[PATCH v2 1/4] spi: spidev: Restore all SPI mode flags on ioctl failure

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

From: Geert Uytterhoeven <geert+renesas@xxxxxxxxxxxxxx>

In commit f477b7fb13df2b843997559ff34e87d054ba6538 ("spi: DUAL and QUAD
support"), spi_device.mode was enlarged from 8 to 16 bits.

However, the spidev code still only saved 8 bits of data. If a spidev
SPI_IOC_WR_MODE or SPI_IOC_WR_LSB_FIRST request failed, only the lower 8
bits of the SPI mode were restored, inadvertently clearing the upper 8
bits, possibly disabling Quad or Dual SPI transfers for the device.

Save up to 32 bits to fix this.

For SPI_IOC_WR_MODE this is probably not so important, as it doesn't allow
setting Quad or Dual mode anyway, but SPI_IOC_WR_LSB_FIRST is used to just
set or clear a single bit.

Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxxxxxxx>
---
v2:
  - Split off from "spi: spidev: Add support for Dual/Quad SPI Transfers",
    as this is a bug fix.
    Mark, do you think this is worthwhile for stable (v3.12 and v3.13)?

 drivers/spi/spidev.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index d7c6e36021e8..2abc0f5a82be 100644
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -374,7 +374,7 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case SPI_IOC_WR_MODE:
 		retval = __get_user(tmp, (u8 __user *)arg);
 		if (retval == 0) {
-			u8	save = spi->mode;
+			u32	save = spi->mode;
 
 			if (tmp & ~SPI_MODE_MASK) {
 				retval = -EINVAL;
@@ -393,7 +393,7 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case SPI_IOC_WR_LSB_FIRST:
 		retval = __get_user(tmp, (__u8 __user *)arg);
 		if (retval == 0) {
-			u8	save = spi->mode;
+			u32	save = spi->mode;
 
 			if (tmp)
 				spi->mode |= SPI_LSB_FIRST;
-- 
1.7.9.5

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