On 2019-03-29, Corey Minyard <miny...@acm.org> wrote: > On Thu, Mar 28, 2019 at 12:39:12PM -0700, H. Peter Anvin wrote: > >> Dumb question: this is basically a pty on steroids. Wouldn't this be >> better done by enhancing the pty devices?
I proposed doing that several years ago, and offered to start working on it if there was a decent chance it would be accepted into the tree. I got no response. > I did look at that, but it would be pretty invasive to pty. There's > no modem control stuff, none of the other special serial ioctls. > And the locking in this driver is fairly strange because you have > two serial ports looking at each other's data for modem control. > But that might not be a big deal. > > Adding the speed simulation to ptys would also be really strange. > That's not a deal-breaker, I suppose, but it's not much of a serial > port simulation without it. My goal wasn't really to simulate two serial ports with a null-mode cable in-between, so the speed simluaiton wasn't on my list. my goal was to provide a way to implement a serial port in userspace by attaching an application to the master end of a pty. The pty(7) man page states "The slave end of the pseudoterminal provides an interface that behaves exactly like a classical terminal." But, we all know that's a pretty big lie: the pty slave end implements only a small subset of a "classical termial" device, and there are all sorts of applications that expect to talk to a serial port which fail miserably when connected to a pty. -- Grant Edwards grant.b.edwards Yow! I had a lease on an at OEDIPUS COMPLEX back in gmail.com '81 ...