[PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Hans de Goede]

On some systems acpi-video backlight is broken in the sense that it cannot
control the brightness of the backlight, but it must still be called on
resume to power-up the backlight after resume.

This commit allows these systems to work by going through all the usual
backlight control moves, while not registering a sysfs backlight
interface.

This commit also adds a quirk enabling this parameter on Toshiba Portege
R830 systems which are known to be affected by this.

I wish there was a better way to deal with this, but we've been unable to
find one.

Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=21012
Buglink: https://bugs.freedesktop.org/show_bug.cgi?id=82634
Reported-and-tested-by: Sylvain Pasche <sylvain.pasche@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
-Simplify check in acpi_video_switch_brightness()
-If backlight registration fails set device->backlight to NULL, rather
 then leaving the PTR_ERR in there and trying to deref this later
 (this fixes a pre-existing bug)
---
 drivers/acpi/video.c | 43 +++++++++++++++++++++++++++++++++++++++----
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 518f0e1..3bc4c68 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -92,6 +92,9 @@ static int use_native_backlight_param = NATIVE_BACKLIGHT_NOT_SET;
 module_param_named(use_native_backlight, use_native_backlight_param, int, 0444);
 static int use_native_backlight_dmi = NATIVE_BACKLIGHT_NOT_SET;
 
+static int disable_backlight_sysfs_if = -1;
+module_param(disable_backlight_sysfs_if, int, 0444);
+
 static int register_count;
 static struct mutex video_list_lock;
 static struct list_head video_bus_head;
@@ -431,6 +434,14 @@ static int __init video_enable_native_backlight(const struct dmi_system_id *d)
 	return 0;
 }
 
+static int __init video_disable_backlight_sysfs_if(
+	const struct dmi_system_id *d)
+{
+	if (disable_backlight_sysfs_if == -1)
+		disable_backlight_sysfs_if = 1;
+	return 0;
+}
+
 static struct dmi_system_id video_dmi_table[] __initdata = {
 	/*
 	 * Broken _BQC workaround http://bugzilla.kernel.org/show_bug.cgi?id=13121
@@ -592,6 +603,23 @@ static struct dmi_system_id video_dmi_table[] __initdata = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
 		},
 	},
+
+	/*
+	 * Some machines have a broken acpi-video interface for brightness
+	 * control, but still need an acpi_video_device_lcd_set_level() call
+	 * on resume to turn the backlight power on.  We Enable backlight
+	 * control on these systems, but do not register a backlight sysfs
+	 * as brightness control does not work.
+	 */
+	{
+	 /* https://bugs.freedesktop.org/show_bug.cgi?id=82634 */
+	 .callback = video_disable_backlight_sysfs_if,
+	 .ident = "Toshiba Portege R830",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "PORTEGE R830"),
+		},
+	},
 	{}
 };
 
@@ -1391,7 +1419,7 @@ acpi_video_switch_brightness(struct work_struct *work)
 	int result = -EINVAL;
 
 	/* no warning message if acpi_backlight=vendor or a quirk is used */
-	if (!acpi_video_verify_backlight_support())
+	if (!device->backlight)
 		return;
 
 	if (!device->brightness)
@@ -1666,8 +1694,9 @@ static int acpi_video_resume(struct notifier_block *nb,
 
 	for (i = 0; i < video->attached_count; i++) {
 		video_device = video->attached_array[i].bind_info;
-		if (video_device && video_device->backlight)
-			acpi_video_set_brightness(video_device->backlight);
+		if (video_device && video_device->brightness)
+			acpi_video_device_lcd_set_level(video_device,
+					video_device->brightness->curr);
 	}
 
 	return NOTIFY_OK;
@@ -1716,6 +1745,10 @@ static void acpi_video_dev_register_backlight(struct acpi_video_device *device)
 	result = acpi_video_init_brightness(device);
 	if (result)
 		return;
+
+	if (disable_backlight_sysfs_if > 0)
+		return;
+
 	name = kasprintf(GFP_KERNEL, "acpi_video%d", count);
 	if (!name)
 		return;
@@ -1738,8 +1771,10 @@ static void acpi_video_dev_register_backlight(struct acpi_video_device *device)
 						      &acpi_backlight_ops,
 						      &props);
 	kfree(name);
-	if (IS_ERR(device->backlight))
+	if (IS_ERR(device->backlight)) {
+		device->backlight = NULL;
 		return;
+	}
 
 	/*
 	 * Save current brightness level in case we have to restore it
-- 
2.4.2

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Re: [PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Aaron Lu]

On Tue, Jun 09, 2015 at 10:32:25AM +0200, Hans de Goede wrote:
> On some systems acpi-video backlight is broken in the sense that it cannot
> control the brightness of the backlight, but it must still be called on
> resume to power-up the backlight after resume.

All the video module does on resume is a backlight set operation, it
can't control backlight but can turn on the screen on resume? Hmm...

I'll ask Sylvain to attach acpidump, let's see if there is anything
special there.

Regards,
Aaron

> 
> This commit allows these systems to work by going through all the usual
> backlight control moves, while not registering a sysfs backlight
> interface.
> 
> This commit also adds a quirk enabling this parameter on Toshiba Portege
> R830 systems which are known to be affected by this.
> 
> I wish there was a better way to deal with this, but we've been unable to
> find one.
> 
> Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=21012
> Buglink: https://bugs.freedesktop.org/show_bug.cgi?id=82634
> Reported-and-tested-by: Sylvain Pasche <sylvain.pasche@gmail.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v2:
> -Simplify check in acpi_video_switch_brightness()
> -If backlight registration fails set device->backlight to NULL, rather
>  then leaving the PTR_ERR in there and trying to deref this later
>  (this fixes a pre-existing bug)
> ---
>  drivers/acpi/video.c | 43 +++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 39 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> index 518f0e1..3bc4c68 100644
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -92,6 +92,9 @@ static int use_native_backlight_param = NATIVE_BACKLIGHT_NOT_SET;
>  module_param_named(use_native_backlight, use_native_backlight_param, int, 0444);
>  static int use_native_backlight_dmi = NATIVE_BACKLIGHT_NOT_SET;
>  
> +static int disable_backlight_sysfs_if = -1;
> +module_param(disable_backlight_sysfs_if, int, 0444);
> +
>  static int register_count;
>  static struct mutex video_list_lock;
>  static struct list_head video_bus_head;
> @@ -431,6 +434,14 @@ static int __init video_enable_native_backlight(const struct dmi_system_id *d)
>  	return 0;
>  }
>  
> +static int __init video_disable_backlight_sysfs_if(
> +	const struct dmi_system_id *d)
> +{
> +	if (disable_backlight_sysfs_if == -1)
> +		disable_backlight_sysfs_if = 1;
> +	return 0;
> +}
> +
>  static struct dmi_system_id video_dmi_table[] __initdata = {
>  	/*
>  	 * Broken _BQC workaround http://bugzilla.kernel.org/show_bug.cgi?id=13121
> @@ -592,6 +603,23 @@ static struct dmi_system_id video_dmi_table[] __initdata = {
>  		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
>  		},
>  	},
> +
> +	/*
> +	 * Some machines have a broken acpi-video interface for brightness
> +	 * control, but still need an acpi_video_device_lcd_set_level() call
> +	 * on resume to turn the backlight power on.  We Enable backlight
> +	 * control on these systems, but do not register a backlight sysfs
> +	 * as brightness control does not work.
> +	 */
> +	{
> +	 /* https://bugs.freedesktop.org/show_bug.cgi?id=82634 */
> +	 .callback = video_disable_backlight_sysfs_if,
> +	 .ident = "Toshiba Portege R830",
> +	 .matches = {
> +		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
> +		DMI_MATCH(DMI_PRODUCT_NAME, "PORTEGE R830"),
> +		},
> +	},
>  	{}
>  };
>  
> @@ -1391,7 +1419,7 @@ acpi_video_switch_brightness(struct work_struct *work)
>  	int result = -EINVAL;
>  
>  	/* no warning message if acpi_backlight=vendor or a quirk is used */
> -	if (!acpi_video_verify_backlight_support())
> +	if (!device->backlight)
>  		return;
>  
>  	if (!device->brightness)
> @@ -1666,8 +1694,9 @@ static int acpi_video_resume(struct notifier_block *nb,
>  
>  	for (i = 0; i < video->attached_count; i++) {
>  		video_device = video->attached_array[i].bind_info;
> -		if (video_device && video_device->backlight)
> -			acpi_video_set_brightness(video_device->backlight);
> +		if (video_device && video_device->brightness)
> +			acpi_video_device_lcd_set_level(video_device,
> +					video_device->brightness->curr);
>  	}
>  
>  	return NOTIFY_OK;
> @@ -1716,6 +1745,10 @@ static void acpi_video_dev_register_backlight(struct acpi_video_device *device)
>  	result = acpi_video_init_brightness(device);
>  	if (result)
>  		return;
> +
> +	if (disable_backlight_sysfs_if > 0)
> +		return;
> +
>  	name = kasprintf(GFP_KERNEL, "acpi_video%d", count);
>  	if (!name)
>  		return;
> @@ -1738,8 +1771,10 @@ static void acpi_video_dev_register_backlight(struct acpi_video_device *device)
>  						      &acpi_backlight_ops,
>  						      &props);
>  	kfree(name);
> -	if (IS_ERR(device->backlight))
> +	if (IS_ERR(device->backlight)) {
> +		device->backlight = NULL;
>  		return;
> +	}
>  
>  	/*
>  	 * Save current brightness level in case we have to restore it
> -- 
> 2.4.2
> 

Re: [PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Jani Nikula]

On Tue, 09 Jun 2015, Hans de Goede <hdegoede@redhat.com> wrote:
> On some systems acpi-video backlight is broken in the sense that it cannot
> control the brightness of the backlight, but it must still be called on
> resume to power-up the backlight after resume.
>
> This commit allows these systems to work by going through all the usual
> backlight control moves, while not registering a sysfs backlight
> interface.
>
> This commit also adds a quirk enabling this parameter on Toshiba Portege
> R830 systems which are known to be affected by this.
>
> I wish there was a better way to deal with this, but we've been unable to
> find one.
>
> Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=21012
> Buglink: https://bugs.freedesktop.org/show_bug.cgi?id=82634
> Reported-and-tested-by: Sylvain Pasche <sylvain.pasche@gmail.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v2:
> -Simplify check in acpi_video_switch_brightness()
> -If backlight registration fails set device->backlight to NULL, rather
>  then leaving the PTR_ERR in there and trying to deref this later
>  (this fixes a pre-existing bug)
> ---
>  drivers/acpi/video.c | 43 +++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> index 518f0e1..3bc4c68 100644
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -92,6 +92,9 @@ static int use_native_backlight_param = NATIVE_BACKLIGHT_NOT_SET;
>  module_param_named(use_native_backlight, use_native_backlight_param, int, 0444);
>  static int use_native_backlight_dmi = NATIVE_BACKLIGHT_NOT_SET;
>  
> +static int disable_backlight_sysfs_if = -1;
> +module_param(disable_backlight_sysfs_if, int, 0444);

Nitpick, I'd prefer positively named variables, like enable_foo to avoid
the double negative !disable_foo. enable_foo and !enable_foo read much
better. But up to Aaron and friends.

BR,
Jani.


> +
>  static int register_count;
>  static struct mutex video_list_lock;
>  static struct list_head video_bus_head;
> @@ -431,6 +434,14 @@ static int __init video_enable_native_backlight(const struct dmi_system_id *d)
>  	return 0;
>  }
>  
> +static int __init video_disable_backlight_sysfs_if(
> +	const struct dmi_system_id *d)
> +{
> +	if (disable_backlight_sysfs_if == -1)
> +		disable_backlight_sysfs_if = 1;
> +	return 0;
> +}
> +
>  static struct dmi_system_id video_dmi_table[] __initdata = {
>  	/*
>  	 * Broken _BQC workaround http://bugzilla.kernel.org/show_bug.cgi?id=13121
> @@ -592,6 +603,23 @@ static struct dmi_system_id video_dmi_table[] __initdata = {
>  		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
>  		},
>  	},
> +
> +	/*
> +	 * Some machines have a broken acpi-video interface for brightness
> +	 * control, but still need an acpi_video_device_lcd_set_level() call
> +	 * on resume to turn the backlight power on.  We Enable backlight
> +	 * control on these systems, but do not register a backlight sysfs
> +	 * as brightness control does not work.
> +	 */
> +	{
> +	 /* https://bugs.freedesktop.org/show_bug.cgi?id=82634 */
> +	 .callback = video_disable_backlight_sysfs_if,
> +	 .ident = "Toshiba Portege R830",
> +	 .matches = {
> +		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
> +		DMI_MATCH(DMI_PRODUCT_NAME, "PORTEGE R830"),
> +		},
> +	},
>  	{}
>  };
>  
> @@ -1391,7 +1419,7 @@ acpi_video_switch_brightness(struct work_struct *work)
>  	int result = -EINVAL;
>  
>  	/* no warning message if acpi_backlight=vendor or a quirk is used */
> -	if (!acpi_video_verify_backlight_support())
> +	if (!device->backlight)
>  		return;
>  
>  	if (!device->brightness)
> @@ -1666,8 +1694,9 @@ static int acpi_video_resume(struct notifier_block *nb,
>  
>  	for (i = 0; i < video->attached_count; i++) {
>  		video_device = video->attached_array[i].bind_info;
> -		if (video_device && video_device->backlight)
> -			acpi_video_set_brightness(video_device->backlight);
> +		if (video_device && video_device->brightness)
> +			acpi_video_device_lcd_set_level(video_device,
> +					video_device->brightness->curr);
>  	}
>  
>  	return NOTIFY_OK;
> @@ -1716,6 +1745,10 @@ static void acpi_video_dev_register_backlight(struct acpi_video_device *device)
>  	result = acpi_video_init_brightness(device);
>  	if (result)
>  		return;
> +
> +	if (disable_backlight_sysfs_if > 0)
> +		return;
> +
>  	name = kasprintf(GFP_KERNEL, "acpi_video%d", count);
>  	if (!name)
>  		return;
> @@ -1738,8 +1771,10 @@ static void acpi_video_dev_register_backlight(struct acpi_video_device *device)
>  						      &acpi_backlight_ops,
>  						      &props);
>  	kfree(name);
> -	if (IS_ERR(device->backlight))
> +	if (IS_ERR(device->backlight)) {
> +		device->backlight = NULL;
>  		return;
> +	}
>  
>  	/*
>  	 * Save current brightness level in case we have to restore it
> -- 
> 2.4.2
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Jani Nikula, Intel Open Source Technology Center
_______________________________________________
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Re: [PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Hans de Goede]

Hi,

On 06/09/2015 11:10 AM, Aaron Lu wrote:
> On Tue, Jun 09, 2015 at 10:32:25AM +0200, Hans de Goede wrote:
>> On some systems acpi-video backlight is broken in the sense that it cannot
>> control the brightness of the backlight, but it must still be called on
>> resume to power-up the backlight after resume.
>
> All the video module does on resume is a backlight set operation, it
> can't control backlight but can turn on the screen on resume? Hmm...
>
> I'll ask Sylvain to attach acpidump, let's see if there is anything
> special there.

Ok, lets see what comes out of that. Note in the mean time Sylvain has
attached his acpidump.

Regards,

Hans

Re: [PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Aaron Lu]

On Tue, Jun 09, 2015 at 11:54:45PM +0200, Hans de Goede wrote:
> Hi,
> 
> On 06/09/2015 11:10 AM, Aaron Lu wrote:
> >On Tue, Jun 09, 2015 at 10:32:25AM +0200, Hans de Goede wrote:
> >>On some systems acpi-video backlight is broken in the sense that it cannot
> >>control the brightness of the backlight, but it must still be called on
> >>resume to power-up the backlight after resume.
> >
> >All the video module does on resume is a backlight set operation, it
> >can't control backlight but can turn on the screen on resume? Hmm...
> >
> >I'll ask Sylvain to attach acpidump, let's see if there is anything
> >special there.
> 
> Ok, lets see what comes out of that. Note in the mean time Sylvain has
> attached his acpidump.

Thanks.
According to the discussion in the bugzilla place, it doesn't seem we
have any other way to handle this at the moment.

Acked-by: Aaron Lu <aaron.lu@intel.com>

Best wishes,
Aaron

Re: [PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Hans de Goede]

Hi,

On 11-06-15 03:43, Aaron Lu wrote:
> On Tue, Jun 09, 2015 at 11:54:45PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 06/09/2015 11:10 AM, Aaron Lu wrote:
>>> On Tue, Jun 09, 2015 at 10:32:25AM +0200, Hans de Goede wrote:
>>>> On some systems acpi-video backlight is broken in the sense that it cannot
>>>> control the brightness of the backlight, but it must still be called on
>>>> resume to power-up the backlight after resume.
>>>
>>> All the video module does on resume is a backlight set operation, it
>>> can't control backlight but can turn on the screen on resume? Hmm...
>>>
>>> I'll ask Sylvain to attach acpidump, let's see if there is anything
>>> special there.
>>
>> Ok, lets see what comes out of that. Note in the mean time Sylvain has
>> attached his acpidump.
>
> Thanks.
> According to the discussion in the bugzilla place, it doesn't seem we
> have any other way to handle this at the moment.
>
> Acked-by: Aaron Lu <aaron.lu@intel.com>

Thanks. So that only leaves Jani's remark:

 > Nitpick, I'd prefer positively named variables, like enable_foo to avoid
 > the double negative !disable_foo. enable_foo and !enable_foo read much
 > better. But up to Aaron and friends.

I personally believe that having the option named disable_backlight_sysfs_if
is better here since I believe that things which are always enabled except
on a few broken model laptops the option name should be disable_foo so
that people can clearly see in /proc/cmdline / dmesg that the user is passing
an option to disable something which is normally enabled.

As for the (!disabled) argument, the code in question here actually is:

if (disabled)
	return 0;

:)

Still if people want me to change the option to a default-on
enable_backlight_sysfs_if option I can do a v3...

Regards,

Hans

Re: [PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Jani Nikula]

On Thu, 11 Jun 2015, Hans de Goede <hdegoede@redhat.com> wrote:
> Hi,
>
> On 11-06-15 03:43, Aaron Lu wrote:
>> On Tue, Jun 09, 2015 at 11:54:45PM +0200, Hans de Goede wrote:
>>> Hi,
>>>
>>> On 06/09/2015 11:10 AM, Aaron Lu wrote:
>>>> On Tue, Jun 09, 2015 at 10:32:25AM +0200, Hans de Goede wrote:
>>>>> On some systems acpi-video backlight is broken in the sense that it cannot
>>>>> control the brightness of the backlight, but it must still be called on
>>>>> resume to power-up the backlight after resume.
>>>>
>>>> All the video module does on resume is a backlight set operation, it
>>>> can't control backlight but can turn on the screen on resume? Hmm...
>>>>
>>>> I'll ask Sylvain to attach acpidump, let's see if there is anything
>>>> special there.
>>>
>>> Ok, lets see what comes out of that. Note in the mean time Sylvain has
>>> attached his acpidump.
>>
>> Thanks.
>> According to the discussion in the bugzilla place, it doesn't seem we
>> have any other way to handle this at the moment.
>>
>> Acked-by: Aaron Lu <aaron.lu@intel.com>
>
> Thanks. So that only leaves Jani's remark:
>
>  > Nitpick, I'd prefer positively named variables, like enable_foo to avoid
>  > the double negative !disable_foo. enable_foo and !enable_foo read much
>  > better. But up to Aaron and friends.
>
> I personally believe that having the option named disable_backlight_sysfs_if
> is better here since I believe that things which are always enabled except
> on a few broken model laptops the option name should be disable_foo so
> that people can clearly see in /proc/cmdline / dmesg that the user is passing
> an option to disable something which is normally enabled.

Fair enough.

>
> As for the (!disabled) argument, the code in question here actually is:
>
> if (disabled)
> 	return 0;
>
> :)
>
> Still if people want me to change the option to a default-on
> enable_backlight_sysfs_if option I can do a v3...

I'm not insisting.

BR,
Jani.


>
> Regards,
>
> Hans
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Jani Nikula, Intel Open Source Technology Center

Re: [PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Hans de Goede]

Hi,

On 11-06-15 13:10, Jani Nikula wrote:
> On Thu, 11 Jun 2015, Hans de Goede <hdegoede@redhat.com> wrote:
>> Hi,
>>
>> On 11-06-15 03:43, Aaron Lu wrote:
>>> On Tue, Jun 09, 2015 at 11:54:45PM +0200, Hans de Goede wrote:
>>>> Hi,
>>>>
>>>> On 06/09/2015 11:10 AM, Aaron Lu wrote:
>>>>> On Tue, Jun 09, 2015 at 10:32:25AM +0200, Hans de Goede wrote:
>>>>>> On some systems acpi-video backlight is broken in the sense that it cannot
>>>>>> control the brightness of the backlight, but it must still be called on
>>>>>> resume to power-up the backlight after resume.
>>>>>
>>>>> All the video module does on resume is a backlight set operation, it
>>>>> can't control backlight but can turn on the screen on resume? Hmm...
>>>>>
>>>>> I'll ask Sylvain to attach acpidump, let's see if there is anything
>>>>> special there.
>>>>
>>>> Ok, lets see what comes out of that. Note in the mean time Sylvain has
>>>> attached his acpidump.
>>>
>>> Thanks.
>>> According to the discussion in the bugzilla place, it doesn't seem we
>>> have any other way to handle this at the moment.
>>>
>>> Acked-by: Aaron Lu <aaron.lu@intel.com>
>>
>> Thanks. So that only leaves Jani's remark:
>>
>>   > Nitpick, I'd prefer positively named variables, like enable_foo to avoid
>>   > the double negative !disable_foo. enable_foo and !enable_foo read much
>>   > better. But up to Aaron and friends.
>>
>> I personally believe that having the option named disable_backlight_sysfs_if
>> is better here since I believe that things which are always enabled except
>> on a few broken model laptops the option name should be disable_foo so
>> that people can clearly see in /proc/cmdline / dmesg that the user is passing
>> an option to disable something which is normally enabled.
>
> Fair enough.
>
>>
>> As for the (!disabled) argument, the code in question here actually is:
>>
>> if (disabled)
>> 	return 0;
>>
>> :)
>>
>> Still if people want me to change the option to a default-on
>> enable_backlight_sysfs_if option I can do a v3...
>
> I'm not insisting.

Great, thanks :)

So I'm going to assume this v2 patch is ready for merging then, if anyone
wants me to make any changes please let me know.

Regards,

Hans

Re: [PATCH v2] acpi-video: Add a parameter to not register the backlight sysfs interface

[Rafael J. Wysocki]

On Thursday, June 11, 2015 02:13:55 PM Hans de Goede wrote:
> Hi,
> 
> On 11-06-15 13:10, Jani Nikula wrote:
> > On Thu, 11 Jun 2015, Hans de Goede <hdegoede@redhat.com> wrote:
> >> Hi,
> >>
> >> On 11-06-15 03:43, Aaron Lu wrote:
> >>> On Tue, Jun 09, 2015 at 11:54:45PM +0200, Hans de Goede wrote:
> >>>> Hi,
> >>>>
> >>>> On 06/09/2015 11:10 AM, Aaron Lu wrote:
> >>>>> On Tue, Jun 09, 2015 at 10:32:25AM +0200, Hans de Goede wrote:
> >>>>>> On some systems acpi-video backlight is broken in the sense that it cannot
> >>>>>> control the brightness of the backlight, but it must still be called on
> >>>>>> resume to power-up the backlight after resume.
> >>>>>
> >>>>> All the video module does on resume is a backlight set operation, it
> >>>>> can't control backlight but can turn on the screen on resume? Hmm...
> >>>>>
> >>>>> I'll ask Sylvain to attach acpidump, let's see if there is anything
> >>>>> special there.
> >>>>
> >>>> Ok, lets see what comes out of that. Note in the mean time Sylvain has
> >>>> attached his acpidump.
> >>>
> >>> Thanks.
> >>> According to the discussion in the bugzilla place, it doesn't seem we
> >>> have any other way to handle this at the moment.
> >>>
> >>> Acked-by: Aaron Lu <aaron.lu@intel.com>
> >>
> >> Thanks. So that only leaves Jani's remark:
> >>
> >>   > Nitpick, I'd prefer positively named variables, like enable_foo to avoid
> >>   > the double negative !disable_foo. enable_foo and !enable_foo read much
> >>   > better. But up to Aaron and friends.
> >>
> >> I personally believe that having the option named disable_backlight_sysfs_if
> >> is better here since I believe that things which are always enabled except
> >> on a few broken model laptops the option name should be disable_foo so
> >> that people can clearly see in /proc/cmdline / dmesg that the user is passing
> >> an option to disable something which is normally enabled.
> >
> > Fair enough.
> >
> >>
> >> As for the (!disabled) argument, the code in question here actually is:
> >>
> >> if (disabled)
> >> 	return 0;
> >>
> >> :)
> >>
> >> Still if people want me to change the option to a default-on
> >> enable_backlight_sysfs_if option I can do a v3...
> >
> > I'm not insisting.
> 
> Great, thanks :)
> 
> So I'm going to assume this v2 patch is ready for merging then, if anyone
> wants me to make any changes please let me know.

The v2 queued up for 4.2, thanks!


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.