Hi Mortiz, I'm not 100% into the problem to understand all cases. I'm putting on the table the point of view, mainly, of an user. If you say there are problems here or there I believe you. At the beginning, you did not say that this interface may introduce problems (and I'm interested in those problems since I implemented one and we are using it), but that you fear that it becomes the default (usually, being a default is a good thing). Since you and Alan are working on this for a long time, you can read each other mind, but I need a more verbose email to understand ^_^' Of course the interface must be safe, I totally agree. In order to make me understand what are the issues, can you list some of them? And expand your comment about MMIO. (I just did a dummy backport, and implemented that interface. So, I repeat myself: I do not have enough experience with this framework to understand all consequences, but I'm interested to know what are the risks behind this interface) On Friday, August 17, 2018 12:00:34 AM CEST Moritz Fischer wrote: > Hi Federico, > > On Thu, Aug 16, 2018 at 11:21:32PM +0200, Federico Vaga wrote: > > Hi, > > > > On Thursday, August 16, 2018 10:04:51 PM CEST Alan Tull wrote: > > > On Thu, Aug 16, 2018 at 1:59 PM, Moritz Fischer <mdf@xxxxxxxxxx> wrote: > > > > Hi Alan, > > > > > > Hi Moritz, > > > > > > > comments inline. While I see how this is useful, I have the > > > > suspicion that from the moment this gets merged vendor kernels > > > > will just default to use this ... > > > > > > Yeah, I have that suspicion as well. That's probably why I sat on > > > this and didn't upstream it for 2 years. But on the other hand, I > > > keep hearing of lots of cases of people implementing this > > > independently anyway. At least if it is debugfs, it makes it clear > > > that it's not intended for production use. > > > > I'm one of those guys who implemented this independently. > > We all have in one way or another ;) Most people on ARM run an out of tree > patch using devicetree overlays these days I hope rather than /dev/mem > and UIO ... or other vender solutions... > > > @Mortiz > > I do not see how this can be a bad thing (from what you wrote I guess you > > prefer another interface). Which interface to use depends on the use case. > > If you have this suspicion it's, I guess, because such interface it is > > extremely easy to use. > > What happens to a kernel driver doing MMIO with devices while you reload > the entire FPGA from userland? > > > @Alan > > DebugFS can be a first step, but I would go for a normal device in /dev at > > some point. I do not see why this should not be used in production > > I'm not against having a userland interface to reprogram the FPGA, the > Intel DFL code is a good example of a sensible one, doing so in a safe > manner. > > Ideally we'll get around to have a more generic interface, as we get > time to work on it. > > - Moritz
