Re: [PATCH v8 03/10] HID: asus: fortify keyboard handshake

[Denis Benato <benato.denis96@gmail.com>]

On 11/1/25 11:47, Antheas Kapenekakis wrote:
> Handshaking with an Asus device involves sending it a feature report
> with the string "ASUS Tech.Inc." and then reading it back to verify the
> handshake was successful, under the feature ID the interaction will
> take place.
>
> Currently, the driver only does the first part. Add the readback to
> verify the handshake was successful. As this could cause breakages,
> allow the verification to fail with a dmesg error until we verify
> all devices work with it (they seem to).
>
> Since the response is more than 16 bytes, increase the buffer size
> to 64 as well to avoid overflow errors.
>
> Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
> ---
>  drivers/hid/hid-asus.c | 32 +++++++++++++++++++++++++++++---
>  1 file changed, 29 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hid/hid-asus.c b/drivers/hid/hid-asus.c
> index 4676b7f20caf..03f0d86936fc 100644
> --- a/drivers/hid/hid-asus.c
> +++ b/drivers/hid/hid-asus.c
> @@ -48,7 +48,7 @@ MODULE_DESCRIPTION("Asus HID Keyboard and TouchPad");
>  #define FEATURE_REPORT_ID 0x0d
>  #define INPUT_REPORT_ID 0x5d
>  #define FEATURE_KBD_REPORT_ID 0x5a
> -#define FEATURE_KBD_REPORT_SIZE 16
> +#define FEATURE_KBD_REPORT_SIZE 64
>  #define FEATURE_KBD_LED_REPORT_ID1 0x5d
>  #define FEATURE_KBD_LED_REPORT_ID2 0x5e
>  
> @@ -393,14 +393,40 @@ static int asus_kbd_set_report(struct hid_device *hdev, const u8 *buf, size_t bu
>  
>  static int asus_kbd_init(struct hid_device *hdev, u8 report_id)
>  {
> +	/*
> +	 * The handshake is first sent as a set_report, then retrieved
> +	 * from a get_report. They should be equal.
> +	 */
>  	const u8 buf[] = { report_id, 0x41, 0x53, 0x55, 0x53, 0x20, 0x54,
>  		     0x65, 0x63, 0x68, 0x2e, 0x49, 0x6e, 0x63, 0x2e, 0x00 };
> +	u8 *readbuf;

__free(kfree) = NULL here? Would simplify the code.

>  	int ret;
>  
>  	ret = asus_kbd_set_report(hdev, buf, sizeof(buf));
> -	if (ret < 0)
> -		hid_err(hdev, "Asus failed to send init command: %d\n", ret);
> +	if (ret < 0) {
> +		hid_err(hdev, "Asus failed to send handshake: %d\n", ret);
> +		return ret;
> +	}
> +
> +	readbuf = kzalloc(FEATURE_KBD_REPORT_SIZE, GFP_KERNEL);
> +	if (!readbuf)
> +		return -ENOMEM;
> +
> +	ret = hid_hw_raw_request(hdev, report_id, readbuf,
> +				 FEATURE_KBD_REPORT_SIZE, HID_FEATURE_REPORT,
> +				 HID_REQ_GET_REPORT);
See comments on patch 1 (also reported below): not sure if others
report_id are going to answer, my guess is that we will have to try
if you choose to go that route.
> +	if (ret < 0) {
> +		hid_err(hdev, "Asus failed to receive handshake ack: %d\n", ret);
> +	} else if (memcmp(readbuf, buf, sizeof(buf)) != 0) {
> +		hid_warn(hdev, "Asus handshake returned invalid response: %*ph\n",
> +			FEATURE_KBD_REPORT_SIZE, readbuf);
> +		/*
> +		 * Do not return error if handshake is wrong until this is
> +		 * verified to work for all devices.
> +		 */
In review of patch 1 I requested this function to be called with more report_id
than just 0x5a so this will have to be checked against those values too.

In alternative you can fork based on the report_id, but having confirmation that
this is valid with those ids too would be of great help. Perhaps I can help you
with this asking to asus-linux users.
> +	}
>  
> +	kfree(readbuf);
>  	return ret;
>  }
>