netdev - Re: [PATCH 2/8] HID: usbhid: Make hid_is

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Date:   Thu, 22 Dec 2022 22:12:00 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        David Rheinsberg <david.rheinsberg@...il.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2/8] HID: usbhid: Make hid_is_usb() non-inline

On Thu, Dec 22, 2022 at 6:16 AM Thomas Weißschuh <linux@...ssschuh.net> wrote:
>
> By making hid_is_usb() a non-inline function the lowlevel usbhid driver
> does not have to be exported anymore.
>
> Also mark the argument as const as it is not modified.
>
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
>  drivers/hid/usbhid/hid-core.c | 6 ++++++
>  include/linux/hid.h           | 5 +----
>  2 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
> index be4c731aaa65..54b0280d0073 100644
> --- a/drivers/hid/usbhid/hid-core.c
> +++ b/drivers/hid/usbhid/hid-core.c
> @@ -1334,6 +1334,12 @@ struct hid_ll_driver usb_hid_driver = {
>  };
>  EXPORT_SYMBOL_GPL(usb_hid_driver);
>
> +bool hid_is_usb(const struct hid_device *hdev)
> +{
> +       return hdev->ll_driver == &usb_hid_driver;
> +}
> +EXPORT_SYMBOL_GPL(hid_is_usb);
> +
>  static int usbhid_probe(struct usb_interface *intf, const struct usb_device_id *id)
>  {
>         struct usb_host_interface *interface = intf->cur_altsetting;
> diff --git a/include/linux/hid.h b/include/linux/hid.h
> index 8677ae38599e..e8400aa78522 100644
> --- a/include/linux/hid.h
> +++ b/include/linux/hid.h
> @@ -864,10 +864,7 @@ static inline bool hid_is_using_ll_driver(struct hid_device *hdev,
>         return hdev->ll_driver == driver;
>  }
>
> -static inline bool hid_is_usb(struct hid_device *hdev)
> -{
> -       return hid_is_using_ll_driver(hdev, &usb_hid_driver);
> -}
> +extern bool hid_is_usb(const struct hid_device *hdev);

The problem here is that CONFIG_USB_HID can be set to either m or n.
In the n case, you'll end up with an undefined symbol, in the m case,
it won't link too if CONFIG_HID is set to Y (and it'll be quite a mess
to call it if the module is not loaded yet).

Cheers,
Benjamin


>
>
>  #define        PM_HINT_FULLON  1<<5
>  #define PM_HINT_NORMAL 1<<1
>
> --
> 2.39.0
>