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SubjectRe: [PATCH] HID: nintendo: check analog user calibration for plausibility
On Wed, Sep 14, 2022 at 9:51 AM Johnothan King
<johnothanking@protonmail.com> wrote:
>
> Arne Wendt writes:
> Cheap clone controllers may (falsely) report as having a user
> calibration for the analog sticks in place, but return
> wrong/impossible values for the actual calibration data.
> In the present case at mine, the controller reports having a
> user calibration in place and successfully executes the read
> commands. The reported user calibration however is
> min = center = max = 0.
>
> This pull request addresses problems of this kind by checking the
> provided user calibration-data for plausibility (min < center < max)
> and falling back to the default values if implausible.
>
> I'll note that I was experiencing a crash because of this bug when using
> the GuliKit KingKong 2 controller. The crash manifests as a divide by
> zero error in the kernel logs:
> kernel: divide error: 0000 [#1] PREEMPT SMP NOPTI
>
> Link: https://github.com/nicman23/dkms-hid-nintendo/pull/25
> Link: https://github.com/DanielOgorchock/linux/issues/36
> Co-authored-by: Arne Wendt <arne.wendt@tuhh.de>
> Signed-off-by: Johnothan King <johnothanking@protonmail.com>
> ---
> drivers/hid/hid-nintendo.c | 24 ++++++++++++++++++++++--
> 1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hid/hid-nintendo.c b/drivers/hid/hid-nintendo.c
> index 6028af3c3aae..7f287f6a75f5 100644
> --- a/drivers/hid/hid-nintendo.c
> +++ b/drivers/hid/hid-nintendo.c
> @@ -793,7 +793,17 @@ static int joycon_request_calibration(struct joycon_ctlr *ctlr)
> &ctlr->left_stick_cal_x,
> &ctlr->left_stick_cal_y,
> true);
> - if (ret) {
> +
> + /*
> + * Check whether read succeeded and perform plausibility check
> + * for retrieved values.
> + */
> + if (ret ||
> + ctlr->left_stick_cal_x.min >= ctlr->left_stick_cal_x.center ||
> + ctlr->left_stick_cal_x.center >= ctlr->left_stick_cal_x.max ||
> + ctlr->left_stick_cal_y.min >= ctlr->left_stick_cal_y.center ||
> + ctlr->left_stick_cal_y.center >= ctlr->left_stick_cal_y.max
> + ) {
> hid_warn(ctlr->hdev,
> "Failed to read left stick cal, using dflts; e=%d\n",
> ret);
> @@ -812,7 +822,17 @@ static int joycon_request_calibration(struct joycon_ctlr *ctlr)
> &ctlr->right_stick_cal_x,
> &ctlr->right_stick_cal_y,
> false);
> - if (ret) {
> +
> + /*
> + * Check whether read succeeded and perform plausibility check
> + * for retrieved values.
> + */
> + if (ret ||
> + ctlr->right_stick_cal_x.min >= ctlr->right_stick_cal_x.center ||
> + ctlr->right_stick_cal_x.center >= ctlr->right_stick_cal_x.max ||
> + ctlr->right_stick_cal_y.min >= ctlr->right_stick_cal_y.center ||
> + ctlr->right_stick_cal_y.center >= ctlr->right_stick_cal_y.max

Wouldn't it make sense to have a function that takes a single struct
joycon_stick_cal pointer and does the check?
This would make things more readable IMO.

Cheers,
Benjamin

> + ) {
> hid_warn(ctlr->hdev,
> "Failed to read right stick cal, using dflts; e=%d\n",
> ret);
> --
> 2.37.3
>
>

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