Date:   Fri, 10 Feb 2023 23:20:43 +1100
From:   Orlando Chamberlain <orlandoch.dev@gmail.com>
To:     Aditya Garg <gargaditya08@live.com>
Cc:     Thomas =?UTF-8?B?V2Vpw59zY2h1aA==?= <thomas@t-8ch.de>,
        Jiri Kosina <jikos@kernel.org>,
        "jkosina@suse.cz" <jkosina@suse.cz>,
        "benjamin.tissoires@redhat.com" <benjamin.tissoires@redhat.com>,
        Andy Shevchenko <andy@infradead.org>,
        "andy.shevchenko@gmail.com" <andy.shevchenko@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
        "ronald@innovation.ch" <ronald@innovation.ch>,
        "kekrby@gmail.com" <kekrby@gmail.com>
Subject: Re: [PATCH 1/3] HID: apple-ibridge: Add Apple iBridge HID driver
 for T1 chip.
Message-ID: <20230210232043.18483401@redecorated-mbp>
In-Reply-To: <B9E319F8-6047-40E5-BD9F-D90D6504AA9E@live.com>
References: <E5D8BEBA-3C5B-460F-BD2C-39470A793CC3@live.com>
        <40274C3D-4F4F-479C-944C-EEBDC78F959C@live.com>
        <20230210045624.cjxroikmmvm3liij@t-8ch.de>
        <B9E319F8-6047-40E5-BD9F-D90D6504AA9E@live.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Fri, 10 Feb 2023 12:05:13 +0000
Aditya Garg <gargaditya08@live.com> wrote:

> > On 10-Feb-2023, at 10:26 AM, Thomas Wei=C3=9Fschuh <thomas@t-8ch.de>
> > wrote:
> >=20
> > Hi,
> >=20
> > some comments inline.
> >=20
> > On Fri, Feb 10, 2023 at 03:43:24AM +0000, Aditya Garg wrote:
> >  =20
> >> +
> >> +static struct {
> >> + unsigned int usage;
> >> + struct hid_device_id *dev_id;
> >> +} appleib_usage_map[] =3D {
> >> + /* Default iBridge configuration, key inputs and mode settings */
> >> + { 0x00010006, &appleib_sub_hid_ids[0] },
> >> + /* OS X iBridge configuration, digitizer inputs */
> >> + { 0x000D0005, &appleib_sub_hid_ids[0] },
> >> + /* All iBridge configurations, display/DFR settings */
> >> + { 0xFF120001, &appleib_sub_hid_ids[0] },
> >> + /* All iBridge configurations, ALS */
> >> + { 0x00200041, &appleib_sub_hid_ids[1] },
> >> +}; =20
> >=20
> > const
> >  =20
>=20
> Constantifying this results in compiler giving warnings
>=20
> drivers/hid/apple-ibridge.c:78:23: warning: initialization discards
> 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
> 78 |         { 0x00200041, &appleib_sub_hid_ids[1] }, |
>         ^ drivers/hid/apple-ibridge.c: In function
> 'appleib_add_sub_dev': drivers/hid/apple-ibridge.c:363:29: warning:
> assignment discards 'const' qualifier from pointer target type
> [-Wdiscarded-qualifiers] 363 |         sub_hdev->ll_driver =3D
> &appleib_ll_driver; |                             ^
> drivers/hid/apple-ibridge.c: In function 'appleib_hid_probe':
> drivers/hid/apple-ibridge.c:436:12: error: expected '(' before
> 'hid_is_usb' 436 |         if hid_is_usb(hdev) |            ^~~~~~~~~~
>       |            (
> In file included from drivers/hid/apple-ibridge.c:48:
> drivers/hid/apple-ibridge.c: In function 'appleib_probe':
> drivers/hid/apple-ibridge.c:544:35: warning: passing argument 1 of
> '__hid_register_driver' discards 'const' qualifier from pointer
> target type [-Wdiscarded-qualifiers] 544 |         ret =3D
> hid_register_driver(&appleib_hid_driver); |
>         ^~~~~~~~~~~~~~~~~~~ ./include/linux/hid.h:898:31: note: in
> definition of macro 'hid_register_driver' 898 |
> __hid_register_driver(driver, THIS_MODULE, KBUILD_MODNAME) |
>                      ^~~~~~ ./include/linux/hid.h:893:47: note:
> expected 'struct hid_driver *' but argument is of type 'const struct
> hid_driver *' 893 | extern int __must_check
> __hid_register_driver(struct hid_driver *, |
>                      ^~~~~~~~~~~~~~~~~~~ drivers/hid/apple-ibridge.c:
> In function 'appleib_remove': drivers/hid/apple-ibridge.c:558:31:
> warning: passing argument 1 of 'hid_unregister_driver' discards
> 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
> 558 |         hid_unregister_driver(&appleib_hid_driver); |
>                     ^~~~~~~~~~~~~~~~~~~ ./include/linux/hid.h:900:35:
> note: expected 'struct hid_driver *' but argument is of type 'const
> struct hid_driver *' 900 | extern void hid_unregister_driver(struct
> hid_driver *); |
> ^~~~~~~~~~~~~~~~~~~ make[6]: *** [scripts/Makefile.build:250:
> drivers/hid/apple-ibridge.o] Error 1 make[5]: ***
> [scripts/Makefile.build:500: drivers/hid] Error 2 make[5]: ***
> Waiting for unfinished jobs=E2=80=A6.
>=20
> Some warnings are also due to a typo in if and constantifying `static
> struct hid_driver`, although they probably can be fixed.
>=20
> In short, Thomas, do you really want me to constantify the structure
> I am talking about in this email, as well `static struct hid_driver`?
>=20

Were the changes needed for these structs to be const in the
linux-input tree for 6.3? If so then if you're applying the patches
onto linus' tree that might be why there are errors about consts.