linux-kernel - [PATCH 17/18] spi: stm32: properly handle 0 byte transfer

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Date:   Wed, 5 Aug 2020 09:02:12 +0200
From:   Alain Volmat <alain.volmat@...com>
To:     <broonie@...nel.org>, <amelie.delaunay@...com>
CC:     <mcoquelin.stm32@...il.com>, <alexandre.torgue@...com>,
        <linux-spi@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <fabrice.gasnier@...com>,
        <alain.volmat@...com>
Subject: [PATCH 17/18] spi: stm32: properly handle 0 byte transfer

On 0 byte transfer request, return straight from the
xfer function after finalizing the transfer.

Signed-off-by: Alain Volmat <alain.volmat@...com>
---
 drivers/spi/spi-stm32.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
index 177f82700de0..b909afd9e99b 100644
--- a/drivers/spi/spi-stm32.c
+++ b/drivers/spi/spi-stm32.c
@@ -1658,6 +1658,12 @@ static int stm32_spi_transfer_one(struct spi_master *master,
 	unsigned long timeout;
 	int ret;
 
+	/* Don't do anything on 0 bytes transfers */
+	if (transfer->len == 0) {
+		spi->xfer_status = 0;
+		goto finalize;
+	}
+
 	spi->tx_buf = transfer->tx_buf;
 	spi->rx_buf = transfer->rx_buf;
 	spi->tx_len = spi->tx_buf ? transfer->len : 0;
@@ -1702,6 +1708,7 @@ static int stm32_spi_transfer_one(struct spi_master *master,
 
 	spi->cfg->disable(spi);
 
+finalize:
 	spi_finalize_current_transfer(master);
 
 	return spi->xfer_status;
-- 
2.7.4