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Date:   Fri, 22 May 2020 17:29:01 +0100
From:   Mark Brown <broonie@kernel.org>
To:     dillon min <dillon.minfei@gmail.com>
Cc:     Rob Herring <robh+dt@kernel.org>, p.zabel@pengutronix.de,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        thierry.reding@gmail.com, Sam Ravnborg <sam@ravnborg.org>,
        Dave Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
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        "open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
        linux-clk <linux-clk@vger.kernel.org>
Subject: Re: [PATCH v4 3/8] spi: stm32: Add 'SPI_SIMPLEX_RX', 'SPI_3WIRE_RX'
 support for stm32f4
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On Fri, May 22, 2020 at 11:59:25PM +0800, dillon min wrote:

> but, after spi-core create a dummy tx_buf or rx_buf, then i can't get
> the correct spi_3wire direction.
> actually, this dummy tx_buf is useless for SPI_3WIRE. it's has meaning
> for SPI_SIMPLE_RX mode,
> simulate SPI_FULL_DUMPLEX

Oh, that's annoying.  I think the fix here is in the core, it should
ignore MUST_TX and MUST_RX in 3WIRE mode since they clearly make no
sense there.

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