linux-kernel - Re: [PATCH 5/6] platform/x86: ideapad-laptop: Expose camera

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Date:   Fri, 28 Oct 2022 19:23:14 +0300
From:   Eray Orçunus <erayorcunus@...il.com>
To:     pobrn@...tonmail.com
Cc:     benjamin.tissoires@...hat.com, dmitry.torokhov@...il.com,
        erayorcunus@...il.com, hdegoede@...hat.com, ike.pan@...onical.com,
        jikos@...nel.org, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, mgross@...ux.intel.com,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH 5/6] platform/x86: ideapad-laptop: Expose camera_power only if supported

On Thu, 27 Oct 2022 19:43:29 +0000 Barnab=C3=A1s P=C5=91cze <pobrn@...tonmail.com> wrote:

> Hi
> 
> 
> 2022. okt=C3=B3ber 26., szerda 21:01 keltez=C3=A9ssel, Eray Or=C3=A7unus =
> =C3=ADrta:
> 
> > IdeaPads dropped support for VPCCMD_W_CAMERA somewhere between 2014-2016,
> > none of the IdeaPads produced after that I tested supports it. Fortunatel=
> y
> > I found a way to check it; if the DSDT has camera device(s) defined, it
> > shouldn't have working VPCCMD_W_CAMERA, thus camera_power shouldn't be
> > exposed to sysfs. To accomplish this, walk the ACPI namespace in
> > ideapad_check_features and check the devices starting with "CAM".
> > Tested on 520-15IKB and Legion Y520, which successfully didn't expose
> > the camera_power attribute.
> >=20
> > Link: https://www.spinics.net/lists/platform-driver-x86/msg26147.html
> > Signed-off-by: Eray Or=C3=A7unus <erayorcunus@...il.com>
> > ---
> >  drivers/platform/x86/ideapad-laptop.c | 53 ++++++++++++++++++++++++++-
> >  1 file changed, 52 insertions(+), 1 deletion(-)
> >=20
> > diff --git a/drivers/platform/x86/ideapad-laptop.c b/drivers/platform/x86=
> /ideapad-laptop.c
> > index f3d4f2beda07..65eea2e65bbe 100644
> > --- a/drivers/platform/x86/ideapad-laptop.c
> > +++ b/drivers/platform/x86/ideapad-laptop.c
> > @@ -149,6 +149,7 @@ struct ideapad_private {
> >  =09=09bool fn_lock              : 1;
> >  =09=09bool hw_rfkill_switch     : 1;
> >  =09=09bool kbd_bl               : 1;
> > +=09=09bool cam_ctrl_via_ec      : 1;
> >  =09=09bool touchpad_ctrl_via_ec : 1;
> >  =09=09bool usb_charging         : 1;
> >  =09} features;
> > @@ -163,6 +164,26 @@ static bool no_bt_rfkill;
> >  module_param(no_bt_rfkill, bool, 0444);
> >  MODULE_PARM_DESC(no_bt_rfkill, "No rfkill for bluetooth.");
> >=20
> > +static char *cam_device_prefix =3D "CAM";
> > +
> > +static acpi_status acpi_find_device_callback(acpi_handle handle, u32 lev=
> el,
> > +=09=09=09=09=09     void *context, void **return_value)
> > +{
> > +=09char buffer[8];
> > +=09struct acpi_buffer ret_buf;
> > +
> > +=09ret_buf.length =3D sizeof(buffer);
> > +=09ret_buf.pointer =3D buffer;
> > +
> > +=09if (ACPI_SUCCESS(acpi_get_name(handle, ACPI_SINGLE_NAME, &ret_buf)))
> > +=09=09if (strncmp(ret_buf.pointer, context, strlen(context)) =3D=3D 0) {
> 
> Please use `strstarts()` here. Is there any reason why you decided not to
> simply "inline" the "CAM" string here (or even in the function call)?

I may use this function to find other devices in future
(thus the name `acpi_find_device_callback`) and I've found a code in the kernel
which use static global initialization like that, so I decided to go for it in here.
But now I will create the "CAM" string inline, and I will also use `strstarts()`
(I didn't know such a function existed), thank you.

> 
> 
> > +=09=09=09*return_value =3D handle;
> > +=09=09=09return AE_CTRL_TERMINATE;
> > +=09=09}
> > +
> > +=09return AE_OK;
> > +}
> > +
> >  /*
> >   * ACPI Helpers
> >   */
> > @@ -675,7 +696,7 @@ static umode_t ideapad_is_visible(struct kobject *kob=
> j,
> >  =09bool supported =3D true;
> >=20
> >  =09if (attr =3D=3D &dev_attr_camera_power.attr)
> > -=09=09supported =3D test_bit(CFG_CAP_CAM_BIT, &priv->cfg);
> > +=09=09supported =3D priv->features.cam_ctrl_via_ec;
> >  =09else if (attr =3D=3D &dev_attr_conservation_mode.attr)
> >  =09=09supported =3D priv->features.conservation_mode;
> >  =09else if (attr =3D=3D &dev_attr_fan_mode.attr)
> > @@ -1523,10 +1544,40 @@ static const struct dmi_system_id hw_rfkill_list[=
> ] =3D {
> >  static void ideapad_check_features(struct ideapad_private *priv)
> >  {
> >  =09acpi_handle handle =3D priv->adev->handle;
> > +=09acpi_handle pci_handle;
> > +=09acpi_handle temp_handle =3D NULL;
> >  =09unsigned long val;
> > +=09acpi_status status;
> 
> It is a small thing, but I believe it is best to define these variables
> in the block of that `if` since they are not used outside of it.

Ok, will do in next revision, thank you.

-eray