Re: [PATCH] i2c: core: Allocate temporary client dynamically

Su Hui
2025-02-21T01:55:52Z

On 2025/2/20 23:12, Geert Uytterhoeven wrote:
> 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;
> }

Looks good to me.

Reviewed-by: Su Hui <suhui@nfschina.com>

Su Hui