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Date:   Mon, 9 Jan 2023 08:04:08 +0100
From:   Stephen Kitt <steve@sk2.org>
To:     Sam Ravnborg <sam@ravnborg.org>
Cc:     Sam Ravnborg via B4 Submission Endpoint 
        <devnull+sam.ravnborg.org@kernel.org>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        linux-staging@lists.linux.dev,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Helge Deller <deller@gmx.de>, Lee Jones <lee@kernel.org>,
        Miguel Ojeda <ojeda@kernel.org>,
        Antonino Daplas <adaplas@gmail.com>,
        linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Robin van der Gracht <robin@protonic.nl>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Jingoo Han <jingoohan1@gmail.com>,
        linuxppc-dev@lists.ozlabs.org,
        Claudiu Beznea <claudiu.beznea@microchip.com>
Subject: Re: [PATCH 09/15] staging: fbtft: fb_ssd1351.c: Introduce
 backlight_is_blank()
Message-ID: <20230109080408.318b9188@heffalump.sk2.org>
In-Reply-To: <Y7sntztwrNqw41+i@ravnborg.org>
References: <20230107-sam-video-backlight-drop-fb_blank-v1-0-1bd9bafb351f@ravnborg.org>
        <20230107-sam-video-backlight-drop-fb_blank-v1-9-1bd9bafb351f@ravnborg.org>
        <20230108202817.7890f85c@heffalump.sk2.org>
        <Y7sntztwrNqw41+i@ravnborg.org>
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Hi Sam,

On Sun, 8 Jan 2023 21:29:43 +0100, Sam Ravnborg <sam@ravnborg.org> wrote:
> On Sun, Jan 08, 2023 at 08:28:17PM +0100, Stephen Kitt wrote:
> > On Sat, 07 Jan 2023 19:26:23 +0100, Sam Ravnborg via B4 Submission
> > Endpoint <devnull+sam.ravnborg.org@kernel.org> wrote:
> >  =20
> > > From: Sam Ravnborg <sam@ravnborg.org>
> > >=20
> > > Avoiding direct access to backlight_properties.props.
> > >=20
> > > Access to the deprecated props.fb_blank replaced by
> > > backlight_is_blank(). Access to props.power is dropped - it was only
> > > used for debug.
> > >=20
> > > Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> > > Cc: Stephen Kitt <steve@sk2.org>
> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > Cc: Daniel Thompson <daniel.thompson@linaro.org>
> > > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > > Cc: linux-fbdev@vger.kernel.org
> > > ---
> > >  drivers/staging/fbtft/fb_ssd1351.c | 9 +++------
> > >  1 file changed, 3 insertions(+), 6 deletions(-)
> > >=20
> > > diff --git a/drivers/staging/fbtft/fb_ssd1351.c
> > > b/drivers/staging/fbtft/fb_ssd1351.c index b8d55aa8c5c7..995fbd2f3dc6
> > > 100644 --- a/drivers/staging/fbtft/fb_ssd1351.c
> > > +++ b/drivers/staging/fbtft/fb_ssd1351.c
> > > @@ -190,15 +190,12 @@ static struct fbtft_display display =3D {
> > >  static int update_onboard_backlight(struct backlight_device *bd)
> > >  {
> > >  	struct fbtft_par *par =3D bl_get_data(bd);
> > > -	bool on;
> > > +	bool blank =3D backlight_is_blank(bd);
> > > =20
> > > -	fbtft_par_dbg(DEBUG_BACKLIGHT, par,
> > > -		      "%s: power=3D%d, fb_blank=3D%d\n",
> > > -		      __func__, bd->props.power, bd->props.fb_blank);
> > > +	fbtft_par_dbg(DEBUG_BACKLIGHT, par, "%s: blank=3D%d\n", __func__,
> > > blank);=20
> > > -	on =3D !backlight_is_blank(bd);
> > >  	/* Onboard backlight connected to GPIO0 on SSD1351, GPIO1
> > > unused */
> > > -	write_reg(par, 0xB5, on ? 0x03 : 0x02);
> > > +	write_reg(par, 0xB5, !blank ? 0x03 : 0x02);
> > > =20
> > >  	return 0;
> > >  }
> > >=20
> > > --=20
> > > 2.34.1 =20
> >=20
> > For debugging purposes here, would there be any point in logging
> > props.state? As in
> >=20
> >         fbtft_par_dbg(DEBUG_BACKLIGHT, par,
> > -                     "%s: power=3D%d, fb_blank=3D%d\n",
> > -                     __func__, bd->props.power, bd->props.fb_blank);
> > +                     "%s: power=3D%d, state=3D%u\n",
> > +                     __func__, bd->props.power, bd->props.state); =20
>=20
> Thanks for the suggestion - and the reviews!
>=20
> I was tempted to just remove the debugging.
> If we require debugging, then this could be added in the backlight core,
> thus everyone would benefit from it.
>=20
> The solution above avoid any direct use of backlight_properties
> which I consider a layer violation outside the backlight core.
> (We cannot avoid it today with the current interface - but we can
> minimize it).

Ah yes, ideally backlight_properties should be viewed as an opaque structur=
e,
that makes sense.

Regards,

Stephen

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