Hi Hans, On Tuesday 14 Mar 2017 08:55:36 Hans Verkuil wrote: > On 03/14/2017 04:45 AM, Mauro Carvalho Chehab wrote: > > Hi Sakari, > > > > I started preparing a long argument about it, but gave up in favor of a > > simpler one. > > > > Em Mon, 13 Mar 2017 14:46:22 +0200 Sakari Ailus escreveu: > >> Drivers are written to support hardware, not particular use case. > > > > No, it is just the reverse: drivers and hardware are developed to > > support use cases. > > > > Btw, you should remember that the hardware is the full board, not just the > > SoC. In practice, the board do limit the use cases: several provide a > > single physical CSI connector, allowing just one sensor. > > > >>> This situation is there since 2009. If I remember well, you tried to > >>> write such generic plugin in the past, but never finished it, apparently > >>> because it is too complex. Others tried too over the years. > >> > >> I'd argue I know better what happened with that attempt than you do. I > >> had a prototype of a generic pipeline configuration library but due to > >> various reasons I haven't been able to continue working on that since > >> around 2012. > > ... > > > >>> The last trial was done by Jacek, trying to cover just the exynos4 > >>> driver. Yet, even such limited scope plugin was not good enough, as it > >>> was never merged upstream. Currently, there's no such plugins upstream. > >>> > >>> If we can't even merge a plugin that solves it for just *one* driver, > >>> I have no hope that we'll be able to do it for the generic case. > >> > >> I believe Jacek ceased to work on that plugin in his day job; other than > >> that, there are some matters left to be addressed in his latest patchset. > > > > The two above basically summaries the issue: the task of doing a generic > > plugin on userspace, even for a single driver is complex enough to > > not cover within a reasonable timeline. > > > > From 2009 to 2012, you were working on it, but didn't finish it. > > > > Apparently, nobody worked on it between 2013-2014 (but I may be wrong, as > > I didn't check when the generic plugin interface was added to libv4l). > > > > In the case of Jacek's work, the first patch I was able to find was > > > > written in Oct, 2014: > > https://patchwork.kernel.org/patch/5098111/ > > (not sure what happened with the version 1). > > > > The last e-mail about this subject was issued in Dec, 2016. > > > > In summary, you had this on your task for 3 years for an OMAP3 > > plugin (where you have a good expertise), and Jacek for 2 years, > > for Exynos 4, where he should also have a good knowledge. > > > > Yet, with all that efforts, no concrete results were achieved, as none > > of the plugins got merged. > > > > Even if they were merged, if we keep the same mean time to develop a > > libv4l plugin, that would mean that a plugin for i.MX6 could take 2-3 > > years to be developed. > > > > There's a clear message on it: > > - we shouldn't keep pushing for a solution via libv4l. > > Or: > - userspace plugin development had a very a low priority and > never got the attention it needed. > > I know that's *my* reason. I rarely if ever looked at it. I always assumed > Sakari and/or Laurent would look at it. If this reason is also valid for > Sakari and Laurent, then it is no wonder nothing has happened in all that > time. The reason is also valid for me. I'd really love to work on the userspace side, but I just can't find time at the moment. > We're all very driver-development-driven, and userspace gets very little > attention in general. So before just throwing in the towel we should take > a good look at the reasons why there has been little or no development: is > it because of fundamental design defects, or because nobody paid attention > to it? > > I strongly suspect it is the latter. > > In addition, I suspect end-users of these complex devices don't really care > about a plugin: they want full control and won't typically use generic > applications. If they would need support for that, we'd have seen much more > interest. The main reason for having a plugin is to simplify testing and > if this is going to be used on cheap hobbyist devkits. > > An additional complication is simply that it is hard to find fully supported > MC hardware. omap3 boards are hard to find these days, renesas boards are > not easy to get, freescale isn't the most popular either. Allwinner, > mediatek, amlogic, broadcom and qualcomm all have closed source > implementations or no implementation at all. > > I know it took me a very long time before I had a working omap3. > > So I am not at all surprised that little progress has been made. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
