_per_word = 8;
>         err = spi_setup(spi);
>         ..
> }
>
> In short, many client drivers overwrite the SPI_CS_HIGH bit in
> spi->mode, and break the underlying SPI bus driver.

Sounds like "many SPI drivers have to be fixed".


-- 
With Best Regards,
Andy Shevchenko