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, 74 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ad7879-i2c.c b/drivers/input/touchscreen/ad7879-i2c.c
new file mode 100644
index 000000000..c1ccdf86b
--- /dev/null
+++ b/drivers/input/touchscreen/ad7879-i2c.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AD7879-1/AD7889-1 touchscreen (I2C bus)
+ *
+ * Copyright (C) 2008-2010 Michael Hennerich, Analog Devices Inc.
+ */
+
+#include <linux/input.h>	/* BUS_I2C */
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/regmap.h>
+
+#include "ad7879.h"
+
+#define AD7879_DEVID		0x79	/* AD7879-1/AD7889-1 */
+
+static const struct regmap_config ad7879_i2c_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 15,
+};
+
+static int ad7879_i2c_probe(struct i2c_client *client)
+{
+	struct regmap *regmap;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_WORD_DATA)) {
+		dev_err(&client->dev, "SMBUS Word Data not Supported\n");
+		return -EIO;
+	}
+
+	regmap = devm_regmap_init_i2c(client, &ad7879_i2c_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	return ad7879_probe(&client->dev, regmap, client->irq,
+			    BUS_I2C, AD7879_DEVID);
+}
+
+static const struct i2c_device_id ad7879_id[] = {
+	{ .name = "ad7879" },
+	{ .name = "ad7889" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ad7879_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id ad7879_i2c_dt_ids[] = {
+	{ .compatible = "adi,ad7879-1", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad7879_i2c_dt_ids);
+#endif
+
+static struct i2c_driver ad7879_i2c_driver = {
+	.driver = {
+		.name		= "ad7879",
+		.dev_groups	= ad7879_groups,
+		.pm		= &ad7879_pm_ops,
+		.of_match_table	= of_match_ptr(ad7879_i2c_dt_ids),
+	},
+	.probe		= ad7879_i2c_probe,
+	.id_table	= ad7879_id,
+};
+
+module_i2c_driver(ad7879_i2c_driver);
+
+MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
+MODULE_DESCRIPTION("AD7879(-1) touchscreen I2C bus driver");
+MODULE_LICENSE("GPL");