x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 121 insertions, 0 deletions

diff --git a/include/acpi/video.h b/include/acpi/video.h
new file mode 100644
index 000000000..044c46313
--- /dev/null
+++ b/include/acpi/video.h
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ACPI_VIDEO_H
+#define __ACPI_VIDEO_H
+
+#include <linux/errno.h> /* for ENODEV */
+#include <linux/types.h> /* for bool */
+
+struct acpi_video_brightness_flags {
+	u8 _BCL_no_ac_battery_levels:1;	/* no AC/Battery levels in _BCL */
+	u8 _BCL_reversed:1;		/* _BCL package is in a reversed order */
+	u8 _BQC_use_index:1;		/* _BQC returns an index value */
+};
+
+struct acpi_video_device_brightness {
+	int curr;
+	int count;
+	int *levels;
+	struct acpi_video_brightness_flags flags;
+};
+
+struct acpi_device;
+
+#define ACPI_VIDEO_CLASS	"video"
+
+#define ACPI_VIDEO_DISPLAY_CRT  1
+#define ACPI_VIDEO_DISPLAY_TV   2
+#define ACPI_VIDEO_DISPLAY_DVI  3
+#define ACPI_VIDEO_DISPLAY_LCD  4
+
+#define ACPI_VIDEO_DISPLAY_LEGACY_MONITOR 0x0100
+#define ACPI_VIDEO_DISPLAY_LEGACY_PANEL   0x0110
+#define ACPI_VIDEO_DISPLAY_LEGACY_TV      0x0200
+
+#define ACPI_VIDEO_NOTIFY_SWITCH		0x80
+#define ACPI_VIDEO_NOTIFY_PROBE			0x81
+#define ACPI_VIDEO_NOTIFY_CYCLE			0x82
+#define ACPI_VIDEO_NOTIFY_NEXT_OUTPUT		0x83
+#define ACPI_VIDEO_NOTIFY_PREV_OUTPUT		0x84
+#define ACPI_VIDEO_NOTIFY_CYCLE_BRIGHTNESS	0x85
+#define ACPI_VIDEO_NOTIFY_INC_BRIGHTNESS	0x86
+#define ACPI_VIDEO_NOTIFY_DEC_BRIGHTNESS	0x87
+#define ACPI_VIDEO_NOTIFY_ZERO_BRIGHTNESS	0x88
+#define ACPI_VIDEO_NOTIFY_DISPLAY_OFF		0x89
+
+enum acpi_backlight_type {
+	acpi_backlight_undef = -1,
+	acpi_backlight_none = 0,
+	acpi_backlight_video,
+	acpi_backlight_vendor,
+	acpi_backlight_native,
+	acpi_backlight_nvidia_wmi_ec,
+	acpi_backlight_apple_gmux,
+	acpi_backlight_dell_uart,
+};
+
+#if IS_ENABLED(CONFIG_ACPI_VIDEO)
+extern int acpi_video_register(void);
+extern void acpi_video_unregister(void);
+extern void acpi_video_register_backlight(void);
+extern int acpi_video_get_edid(struct acpi_device *device, int type,
+			       int device_id, void **edid);
+/*
+ * Note: The value returned by acpi_video_handles_brightness_key_presses()
+ * may change over time and should not be cached.
+ */
+extern bool acpi_video_handles_brightness_key_presses(void);
+extern int acpi_video_get_levels(struct acpi_device *device,
+				 struct acpi_video_device_brightness **dev_br,
+				 int *pmax_level);
+
+extern enum acpi_backlight_type __acpi_video_get_backlight_type(bool native,
+								bool *auto_detect);
+
+static inline enum acpi_backlight_type acpi_video_get_backlight_type(void)
+{
+	return __acpi_video_get_backlight_type(false, NULL);
+}
+
+/*
+ * This function MUST only be called by GPU drivers to check if the driver
+ * should register a backlight class device. This function not only checks
+ * if a GPU native backlight device should be registered it *also* tells
+ * the ACPI video-detect code that native GPU backlight control is available.
+ * Therefor calling this from any place other then the GPU driver is wrong!
+ * To check if GPU native backlight control is used in other places instead use:
+ *   if (acpi_video_get_backlight_type() == acpi_backlight_native) { ... }
+ */
+static inline bool acpi_video_backlight_use_native(void)
+{
+	return __acpi_video_get_backlight_type(true, NULL) == acpi_backlight_native;
+}
+#else
+static inline int acpi_video_register(void) { return -ENODEV; }
+static inline void acpi_video_unregister(void) { return; }
+static inline void acpi_video_register_backlight(void) { return; }
+static inline int acpi_video_get_edid(struct acpi_device *device, int type,
+				      int device_id, void **edid)
+{
+	return -ENODEV;
+}
+static inline enum acpi_backlight_type acpi_video_get_backlight_type(void)
+{
+	return acpi_backlight_vendor;
+}
+static inline bool acpi_video_backlight_use_native(void)
+{
+	return true;
+}
+static inline bool acpi_video_handles_brightness_key_presses(void)
+{
+	return false;
+}
+static inline int acpi_video_get_levels(struct acpi_device *device,
+			struct acpi_video_device_brightness **dev_br,
+			int *pmax_level)
+{
+	return -ENODEV;
+}
+#endif
+
+#endif