From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH v2 1/2] leds: Add Intel Cherry Trail Whiskey Cove PMIC LEDs Date: Fri, 15 Feb 2019 00:03:07 +0100 Message-ID: <20190214230307.GA17358@amd> References: <20190212205901.13037-1-jekhor@gmail.com> <20190212205901.13037-2-jekhor@gmail.com> <1df39a63-533f-bb68-a056-a0241f148be9@redhat.com> <20190213230731.GA8557@amd> <42078a81-e32e-81b7-528f-d1adb60d31c3@redhat.com> <20190213233806.GA11867@amd> <562e2acd-a60a-2aea-4050-6d9414d23a4e@redhat.com> <20190214111423.GE6132@amd> <92cf09b8-726d-4f1b-94ba-368a66af2246@redhat.com> <2b6faaa5-b21e-a512-de7d-ca21be5045fc@gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="45Z9DzgjV8m4Oswq" Return-path: Content-Disposition: inline In-Reply-To: <2b6faaa5-b21e-a512-de7d-ca21be5045fc@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Jacek Anaszewski Cc: Hans de Goede , Yauhen Kharuzhy , linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org List-Id: linux-leds@vger.kernel.org --45Z9DzgjV8m4Oswq Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > >>>I suggest that we deal with this special case by adding 3 custom > >>>sysfs attributes: > >>> > >>>1) "mode" which when read, prints, e.g. : > >>>manual [on-when-charging] > >> > >>While this allows _user on console_ to control everything using echo, > >>it is not suitable for applications trying to control LEDs. > >> > >>As there's nothing special about the case here, I believe we should > >>have generic solution here. > >> > >>My preffered solution would be "hardware" trigger that leaves the LED > >>in hardware control. > > > >As you explained in the parts which I snipped, there are many > >devices which have a similar choice for a LED being under hw or > >user control. I can see how this looks like a trigger and how we > >could use the trigger API for this. > > > >I believe though, that if we implement a "virtual" (for lack of > >a better word) trigger for this, that this should be done in the > >LED core. I can envision this working like this: > > > >1) Add a: > > > >hw_control_set(struct led_classdev *led_cdev, bool enable_hw_control); >=20 > Please note that we have support for hw patterns in the pattern trigger. > (see how drivers/leds/leds-sc27xx-bltc.c makes use of it for its > breathing pattern). > We have also support for hw blinking in timer trigger via blink_set op. >=20 > In addition to that there is brightness_hw_changed sysfs attribute > with led_classdev_notify_brightness_hw_changed() LED API. >=20 > Couldn't they be used in concert to support the specific features > of the device in question? I believe main issue here is this: Hardware can automatically control the LED according to the charging status, or it can be used as normal software-controlled LED. I believe we should use trigger to select if hardware controls it or not (and then add driver-specific files to describe the details). Other proposal is in the mail thread, too. Best regards, Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --45Z9DzgjV8m4Oswq Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlxl86sACgkQMOfwapXb+vIVrwCfWOOXkUNNo1qHi9oaIcJFMEWH /W8AnRJZrracf/phzx/edwilQCQPKppD =yr9G -----END PGP SIGNATURE----- --45Z9DzgjV8m4Oswq--