linux-kernel - [PATCH 3.16 303/305] gpio: max7301: fix driver for use with CONFIG_VMAP

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Message-ID: <lsq.1549201508.755792867@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Christophe Leroy" <christophe.leroy@....fr>,
        "Linus Walleij" <linus.walleij@...aro.org>
Subject: [PATCH 3.16 303/305] gpio: max7301: fix driver for use with
 CONFIG_VMAP_STACK

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Christophe Leroy <christophe.leroy@....fr>

commit abf221d2f51b8ce7b9959a8953f880a8b0a1400d upstream.

spi_read() and spi_write() require DMA-safe memory. When
CONFIG_VMAP_STACK is selected, those functions cannot be used
with buffers on stack.

This patch replaces calls to spi_read() and spi_write() by
spi_write_then_read() which doesn't require DMA-safe buffers.

Fixes: 0c36ec314735 ("gpio: gpio driver for max7301 SPI GPIO expander")
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpio/gpio-max7301.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

--- a/drivers/gpio/gpio-max7301.c
+++ b/drivers/gpio/gpio-max7301.c
@@ -25,7 +25,7 @@ static int max7301_spi_write(struct devi
 	struct spi_device *spi = to_spi_device(dev);
 	u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
 
-	return spi_write(spi, (const u8 *)&word, sizeof(word));
+	return spi_write_then_read(spi, &word, sizeof(word), NULL, 0);
 }
 
 /* A read from the MAX7301 means two transfers; here, one message each */
@@ -37,14 +37,8 @@ static int max7301_spi_read(struct devic
 	struct spi_device *spi = to_spi_device(dev);
 
 	word = 0x8000 | (reg << 8);
-	ret = spi_write(spi, (const u8 *)&word, sizeof(word));
-	if (ret)
-		return ret;
-	/*
-	 * This relies on the fact, that a transfer with NULL tx_buf shifts out
-	 * zero bytes (=NOOP for MAX7301)
-	 */
-	ret = spi_read(spi, (u8 *)&word, sizeof(word));
+	ret = spi_write_then_read(spi, &word, sizeof(word), &word,
+				  sizeof(word));
 	if (ret)
 		return ret;
 	return word & 0xff;