On Tue, Aug 04, 2020 at 09:56:00PM +0200, Sam Ravnborg wrote:
> Hi Daniel et al.
> On Tue, Aug 04, 2020 at 06:43:30PM +0200, daniel@xxxxxxxx wrote:
> > On Sun, Aug 02, 2020 at 01:06:17PM +0200, Sam Ravnborg wrote:
> > > Add get and set operations to incapsualte access to backlight properties.
> > >
> > > One easy win is that the get/set operatiosn can be used when backlight
> > > is not included in the configuration, resulting in simpler code with
> > > less ifdef's and thus more readable code.
> > >
> > > The set/get methods hides some of the confusing power states, limiting
> > > the power state to either ON or OFF for the drivers.
> > >
> > > Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> > > Cc: Lee Jones <lee.jones@xxxxxxxxxx>
> > > Cc: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
> > > Cc: Jingoo Han <jingoohan1@xxxxxxxxx>
> > > ---
> > > include/linux/backlight.h | 72 +++++++++++++++++++++++++++++++++++++++
> > > 1 file changed, 72 insertions(+)
> > >
> > > diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> > > index d683c053ec09..882ceea45ace 100644
> > > --- a/include/linux/backlight.h
> > > +++ b/include/linux/backlight.h
> > > @@ -474,6 +474,78 @@ static inline int backlight_get_brightness(const struct backlight_device *bd)
> > > return bd->props.brightness;
> > > }
> > >
> > > +/**
> > > + * backlight_get_actual_brightness - Returns the actual brightness
> > > + *
> > > + * On failure a negative error code is returned.
> > > + */
> > > +static inline int backlight_get_actual_brightness(struct backlight_device *bd)
> > > +{
> > > + if (bd && bd->ops && bd->ops->get_brightness)
> > > + return bd->ops->get_brightness(bd);
> > > + else
> > > + return -EINVAL;
> > > +}
> > > +
> > > +/**
> > > + * backlight_get_max_brightness - Returns maximum brightness
> > > + *
> > > + * This helper operation is preferred over direct access to
> > > + * &backlight_properties.max_brightness
> > > + *
> > > + * Returns 0 if backlight_device is NULL
> > > + */
> > > +
> > > +static inline int backlight_get_max_brightness(const struct backlight_device *bd)
> > > +{
> > > + if (bd)
> > > + return bd->props.max_brightness;
> > > + else
> > > + return 0;
> > > +}
> > > +
> > > +/**
> > > + * backlight_set_brightness - Set the brightness to the specified value
> > > + *
> > > + * This helper operation is preferred over direct assignment to
> > > + * &backlight_properties.brightness.
> > > + *
> > > + * If backlight_device is NULL then silently exit.
> > > + */
> > > +static inline void backlight_set_brightness(struct backlight_device *bd, int brightness)
> > > +{
> > > + if (bd)
> > > + bd->props.brightness = brightness;
> >
> > Looking at the drivers I think including a call to backlight_update_status
> > would simplify a lot of code.
> >
> > > +}
> > > +
> > > +/**
> > > + * backlight_set_power_on - Set power state to ON.
> > > + *
> > > + * This helper operation is preferred over direct assignment to
> > > + * backlight_properties.power.
> > > + *
> > > + * If backlight_device is NULL then silently exit.
> > > + */
> > > +static inline void backlight_set_power_on(struct backlight_device *bd)
> > > +{
> > > + if (bd)
> > > + bd->props.power = FB_BLANK_UNBLANK;
> > > +}
> > > +
> > > +/**
> > > + * backlight_set_power_off - Set power state to OFF.
> > > + *
> > > + * This helper operation is preferred over direct assignment to
> > > + * backlight_properties.power.
> > > + *
> > > + * If backlight_device is NULL then silently exit.
> > > + */
> > > +static inline void backlight_set_power_off(struct backlight_device *bd)
> >
> > I'm not clear why we need these two above? I thought the long-term plan is
> > only use backlight_enable/disable and then remove the tri-state power
> > handling once everyone is converted over?
> >
> > Or maybe I'm just confused about the goal here ...
>
> My TODO for v2:
> - Check all get_brightness implmentations.
> Using backlight_get_brightness is wrong - find a better way
> Check that they do return the actual brightness and not just the copy
> from the backlight core
Well it's only for the get_brigthness callback where I think this is
problemantic. In update_state callback I think it's a good helper.
> - Get rid of all uses of power_on/off - this is just another way to
> disable backlight - so be explicit about it
> - Consolidate the backlight_set_brightness(); backlight_update() pattern
> to a helper
> - Look into a mipi helper for backlight
Imo perfectly fine to leave that out for some todo, otherwise this will
get huge.
> - Consider if we can change the backlight core to use an u32 for
> brightness
> - Take a look at Daniels rambling about drm_connector and backlight
Also something we can postpone I think. We can still used devm_ together
with a refcounted backlight (like we do with devm_drm_dev_alloc), and my
gut feel says refcounted backlight is probably the way to go eventually.
But also, we've been talking about drm_connector->panel for years, there's
no rush at all.
> - Convert some platform backlight drivers to updated interface - to verify
> that they do not add new demends
>
> The above should address feedback from Daniel etc. Thanks!
> No promises when I get time to do it - this list was mostly
> to help myself so I did not forget.
Sounds all good to me, and thanks for doing all this work!
Cheers, Daniel
>
> Note: My ISP blocked my attempt to reply to PATCH 0 - so I replied to
> this with the TODO list.
>
> Sam
>
>
> > -Daniel
> >
> > > +{
> > > + if (bd)
> > > + bd->props.power = FB_BLANK_POWERDOWN;
> > > +}
> > > +
> > > struct backlight_device *
> > > backlight_device_register(const char *name, struct device *dev, void *devdata,
> > > const struct backlight_ops *ops,
> > > --
> > > 2.25.1
> > >
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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