Commit 624a989d authored Nov 30, 2022 by Alexander Sverdlin Committed by Greg Kroah-Hartman Jan 18, 2023

spi: spidev: mask SPI_CS_HIGH in SPI_IOC_RD_MODE



[ Upstream commit 7dbfa445ff7393d1c4c066c1727c9e0af1251958 ]

Commit f3186dd8 ("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: f3186dd8 ("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>

parent 52fb0ffe

drivers/spi/spidev.c

+16 −5

Original line number	Diff line number	Diff line
		@@ -373,11 +373,22 @@ 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,
		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: