From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Denk Subject: Re: [CXP][RFC] Pick RTDM for the common kernel interface MIME-Version: 1.0 Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 8bit In-reply-to: <87pn3mzxeh.fsf@xenomai.org> References: <87pn3mzxeh.fsf@xenomai.org> Date: Mon, 14 Dec 2020 08:29:33 +0100 Message-ID: <439019.1607930973@gemini.denx.de> List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum , Philippe Gerum via Xenomai Dear Philippe, In message <87pn3mzxeh.fsf@xenomai.org> you wrote: > > PROPOSAL: Adopt a large subset of the current RTDM specification as > the common kernel interface defined by the CXP. The exact set of RTDM > services which should be retained in the CXP implementation must be > discussed further. > > As a consequence, Xenomai 4 would provide a RTDM layer based on the EVL > core interface internally, which would preserve the driver taxonomy > ("named" / "protocol") and registration model inherited from its Xenomai > 3.x counterpart. RTDM is a complex story. Once upon a time it served a number of important purposes; even providing a common driver interface for Xenomai and PREEMPT_RT (search for Xenomai/SOLO if you cannot remember). It may have beennecessary, but I have to admit that I am not 100% happy with it either. I have seen way toomany situations where the need to hava RTDM drivers for RT use caused a fork from the mainline Linux drivers, resulting in bitrot and lots of frustration becuase we had to deal with problems that were long fixed in the upstream drivers, while theRTDM counterparts received basically no maintenance. Yes, I agree to adapt a subeset of RTDM as a common kernel interface. But it should be clear that this is mostly to allow re-use of existing code and to easy migration. Whenever we run into problems with that, we should not look back too long but rather focus on a new, clean and efficient (and easy to maintain) design. Having RT capable drivers in mainline would be much, much better. So ACK. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de "There is such a fine line between genius and stupidity." - David St. Hubbins, "Spinal Tap"