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    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@c-s.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@c-s.fr>
    Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
    Signed-off-by: Ben Hutchings <ben@decadent.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;
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