drm/privacy-screen: Fix sphinx warning

Fix the following warning from "make htmldocs":

drivers/gpu/drm/drm_privacy_screen.c:392:
warning: Function parameter or member 'data' not described in
'drm_privacy_screen_register'

Fixes: 30598d925d46 ("drm/privacy_screen: Add drvdata in drm_privacy_screen")
Cc: Rajat Jain <rajatja@google.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20220207113307.346281-1-hdegoede@redhat.com

drm/privacy_screen: Add drvdata in drm_privacy_screen

Allow a privacy screen provider to stash its private data pointer in the
drm_privacy_screen, and update the drm_privacy_screen_register() call to
accept that. Also introduce a *_get_drvdata() so that it can retrieved
back when needed.

This also touches the IBM Thinkpad platform driver, the only user of
privacy screen today, to pass NULL for now to the updated API.

Signed-off-by: Rajat Jain <rajatja@google.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220107190208.95479-1-rajatja@google.com

drm/privacy-screen: Fix sphinx warning

Fix the following warning from "make htmldocs":

drivers/gpu/drm/drm_privacy_screen.c:270:
WARNING: Inline emphasis start-string without end-string.

Fixes: 8a12b170558a ("drm/privacy-screen: Add notifier support (v2)")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Link: https://lore.kernel.org/r/20220207130407.389585-1-hdegoede@redhat.com
Link: https://patchwork.freedesktop.org/patch/msgid/20220207130407.389585-1-hdegoede@redhat.com

drm/privacy-screen: Add notifier support (v2)

Add support for privacy-screen consumers to register a notifier to
be notified of external (e.g. done by the hw itself on a hotkey press)
state changes.

Changes in v2:
- Drop WARN_ON(mutex_is_locked(&priv->lock)) check in
drm_privacy_screen_call_notifier_chain() it may be locked by
another thread, which would lead to a false-positive triggering
of the check

Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005202322.700909-5-hdegoede@redhat.com

drm: Add privacy-screen class (v4)

On some new laptops the LCD panel has a builtin electronic privacy-screen.
We want to export this functionality as a property on the drm connector
object. But often this functionality is not exposed on the GPU but on some
other (ACPI) device.

This commit adds a privacy-screen class allowing the driver for these
other devices to register themselves as a privacy-screen provider; and
allowing the drm/kms code to get a privacy-screen provider associated
with a specific GPU/connector combo.

Changes in v2:
- Make CONFIG_DRM_PRIVACY_SCREEN a bool which controls if the drm_privacy
code gets built as part of the main drm module rather then making it
a tristate which builds its own module.
- Add a #if IS_ENABLED(CONFIG_DRM_PRIVACY_SCREEN) check to
drm_privacy_screen_consumer.h and define stubs when the check fails.
Together these 2 changes fix several dependency issues.
- Remove module related code now that this is part of the main drm.ko
- Use drm_class as class for the privacy-screen devices instead of
adding a separate class for this

Changes in v3:
- Make the static inline drm_privacy_screen_get_state() stub set sw_state
and hw_state to PRIVACY_SCREEN_DISABLED to squelch an uninitialized
variable warning when CONFIG_DRM_PRIVICAY_SCREEN is not set

Changes in v4:
- Make drm_privacy_screen_set_sw_state() skip calling out to the hw if
hw_state == new_sw_state

Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005202322.700909-3-hdegoede@redhat.com