From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chanwoo Choi Subject: Re: [PATCH v4] extcon: gpio: Add the support for Device tree bindings Date: Tue, 31 May 2016 23:34:48 +0900 Message-ID: References: <1464263265-20187-1-git-send-email-vreddytalla@nvidia.com> <20160527152934.GB12024@rob-hp-laptop> <574D32D7.2090902@samsung.com> <574D3EA7.9080907@samsung.com> Reply-To: cw00.choi-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Rob Herring Cc: Venkat Reddy Talla , MyungJoo Ham , Pawel Moll , Mark Rutland , Ian Campbell , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Kumar Gala , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Laxman Dewangan List-Id: devicetree@vger.kernel.org Hi Rob, On Tue, May 31, 2016 at 10:35 PM, Rob Herring wrote: > On Tue, May 31, 2016 at 2:35 AM, Chanwoo Choi = wrote: >> Hi Rob, >> >> On 2016=EB=85=84 05=EC=9B=94 31=EC=9D=BC 15:44, Chanwoo Choi wrote: >>> On 2016=EB=85=84 05=EC=9B=94 28=EC=9D=BC 00:29, Rob Herring wrote: >>>> On Thu, May 26, 2016 at 05:17:45PM +0530, Venkat Reddy Talla wrote= : >>>>> Add the support for Device tree bindings of extcon-gpio driver. >>>>> The extcon-gpio device tree node must include the both 'extcon-id= ' and >>>>> 'gpios' property. >>>> >>>> I think extcon bindings are a mess in general... >>>> >>>>> For example: >>>>> usb_cable: extcon-gpio-0 { >>>>> compatible =3D "extcon-gpio"; >>>>> extcon-id =3D ; >>>>> gpios =3D <&gpio6 1 GPIO_ACTIVE_HIGH>; >>>>> } >>>>> ta_cable: extcon-gpio-1 { >>>>> compatible =3D "extcon-gpio"; >>>>> extcon-id =3D ; >>>>> gpios =3D <&gpio3 2 GPIO_ACTIVE_LOW>; >>>>> debounce-ms =3D <50>; /* 50 millisecond */ >>>>> wakeup-source; >>>>> } >>>> >>>> This is all 1 logical connector, the USB connector. Why are you >>>> describing cables? Those are not part of the h/w and are dynamic. >>>> Describe this as a connector which is one thing (i.e. node). Use a >>>> compatible string that reflects the type of connector >>>> (usb-microab-connector), not the driver you want to use. Then defi= ne >>>> GPIO lines needed to provide state information like VBus, ID, char= ger >>>> modes and control lines like soft connect (D+ pullup enable), VBus >>>> enable, etc. >>> >>> You're right. The extcon-gpio driver will not use the "extcon-gpio"= raw compatible. >>> As you commented[1], the each connector will have the unique name t= o use the extcon-gpio.c driver. >>> [1] https://lkml.org/lkml/2015/10/21/906 >>> >>> >>> For example, >>> The extcon-gpio.c driver may have the different name including the = h/w information >>> according to the kind of external connector. >>> >>> static const struct of_device_id gpio_extcon_of_match[] =3D { >>> { >>> .compatible =3D "extcon-chg-sdp", /* SDP charger conn= ector */ >>> .data =3D EXTCON_CHG_SDP_DATA, >>> }, { >>> .compatible =3D "extcon-chg-dcp", /* DCP charger conn= ector */ >>> .data =3D EXTCON_CHG_DCP_DATA, >>> }, { >>> .compatible =3D "extcon-jack-microphone", /* Micropho= ne jack connector */ >>> .data =3D EXTCON_JACK_MICROPHONE_DATA, >>> }, { >>> .compatible =3D "extcon-disp-hdmi", /* HDMI connector= */ >>> .data =3D EXTCON_DISP_HDMI_DATA, >>> }, >>> ...... >>> }; >> >> I reply it again. >> >> The extcon-gpio.c is very similar with existing gpio_keys.c driver[1= ] >> [1] drivers/input/keyboard/gpio_keys.c > > There is a big difference in that each gpio-key is independent. The > only state is pressed or not. A USB connector has multiple pieces of > state information. You may be treating them independently, but I don'= t > think they should be. I think that is it not different because the EXTCON can only notify the= whether external connector is attached or detached such as gpio-key (pressed or= not). EXTCON don't handle the any additional state except for attached or det= ached. > >> The gpio_keys.c driver use the following style to support the device= -tree. >> It use the "gpio-keys" compatible and this dt node include the speci= fic >> 'key code' such as 'extcon-id =3D ;' > > This is state information about what is currently attached. The > analogy with gpio-keys would be multiple key codes on one gpio which > would be broken... I compared between 'gpis-keys' and ' extcon-gpio' driver as following: name | gpio-keys | extcon-gpio -----------------------------------------------------------------------= ---------------------- gpio | gpios =3D <> | extcon-gpio =3D <> -----------------------------------------------------------------------= ---------------------- type | linux,code =3D <> | extcon-id =3D <> -----------------------------------------------------------------------= ---------------------- key & | KEY_POWER | EXTCON_USB extcon id | KEY_VOLUME_UP | EXTCON_CHG_USB_SDP | KEY_VOLUME_DOWN | EXTCON_JACK_MICROPHONE | etc | etc -----------------------------------------------------------------------= ---------------------- state | pressed or not | attached or detached -----------------------------------------------------------------------= ---------------------- > >> >> gpio_keys { >> compatible =3D "gpio-keys"; >> >> power_key { >> gpios =3D <&gpx2 7 GPIO_ACTIVE_LOW>; >> linux,code =3D ; >> label =3D "power key"; >> debounce-interval =3D <10>; >> wakeup-source; >> }; >> }; >> >> If the extcon-gpio.c driver should have the separate compatible acco= rding to >> the kind of external connector, the list of compatible name of extco= n-gpio.c driver >> will be increased when new external connector is attached. > > So? Different h/w needs different compatible strings. > > But again, you are mixing describing the connector (only what is > soldered on a board) and state information (what is attached). Do not > put state information into DT (describe the gpio signals or chip that > provides the state information). > >> The extcon-gpio.c driver can separate the kind of external connector >> by using the 'extcon-id' property. > > This use of DT is just broken. Come up with another way. > > Rob Thanks, Chanwoo Choi -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html