spi: spidev: mask SPI_CS_HIGH in SPI_IOC_RD_MODE

[ Upstream commit 7dbfa445ff7393d1c4c066c1727c9e0af1251958 ]

Commit f3186dd87669 ("spi: Optionally use GPIO descriptors for CS GPIOs")
has changed the user-space interface so that bogus SPI_CS_HIGH started
to appear in the mask returned by SPI_IOC_RD_MODE even for active-low CS
pins. Commit 138c9c32f090
("spi: spidev: Fix CS polarity if GPIO descriptors are used") fixed only
SPI_IOC_WR_MODE part of the problem. Let's fix SPI_IOC_RD_MODE
symmetrically.

Test case:

	#include <sys/ioctl.h>
	#include <fcntl.h>
	#include <linux/spi/spidev.h>

	int main(int argc, char **argv)
	{
		char modew = SPI_CPHA;
		char moder;
		int f = open("/dev/spidev0.0", O_RDWR);

		if (f < 0)
			return 1;

		ioctl(f, SPI_IOC_WR_MODE, &modew);
		ioctl(f, SPI_IOC_RD_MODE, &moder);

		return moder == modew ? 0 : 2;
	}

Fixes: f3186dd87669 ("spi: Optionally use GPIO descriptors for CS GPIOs")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Link: https://lore.kernel.org/r/20221130162927.539512-1-alexander.sverdlin@siemens.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index 1bd73e3..d233e24 100644 (file)
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -376,12 +376,23 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
        switch (cmd) {
        /* read requests */
        case SPI_IOC_RD_MODE:
-               retval = put_user(spi->mode & SPI_MODE_MASK,
-                                       (__u8 __user *)arg);
-               break;
        case SPI_IOC_RD_MODE32:
-               retval = put_user(spi->mode & SPI_MODE_MASK,
-                                       (__u32 __user *)arg);
+               tmp = spi->mode;
+
+               {
+                       struct spi_controller *ctlr = spi->controller;
+
+                       if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
+                           ctlr->cs_gpiods[spi->chip_select])
+                               tmp &= ~SPI_CS_HIGH;
+               }
+
+               if (cmd == SPI_IOC_RD_MODE)
+                       retval = put_user(tmp & SPI_MODE_MASK,
+                                         (__u8 __user *)arg);
+               else
+                       retval = put_user(tmp & SPI_MODE_MASK,
+                                         (__u32 __user *)arg);
                break;
        case SPI_IOC_RD_LSB_FIRST:
                retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,