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

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Message-ID: <4d42a44d-e0f3-4d01-8564-267d0f3f061a@t-8ch.de>
Date:   Thu, 22 Dec 2022 16:37:21 -0500 (EST)
From:   Thomas Weißschuh  <thomas@...ch.de>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Thomas Weißschuh <linux@...ssschuh.net>,
        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


Dec 22, 2022 16:13:06 Benjamin Tissoires <benjamin.tissoires@...hat.com>:

> 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).

Shouldn't we already have the same problem with
the symbol usb_hid_driver itself that is defined
right next to the new hid_is_usb()?

Thomas

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