[PATCH] spi: spidev: Fix for reverting spi max speed value only on failure

[PATCH] spi: spidev: Fix for reverting spi max speed value only on failure

[Vivek Pernamitta]

When user space application request for change in spi clock
using ioctl, current value is taken back-up and new value is
assigned to spi->max_speed_hz, then spi_setup() function is
called with new value. If spi_setup() function fails, it needs
reverting to old spi_max_speed value only in failure condition.

Signed-off-by: Vivek Pernamitta <pervivek@gmail.com>
---
 drivers/spi/spidev.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index 30498cf25f3b..70382b642f37 100644
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -458,9 +458,10 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			retval = spi_setup(spi);
 			if (retval >= 0)
 				spidev->speed_hz = tmp;
-			else
+			else {
 				dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
-			spi->max_speed_hz = save;
+				spi->max_speed_hz = save;
+			}
 		}
 		break;
 
-- 
2.17.1

Re: [PATCH] spi: spidev: Fix for reverting spi max speed value only on failure

[Mark Brown]

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On Sun, Jun 02, 2019 at 07:49:59PM +0530, Vivek Pernamitta wrote:
> When user space application request for change in spi clock
> using ioctl, current value is taken back-up and new value is
> assigned to spi->max_speed_hz, then spi_setup() function is
> called with new value. If spi_setup() function fails, it needs
> reverting to old spi_max_speed value only in failure condition.

The current behaviour is intentional, we're not modifying max_speed_hz
so we can continue to enforce the kernel limit no matter what userspace
asked for - actually looking at the code we should probably have an
explicit error check in there to reject attempts to raise it here, not
sure why we're not doing that already.

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