Re: [PATCH resend 2/4] backlight: Add backlight device (un)registration notification

[Jingoo Han <jg1.han@samsung.com>]

On Thursday, May 22, 2014 6:02 PM, Lee Jones wrote:
> On Thursday, May 22, 2014 5:45 PM, Hans de Goede wrote:
> > On Thursday, May 22, 2014 8:31 AM, Rafael J. Wysocki wrote:
> > > On Wednesday, May 21, 2014 10:40 PM, Hans de Goede wrote:
> > >> Some firmware drivers, ie acpi-video want to get themselves out of the
> > >> way (in some cases) when their also is a raw backlight device available.
> > >>
> > >> Due to module loading ordering being unknown, acpi-video cannot be certain
> > >> that the backlight_device_registered(BACKLIGHT_RAW) it does for this is
> > >> the final verdict wrt there being a BACKLIGHT_RAW device.
> > >>
> > >> By adding notification acpi-video can listen for backlight devices showing
> > >> up after it has loaded, and unregister its backlight device if desired.
> > >>
> > >> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> > >
> > > Backlight maintainer's ACK is requisite here.
> >
> > Agreed, which is why I send this set to all 3 the backlight maintainers
> > directly on both postings.
> >
> > What may be helpful for them is to hear from you if you're ok with the
> > acpi-video bits which are actually going to use this, since those will
> > be the only user of the new backlight api (for now).
> 
> I'm happy to apply any Backlight patches which have either Bryan or
> Jingoo's Ack, as they are the reviewers for the BL subsystem.

Acked-by: Jingoo Han <jg1.han@samsung.com>

Lee Jones,
Would you merge this patch into your backlight git tree?
Thank you.

Best regards,
Jingoo Han

> 
> > >> ---
> > >>  drivers/video/backlight/backlight.c | 40 +++++++++++++++++++++++++++++++++++++
> > >>  include/linux/backlight.h           |  7 +++++++
> > >>  2 files changed, 47 insertions(+)
> > >>
> > >> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> > >> index bd2172c..4280890 100644
> > >> --- a/drivers/video/backlight/backlight.c
> > >> +++ b/drivers/video/backlight/backlight.c
> > >> @@ -23,6 +23,7 @@
> > >>
> > >>  static struct list_head backlight_dev_list;
> > >>  static struct mutex backlight_dev_list_mutex;
> > >> +static struct blocking_notifier_head backlight_notifier;
> > >>
> > >>  static const char *const backlight_types[] = {
> > >>  	[BACKLIGHT_RAW] = "raw",
> > >> @@ -370,6 +371,9 @@ struct backlight_device *backlight_device_register(const char *name,
> > >>  	list_add(&new_bd->entry, &backlight_dev_list);
> > >>  	mutex_unlock(&backlight_dev_list_mutex);
> > >>
> > >> +	blocking_notifier_call_chain(&backlight_notifier,
> > >> +				     BACKLIGHT_REGISTERED, new_bd);
> > >> +
> > >>  	return new_bd;
> > >>  }
> > >>  EXPORT_SYMBOL(backlight_device_register);
> > >> @@ -413,6 +417,10 @@ void backlight_device_unregister(struct backlight_device *bd)
> > >>  		pmac_backlight = NULL;
> > >>  	mutex_unlock(&pmac_backlight_mutex);
> > >>  #endif
> > >> +
> > >> +	blocking_notifier_call_chain(&backlight_notifier,
> > >> +				     BACKLIGHT_UNREGISTERED, bd);
> > >> +
> > >>  	mutex_lock(&bd->ops_lock);
> > >>  	bd->ops = NULL;
> > >>  	mutex_unlock(&bd->ops_lock);
> > >> @@ -438,6 +446,36 @@ static int devm_backlight_device_match(struct device *dev, void *res,
> > >>  }
> > >>
> > >>  /**
> > >> + * backlight_register_notifier - get notified of backlight (un)registration
> > >> + * @nb: notifier block with the notifier to call on backlight (un)registration
> > >> + *
> > >> + * @return 0 on success, otherwise a negative error code
> > >> + *
> > >> + * Register a notifier to get notified when backlight devices get registered
> > >> + * or unregistered.
> > >> + */
> > >> +int backlight_register_notifier(struct notifier_block *nb)
> > >> +{
> > >> +	return blocking_notifier_chain_register(&backlight_notifier, nb);
> > >> +}
> > >> +EXPORT_SYMBOL(backlight_register_notifier);
> > >> +
> > >> +/**
> > >> + * backlight_unregister_notifier - unregister a backlight notifier
> > >> + * @nb: notifier block to unregister
> > >> + *
> > >> + * @return 0 on success, otherwise a negative error code
> > >> + *
> > >> + * Register a notifier to get notified when backlight devices get registered
> > >> + * or unregistered.
> > >> + */
> > >> +int backlight_unregister_notifier(struct notifier_block *nb)
> > >> +{
> > >> +	return blocking_notifier_chain_unregister(&backlight_notifier, nb);
> > >> +}
> > >> +EXPORT_SYMBOL(backlight_unregister_notifier);
> > >> +
> > >> +/**
> > >>   * devm_backlight_device_register - resource managed backlight_device_register()
> > >>   * @dev: the device to register
> > >>   * @name: the name of the device
> > >> @@ -544,6 +582,8 @@ static int __init backlight_class_init(void)
> > >>  	backlight_class->pm = &backlight_class_dev_pm_ops;
> > >>  	INIT_LIST_HEAD(&backlight_dev_list);
> > >>  	mutex_init(&backlight_dev_list_mutex);
> > >> +	BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);
> > >> +
> > >>  	return 0;
> > >>  }
> > >>
> > >> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> > >> index 7264742..adb14a8 100644
> > >> --- a/include/linux/backlight.h
> > >> +++ b/include/linux/backlight.h
> > >> @@ -40,6 +40,11 @@ enum backlight_type {
> > >>  	BACKLIGHT_TYPE_MAX,
> > >>  };
> > >>
> > >> +enum backlight_notification {
> > >> +	BACKLIGHT_REGISTERED,
> > >> +	BACKLIGHT_UNREGISTERED,
> > >> +};
> > >> +
> > >>  struct backlight_device;
> > >>  struct fb_info;
> > >>
> > >> @@ -133,6 +138,8 @@ extern void devm_backlight_device_unregister(struct device *dev,
> > >>  extern void backlight_force_update(struct backlight_device *bd,
> > >>  				   enum backlight_update_reason reason);
> > >>  extern bool backlight_device_registered(enum backlight_type type);
> > >> +extern int backlight_register_notifier(struct notifier_block *nb);
> > >> +extern int backlight_unregister_notifier(struct notifier_block *nb);
> > >>
> > >>  #define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)