[PATCH] i2c: core: Allocate temporary client dynamically

Geert Uytterhoeven
2025-02-20T15:12:21Z

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@glider.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