linux-kernel - [PATCH] Revert "i2c: core: Allocate temp client on the stack in i2c

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Message-Id: <20250221205449.3838714-1-arnd@kernel.org>
Date: Fri, 21 Feb 2025 21:54:40 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Heiner Kallweit <hkallweit1@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Andi Shyti <andi.shyti@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Joe Hattori <joe@...is.s.u-tokyo.ac.jp>,
	Uwe Kleine-König <u.kleine-koenig@...libre.com>,
	Hans de Goede <hdegoede@...hat.com>,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] Revert "i2c: core: Allocate temp client on the stack in i2c_detect"

From: Arnd Bergmann <arnd@...db.de>

struct i2c_client is way too large to be put on the kernel stack, and depending
on the kernel configuration, this can exceed the compile-time warning limit:

drivers/i2c/i2c-core-base.c:1420:12: error: stack frame size (1040) exceeds limit (1024) in 'i2c_do_add_adapter' [-Werror,-Wframe-larger-than]
 1420 | static int i2c_do_add_adapter(struct i2c_driver *driver,
      |            ^

The current version is the result of a cleanup patch that does not appear
to be a requirement for anything else, so address the problem through a
simple revert.

Fixes: 735668f8e5c9 ("i2c: core: Allocate temp client on the stack in i2c_detect")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/i2c/i2c-core-base.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 35a221e2c11c..5c9419e95044 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2506,7 +2506,7 @@ static int i2c_detect_address(struct i2c_client *temp_client,
 static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
 {
 	const unsigned short *address_list;
-	struct i2c_client temp_client;
+	struct i2c_client *temp_client;
 	int i, err = 0;
 
 	address_list = driver->address_list;
@@ -2527,19 +2527,22 @@ static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
 		return 0;
 
 	/* Set up a temporary client to help detect callback */
-	memset(&temp_client, 0, sizeof(temp_client));
-	temp_client.adapter = adapter;
+	temp_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
+	if (!temp_client)
+		return -ENOMEM;
+	temp_client->adapter = adapter;
 
 	for (i = 0; address_list[i] != I2C_CLIENT_END; i += 1) {
 		dev_dbg(&adapter->dev,
 			"found normal entry for adapter %d, addr 0x%02x\n",
 			i2c_adapter_id(adapter), address_list[i]);
-		temp_client.addr = address_list[i];
-		err = i2c_detect_address(&temp_client, driver);
+		temp_client->addr = address_list[i];
+		err = i2c_detect_address(temp_client, driver);
 		if (unlikely(err))
 			break;
 	}
 
+	kfree(temp_client);
 	return err;
 }
 
-- 
2.39.5