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, 110 insertions, 0 deletions

diff --git a/Documentation/admin-guide/media/vimc.rst b/Documentation/admin-guide/media/vimc.rst
new file mode 100644
index 000000000..29d843a8d
--- /dev/null
+++ b/Documentation/admin-guide/media/vimc.rst
@@ -0,0 +1,110 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+The Virtual Media Controller Driver (vimc)
+==========================================
+
+The vimc driver emulates complex video hardware using the V4L2 API and the Media
+API. It has a capture device and three subdevices: sensor, debayer and scaler.
+
+Topology
+--------
+
+The topology is hardcoded, although you could modify it in vimc-core and
+recompile the driver to achieve your own topology. This is the default topology:
+
+.. _vimc_topology_graph:
+
+.. kernel-figure:: vimc.dot
+    :alt:   Diagram of the default media pipeline topology
+    :align: center
+
+    Media pipeline graph on vimc
+
+Configuring the topology
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Each subdevice will come with its default configuration (pixelformat, height,
+width, ...). One needs to configure the topology in order to match the
+configuration on each linked subdevice to stream frames through the pipeline.
+If the configuration doesn't match, the stream will fail. The ``v4l-utils``
+package is a bundle of user-space applications, that comes with ``media-ctl`` and
+``v4l2-ctl`` that can be used to configure the vimc configuration. This sequence
+of commands fits for the default topology:
+
+.. code-block:: bash
+
+        media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]'
+        media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]'
+        media-ctl -d platform:vimc -V '"Scaler":0[fmt:RGB888_1X24/640x480]'
+        media-ctl -d platform:vimc -V '"Scaler":0[crop:(100,50)/400x150]'
+        media-ctl -d platform:vimc -V '"Scaler":1[fmt:RGB888_1X24/300x700]'
+        v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=300,height=700
+        v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81
+
+Subdevices
+----------
+
+Subdevices define the behavior of an entity in the topology. Depending on the
+subdevice, the entity can have multiple pads of type source or sink.
+
+vimc-sensor:
+	Generates images in several formats using video test pattern generator.
+	Exposes:
+
+	* 1 Pad source
+
+vimc-lens:
+	Ancillary lens for a sensor. Supports auto focus control. Linked to
+	a vimc-sensor using an ancillary link. The lens supports FOCUS_ABSOLUTE
+	control.
+
+.. code-block:: bash
+
+	media-ctl -p
+	...
+	- entity 28: Lens A (0 pad, 0 link)
+			type V4L2 subdev subtype Lens flags 0
+			device node name /dev/v4l-subdev6
+	- entity 29: Lens B (0 pad, 0 link)
+			type V4L2 subdev subtype Lens flags 0
+			device node name /dev/v4l-subdev7
+	v4l2-ctl -d /dev/v4l-subdev7 -C focus_absolute
+	focus_absolute: 0
+
+
+vimc-debayer:
+	Transforms images in bayer format into a non-bayer format.
+	Exposes:
+
+	* 1 Pad sink
+	* 1 Pad source
+
+vimc-scaler:
+	Re-size the image to meet the source pad resolution. E.g.: if the sync
+	pad is configured to 360x480 and the source to 1280x720, the image will
+	be stretched to fit the source resolution. Works for any resolution
+	within the vimc limitations (even shrinking the image if necessary).
+	Exposes:
+
+	* 1 Pad sink
+	* 1 Pad source
+
+vimc-capture:
+	Exposes node /dev/videoX to allow userspace to capture the stream.
+	Exposes:
+
+	* 1 Pad sink
+	* 1 Pad source
+
+Module options
+--------------
+
+Vimc has a module parameter to configure the driver.
+
+* ``allocator=<unsigned int>``
+
+	memory allocator selection, default is 0. It specifies the way buffers
+	will be allocated.
+
+		- 0: vmalloc
+		- 1: dma-contig