linux-kernel - [PATCH] i2c: core: Allocate temporary client dynamically

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Message-ID: <f9aa39362e918b62aec0567f899b37d8d3c44710.1740064176.git.geert+renesas@glider.be>
Date: Thu, 20 Feb 2025 16:12:12 +0100
From: Geert Uytterhoeven <geert+renesas@...der.be>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Su Hui <suhui@...china.com>
Cc: linux-i2c@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH] i2c: core: Allocate temporary client dynamically

drivers/i2c/i2c-core-base.c: In function ‘i2c_detect.isra’:
drivers/i2c/i2c-core-base.c:2544:1: warning: the frame size of 1312 bytes is larger than 1024 bytes [-Wframe-larger-than=]
 2544 | }
      | ^

Fix this by allocating the temporary client structure dynamically, as it
is a rather large structure (1216 bytes, depending on kernel config).

Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
Mostly compile-tested, as apparently I have no I2C devices for which
driver->detect and driver->address_list are valid.

Apparently an alternative solution was posted before, but that does not
fully address the potential stack size issue:
"[PATCH] i2c: core: mark i2c_detect_address noinline_for_stack".
https://lore.kernel.org/20250210080217.2772467-1-suhui@nfschina.com
---
 drivers/i2c/i2c-core-base.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 35a221e2c11c1460..7ad1ad5c8c3f5694 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 +2527,24 @@ 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(*temp_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;
 }
 
-- 
2.43.0