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Date:   Mon, 06 Nov 2023 03:57:39 +0000
To:     Su Hui <suhui@nfschina.com>
From:   Rahul Rameshbabu <sergeantsagara@protonmail.com>
Cc:     ping.cheng@wacom.com, jason.gerecke@wacom.com, jikos@kernel.org,
        benjamin.tissoires@redhat.com, linux-input@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] HID: wacom_sys: add error code check in wacom_feature_mapping
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On Fri, 20 Oct, 2023 17:02:38 +0800 "Su Hui" <suhui@nfschina.com> wrote:
> hid_report_raw_event() can return error code like '-ENOMEM' if
> failed, so check 'ret' to make sure all things work fine.

I can agree with adding logging for error cases personally.

>
> Signed-off-by: Su Hui <suhui@nfschina.com>
> ---
>  drivers/hid/wacom_sys.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c
> index 3f704b8072e8..1f898d4ee708 100644
> --- a/drivers/hid/wacom_sys.c
> +++ b/drivers/hid/wacom_sys.c
> @@ -320,6 +320,8 @@ static void wacom_feature_mapping(struct hid_device *=
hdev,
>  =09=09=09if (ret =3D=3D n && features->type =3D=3D HID_GENERIC) {
>  =09=09=09=09ret =3D hid_report_raw_event(hdev,
>  =09=09=09=09=09HID_FEATURE_REPORT, data, n, 0);
> +=09=09=09=09if (ret)
> +=09=09=09=09=09hid_warn(hdev, "failed to report feature\n");

I think we should report the returned error information as well.

  https://docs.kernel.org/core-api/printk-formats.html#error-pointers

Typically what I do is use ERR_PTR in tandem with the %pe modifier for
printing errors.

>  =09=09=09} else if (ret =3D=3D 2 && features->type !=3D HID_GENERIC) {
>  =09=09=09=09features->touch_max =3D data[1];
>  =09=09=09} else {
> @@ -381,6 +383,8 @@ static void wacom_feature_mapping(struct hid_device *=
hdev,
>  =09=09if (ret =3D=3D n) {
>  =09=09=09ret =3D hid_report_raw_event(hdev, HID_FEATURE_REPORT,
>  =09=09=09=09=09=09   data, n, 0);
> +=09=09=09if (ret)
> +=09=09=09=09hid_warn(hdev, "failed to report feature\n");
>  =09=09} else {
>  =09=09=09hid_warn(hdev, "%s: could not retrieve sensor offsets\n",
>  =09=09=09=09 __func__);

--
Thanks for the patch,

Rahul Rameshbabu