5.15-stable review patch. If anyone has any objections, please let me know.
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From: Kent Gibson warthog618@gmail.com
commit b440396387418fe2feaacd41ca16080e7a8bc9ad upstream.
linereq_set_config() behaves badly when direction is not set. The configuration validation is borrowed from linereq_create(), where, to verify the intent of the user, the direction must be set to in order to effect a change to the electrical configuration of a line. But, when applied to reconfiguration, that validation does not allow for the unset direction case, making it possible to clear flags set previously without specifying the line direction.
Adding to the inconsistency, those changes are not immediately applied by linereq_set_config(), but will take effect when the line value is next get or set.
For example, by requesting a configuration with no flags set, an output line with GPIO_V2_LINE_FLAG_ACTIVE_LOW and GPIO_V2_LINE_FLAG_OPEN_DRAIN set could have those flags cleared, inverting the sense of the line and changing the line drive to push-pull on the next line value set.
Skip the reconfiguration of lines for which the direction is not set, and only reconfigure the lines for which direction is set.
Fixes: a54756cb24ea ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL") Signed-off-by: Kent Gibson warthog618@gmail.com Link: https://lore.kernel.org/r/20240626052925.174272-3-warthog618@gmail.com Signed-off-by: Bartosz Golaszewski bartosz.golaszewski@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpio/gpiolib-cdev.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
--- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -1186,15 +1186,18 @@ static long linereq_set_config_unlocked( for (i = 0; i < lr->num_lines; i++) { desc = lr->lines[i].desc; flags = gpio_v2_line_config_flags(lc, i); + /* + * Lines not explicitly reconfigured as input or output + * are left unchanged. + */ + if (!(flags & GPIO_V2_LINE_DIRECTION_FLAGS)) + continue; + polarity_change = (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) != ((flags & GPIO_V2_LINE_FLAG_ACTIVE_LOW) != 0));
gpio_v2_line_config_flags_to_desc_flags(flags, &desc->flags); - /* - * Lines have to be requested explicitly for input - * or output, else the line will be treated "as is". - */ if (flags & GPIO_V2_LINE_FLAG_OUTPUT) { int val = gpio_v2_line_config_output_value(lc, i);
@@ -1202,7 +1205,7 @@ static long linereq_set_config_unlocked( ret = gpiod_direction_output(desc, val); if (ret) return ret; - } else if (flags & GPIO_V2_LINE_FLAG_INPUT) { + } else { ret = gpiod_direction_input(desc); if (ret) return ret;