From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Date: Tue, 11 Jun 2019 10:28:51 +0000 Subject: Re: [PATCH 1/2] dt-bindings: pwm-backlight: Add 'max-brightness' property Message-Id: <20190611102851.GA16611@ulmo> MIME-Version: 1 Content-Type: multipart/mixed; boundary="5mCyUwZo2JvN/JJP" List-Id: References: <20190610233739.29477-1-mka@chromium.org> In-Reply-To: <20190610233739.29477-1-mka@chromium.org> To: Matthias Kaehlcke Cc: Lee Jones , Daniel Thompson , Jingoo Han , Jacek Anaszewski , Pavel Machek , Rob Herring , Mark Rutland , Bartlomiej Zolnierkiewicz , Enric Balletbo i Serra , dri-devel@lists.freedesktop.org, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org, Douglas Anderson , Brian Norris --5mCyUwZo2JvN/JJP Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 10, 2019 at 04:37:38PM -0700, Matthias Kaehlcke wrote: > Add an optional 'max-brightness' property, which is used to specify > the number of brightness levels (max-brightness + 1) when the node > has no 'brightness-levels' table. >=20 > Signed-off-by: Matthias Kaehlcke > --- > .../devicetree/bindings/leds/backlight/pwm-backlight.txt | 3 +++ > 1 file changed, 3 insertions(+) >=20 > diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlig= ht.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > index 64fa2fbd98c9..98f4ba626054 100644 > --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > @@ -27,6 +27,9 @@ Optional properties: > resolution pwm duty cycle can be used without > having to list out every possible value in t= he > brightness-level array. > + - max-brightness: Maximum brightness value. Used to specify the number= of > + brightness levels (max-brightness + 1) when the node > + has no 'brightness-levels' table. Back at the time when these bindings were defined we specifically didn't add this because it was deemed impractical. That is, no real hardware is actually capable of achieving useful results with a simplified description like this. Besides, we already have the num-interpolated-steps property which should allow you to achieve the same thing: brightness-levels =3D <0 255>; default-brightness-level =3D <1>; num-interpolated-steps =3D <255>; Though given the original discussion that we had around how backlight hardware behaves, that doesn't seem like a good choice. Thierry --5mCyUwZo2JvN/JJP Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAlz/gl4ACgkQ3SOs138+ s6GSfxAAwY+qUwKq+54LHTg+9GjvcE4Uq0lDCHIfRvxHcE9LkoP6hO+howgYknDN 8jhc8KUrHT4VgdE3gGokIwPssNaRzeEnGJ82WaIQ0s0PIhD1Vsa0gx81P+fDj4TT ByA5QlRiF1aaVDQLBlXDhTTjzl0xL/8/Q+gANrZVezWsDUBBCEwofvEQMoj0MJ+g NH+AdOPsjMZnY4QToqzPnEQ2WU3HrLB45MLKm+fxUdgEkN2h80tvjmXr5jgyBnQ1 /dk8aOxFteV0kyvDJt+ZprHTGFvp43hZ5uvQqTLVZyEiW3pyt4snu1jnv8p9GTEV C3lP1/U3Xh+y+1CuZ4RCykHYBh1dr1YFrkbtebcAFFFuAI+qtbdPEym7IDOjKHhb o9XwM7j4EOpLyoaWdOE4IbdPMCsoCyZzNQklw1CfS6F+8Ei6qbFUq2302/RTPcZv NlgAHTQ0Ngh0rLBW5GaUE/Tb0zb3GksiVAnILi/lk2u+BhFxB8KCK0GgCVHY7I81 iP+DiCXDciGi6r8+WkdFsz0577IntMoOVPqQ2OliC4snRnp6SJ6fJEAT5zAMB3id uc2LsElo8NT7VtTQzq6WRjtS2Yb+AexuVtpZDnwIWqO5U17Sdc9Li1YdV9s/p4eG Zbj2CZoWVjHVlv/7Fk4dY/ofFOPPcpgK/Aengy3NmXjIL4DxmcI= =qSIX -----END PGP SIGNATURE----- --5mCyUwZo2JvN/JJP--