[PATCH] gpiolib: reset lookup flags for each hogged line

[PATCH] gpiolib: reset lookup flags for each hogged line

[Jinseob Kim]

gpiochip_add_hog() initializes lflags once before iterating over the GPIO
specifiers. In the non-OF path, an active-low line sets GPIO_ACTIVE_LOW,
but a later active-high line does not clear it. A single firmware hog
with mixed polarities therefore configures later active-high lines as
active-low, including inverting their initial output value.

Initialize the lookup flags for each line before translating its flags.
The OF helper already overwrites the flags for each specifier; the
non-OF path must also start with a fresh value.

Add a KUnit case using one software-node hog with four alternating line
polarities. Check both the descriptor polarity and raw output level for
a logical high using the existing software GPIO provider. On UML, the
eight existing cases pass before the fix while the new case fails;
all nine cases pass after the fix with the same configuration.

Clang W=1 and private Sparse C=2 builds of both changed files complete
without diagnostics. No physical GPIO hardware was tested.

Codex assisted with the source analysis, fix, regression test and commit
message.

Fixes: 802c51a83e9a ("gpiolib: fix hogs with multiple lines")
Signed-off-by: Jinseob Kim <kimjinseob88@gmail.com>
---
Target: brgl/linux gpio/for-current at 9e4b35c95fede87bad36f68b7ff1eae94ea6b910.
Tool use: Codex assisted a bounded review of public kernel code, the
minimal fix, test and description. The task requested a reproducible
general functional bug fix, not a fuzzing or security campaign.
Testing: actual before/after UML KUnit and Clang/private Sparse builds.
Physical GPIO hardware was not tested.

 drivers/gpio/gpiolib-kunit.c | 88 ++++++++++++++++++++++++++++++++++++
 drivers/gpio/gpiolib.c       |  3 +-
 2 files changed, 90 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib-kunit.c b/drivers/gpio/gpiolib-kunit.c
index f005854e7f..01205acf62 100644
--- a/drivers/gpio/gpiolib-kunit.c
+++ b/drivers/gpio/gpiolib-kunit.c
@@ -862,11 +862,99 @@ static struct kunit_suite gpio_swnode_hog_test_suite = {
 	.init = gpio_swnode_register_drivers,
 };
 
+/* A single non-OF hog may describe lines with different polarities. */
+static const struct software_node gpio_mixed_hog_provider_swnode = {
+	.name = "gpio-mixed-hog-provider",
+};
+
+static const u32 gpio_mixed_hog_gpios[] = {
+	0, GPIO_ACTIVE_LOW,
+	1, GPIO_ACTIVE_HIGH,
+	2, GPIO_ACTIVE_LOW,
+	3, GPIO_ACTIVE_HIGH,
+};
+
+static const struct property_entry gpio_mixed_hog_properties[] = {
+	PROPERTY_ENTRY_U32_ARRAY("gpios", gpio_mixed_hog_gpios),
+	PROPERTY_ENTRY_BOOL("output-high"),
+	PROPERTY_ENTRY_BOOL("gpio-hog"),
+	{ }
+};
+
+static const struct software_node gpio_mixed_hog_swnode =
+	SOFTWARE_NODE("mixed-hog", gpio_mixed_hog_properties,
+		      &gpio_mixed_hog_provider_swnode);
+
+static const struct software_node *const gpio_mixed_hog_swnodes[] = {
+	&gpio_mixed_hog_provider_swnode,
+	&gpio_mixed_hog_swnode,
+	NULL
+};
+
+static void gpio_hog_mixed_polarities(struct kunit *test)
+{
+	struct platform_device_info pdevinfo = {
+		.name = GPIO_TEST_PROVIDER,
+		.id = PLATFORM_DEVID_NONE,
+		.fwnode = software_node_fwnode(&gpio_mixed_hog_provider_swnode),
+	};
+	struct platform_device *pdev;
+	struct gpio_device *gdev;
+	struct gpio_desc *desc;
+	bool active_low;
+	int ret;
+
+	pdev = kunit_platform_device_register_full(test, &pdevinfo);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+
+	wait_for_device_probe();
+
+	gdev = gpio_device_find_by_label(GPIO_CONSUMER_NAME);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, gdev);
+
+	ret = kunit_add_action_or_reset(test, gpio_device_put_wrapper, gdev);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	for (unsigned int i = 0; i < GPIO_TEST_PROVIDER_NGPIO; i++) {
+		desc = gpio_device_get_desc(gdev, i);
+		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, desc);
+
+		active_low = gpio_mixed_hog_gpios[i * 2 + 1] == GPIO_ACTIVE_LOW;
+		KUNIT_EXPECT_EQ(test, gpiod_is_active_low(desc), active_low);
+		/* A logical high must drive the inverse level on active-low lines. */
+		KUNIT_EXPECT_EQ(test, gpiod_get_raw_value_cansleep(desc), !active_low);
+	}
+}
+
+static int gpio_mixed_hog_suite_init(struct kunit_suite *suite)
+{
+	return software_node_register_node_group(gpio_mixed_hog_swnodes);
+}
+
+static void gpio_mixed_hog_suite_exit(struct kunit_suite *suite)
+{
+	software_node_unregister_node_group(gpio_mixed_hog_swnodes);
+}
+
+static struct kunit_case gpio_mixed_hog_tests[] = {
+	KUNIT_CASE(gpio_hog_mixed_polarities),
+	{ }
+};
+
+static struct kunit_suite gpio_mixed_hog_test_suite = {
+	.name = "gpio-mixed-hog-polarity",
+	.test_cases = gpio_mixed_hog_tests,
+	.suite_init = gpio_mixed_hog_suite_init,
+	.suite_exit = gpio_mixed_hog_suite_exit,
+	.init = gpio_swnode_register_drivers,
+};
+
 kunit_test_suites(
 	&gpio_swnode_lookup_test_suite,
 	&gpio_swnode_probe_order_test_suite,
 	&gpio_unbind_with_consumers_test_suite,
 	&gpio_swnode_hog_test_suite,
+	&gpio_mixed_hog_test_suite,
 );
 
 MODULE_DESCRIPTION("Test module for the GPIO subsystem");
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index fbdeda2f27..db613770dc 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -975,7 +975,6 @@ int gpiochip_add_hog(struct gpio_chip *gc, struct fwnode_handle *fwnode)
 	 */
 	u32 cells = 2;
 
-	lflags = GPIO_LOOKUP_FLAGS_DEFAULT;
 	dflags = GPIOD_ASIS;
 	name = NULL;
 
@@ -1014,6 +1013,8 @@ int gpiochip_add_hog(struct gpio_chip *gc, struct fwnode_handle *fwnode)
 	fwnode_property_read_string(fwnode, "line-name", &name);
 
 	for (unsigned int i = 0; i < num_hogs; i++) {
+		lflags = GPIO_LOOKUP_FLAGS_DEFAULT;
+
 		if (is_of_node(fwnode)) {
 			/*
 			 * OF-nodes need some additional special handling for

base-commit: 9e4b35c95fede87bad36f68b7ff1eae94ea6b910