From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [Gta04-owner] [PATCH 0/3] tty slave device support - version 3. Date: Thu, 07 May 2015 10:56:51 -0400 Message-ID: <554B7D33.602@hurleysoftware.com> References: <55492001.30806@hurleysoftware.com> <20150506092738.GB4508@amd> <554A03A7.2000504@hurleysoftware.com> <20150506123632.GA1764@leverpostej> <20150506141547.GB1764@leverpostej> <20150506171802.GE2974@leverpostej> 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: "Dr. H. Nikolaus Schaller" , Mark Rutland Cc: Pavel Machek , List for communicating with real GTA04 owners , NeilBrown , One Thousand Gnomes , Arnd Bergmann , Greg Kroah-Hartman , Sebastian Reichel , "grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" , Jiri Slaby , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org On 05/07/2015 08:46 AM, Dr. H. Nikolaus Schaller wrote: > So I don=E2=80=99t think that being able to control the slave is a co= mmon property > of all UART-slave connections. >=20 > BTW: the GPS chip we use is doing something without any instructions.= It starts > to send NMEA records right after power on. It would even be useful wi= th a unidirectional > connection from GPS to UART. Hence there are no commands that need to= be > sent through UART. Rather it just needs some GPIO to be activated or = powered down > when /dev/tty is opened/closed. In this example, the GPIO is a workaround for the lack of DTR. > So one could argue that in this real case (which we try to solve in a= n acceptable way > since 2 years) the fundamental/main interface (control command interf= ace) of this chip > is the power on/off line. And UART isn=E2=80=99t involved at all. Or = just as an =E2=80=9Cactivity detector=E2=80=9D. The indirect nature of control in this case only reflects the workaroun= d, not the underlying concept. Control is still derived from the UART stat= us. Both devicetree and tty/serial can already represent independent contro= l; what is proposed is a way to express dependent control, and in all case= s, that control stems directly from either the UART state itself or via commands sent over that interface. Any target not requiring UART involvement doesn't (and probably, should= n't) be expressed as a slave device. Regards, Peter Hurley -- 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