Re: [PATCH v9 04/11] HID: asus: fortify keyboard handshake

Ilpo Järvinen
2025-11-20T16:41:22Z

On Thu, 20 Nov 2025, Antheas Kapenekakis wrote:

> On Thu, 20 Nov 2025 at 15:15, Denis Benato <benato.denis96@gmail.com> wrote:
> >
> >
> > On 11/20/25 10:46, 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 6de402d215d0..5149dc7edfc5 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
> > >
> > > @@ -394,14 +394,40 @@ 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;
> > > 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);
> > I see my suggestion to use __free here didn't materialize in code using
> > it even after Ilpo kindly wrote how to correctly use it.
> >
> > I think you can move the readbuf assignment right below buf and
> > take into account what Ilpo said.
> >
> > I don't expect new variables will be added here ever again,

It's also about always doing the right thing so others will pick up the
pattern (for the cases when it's needed).

> > but I agree with Ilpo that it's a good idea here to write code
> > accounting for that possibility.
> >
> > It is my understanding that who proposes patches is expected to
> > resolve discussions when changes are proposed or to take into
> > account requested changes and submit a modified version.
>
> It was ambiguous. I interpreted Ilpo's email as a dismissal

I tried to explain how to use it, not to suggest cleanup.h shouldn't be
used.

> I will try to incorporate it if I do another revision. Although I do
> not think it improves things in this case as the function does not
> have multiple return statements.
>
> > > + if (!readbuf)
> > > + return -ENOMEM;
> > > +
> > > + ret = hid_hw_raw_request(hdev, report_id, readbuf,
> > > + FEATURE_KBD_REPORT_SIZE, HID_FEATURE_REPORT,
> > > + HID_REQ_GET_REPORT);
> > > + 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.
> > > + */
> > > + }
> > >
> > > + kfree(readbuf);
> > > return ret;
> > > }
> > >
> >
>

--
i.