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, 55 insertions, 0 deletions

diff --git a/Documentation/input/notifier.rst b/Documentation/input/notifier.rst
new file mode 100644
index 000000000..824379399
--- /dev/null
+++ b/Documentation/input/notifier.rst
@@ -0,0 +1,55 @@
+=================
+Keyboard notifier
+=================
+
+One can use register_keyboard_notifier to get called back on keyboard
+events (see kbd_keycode() function for details).  The passed structure is
+keyboard_notifier_param (see <linux/keyboard.h>):
+
+- 'vc' always provide the VC for which the keyboard event applies;
+- 'down' is 1 for a key press event, 0 for a key release;
+- 'shift' is the current modifier state, mask bit indexes are KG_*;
+- 'ledstate' is the current LED state;
+- 'value' depends on the type of event.
+
+- KBD_KEYCODE events are always sent before other events, value is the keycode.
+- KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym.
+  value is the keycode.
+- KBD_UNICODE events are sent if the keycode -> keysym translation produced a
+  unicode character. value is the unicode value.
+- KBD_KEYSYM events are sent if the keycode -> keysym translation produced a
+  non-unicode character. value is the keysym.
+- KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms.
+  That permits one to inspect the resulting LEDs for instance.
+
+For each kind of event but the last, the callback may return NOTIFY_STOP in
+order to "eat" the event: the notify loop is stopped and the keyboard event is
+dropped.
+
+In a rough C snippet, we have::
+
+    kbd_keycode(keycode) {
+	...
+	params.value = keycode;
+	if (notifier_call_chain(KBD_KEYCODE,&params) == NOTIFY_STOP)
+	    || !bound) {
+		notifier_call_chain(KBD_UNBOUND_KEYCODE,&params);
+		return;
+	}
+
+	if (unicode) {
+		param.value = unicode;
+		if (notifier_call_chain(KBD_UNICODE,&params) == NOTIFY_STOP)
+			return;
+		emit unicode;
+		return;
+	}
+
+	params.value = keysym;
+	if (notifier_call_chain(KBD_KEYSYM,&params) == NOTIFY_STOP)
+		return;
+	apply keysym;
+	notifier_call_chain(KBD_POST_KEYSYM,&params);
+    }
+
+.. note:: This notifier is usually called from interrupt context.