On Thu, Mar 20, 2014 at 09:45:42PM -0500, Robert Nelson wrote: > On Thu, Mar 20, 2014 at 9:36 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Mar 20, 2014 at 08:37:29PM -0500, Felipe Balbi wrote: > >> On Thu, Mar 20, 2014 at 08:35:57PM -0500, Felipe Balbi wrote: > >> > Hi, > >> > > >> > On Thu, Mar 20, 2014 at 05:12:28PM -0700, Greg KH wrote: > >> > > On Thu, Mar 20, 2014 at 06:52:10PM -0500, Felipe Balbi wrote: > >> > > > Hi folks, > >> > > > > >> > > > I've been toying with the idea of removing > >> > > > drivers/tty/serial/omap-serial.c since that's, to put it bluntly, an > >> > > > ungly copy of 8250 driver. > >> > > > > >> > > > The original concern was wrt suspend/resume but I think it'd be a far > >> > > > better approach to implement runtime PM in 8250 and write a rather small > >> > > > 8250-omap.c glue (much like 8250-acorn.c or 8250-dw.c) just to get the > >> > > > OMAP-specific details out of the way. > >> > > > > >> > > > The question I have is: omap-serial.c calls the serial devnodes ttyO\d, > >> > > > instead of ttyS\d so removing omap-serial.c would have a direct impact > >> > > > in userland. I wonder if it's an acceptable "regression" considering > >> > > > we'd be able to reuse 8250 gaining proper Flow Control support, proper > >> > > > DMA support, years and years of bug-fixes, etc. > >> > > > >> > > Breaking device node names is a contentious issue for serial ports, I > >> > > don't think you can do that :( > >> > > >> > would an upstream udev rule creating a symbolic link from ttyO to ttyS > >> > be enough ? > >> > > >> > I didn't test this yet but I guess this is enough (?) > >> > > >> > KERNEL=="ttyO[0-9]", GROUP="dialout", SYMLINK+="ttyS" > >> > >> or actually it should be to other way around, ttyS would be the real > >> device: > >> > >> KERNEL=="ttyS[0-9]", GROUP="dialout", SYMLINK+="ttyO" > > > > As udev rules don't ship with the kernel, this might be tough to do :( > > > > Might be easier to make the 8250 driver handle different "names" like > > Alan said. I'll see if I find a way to avoid that or at least see if we find any other way of creating a symlink... In any case, just switching back to 8250, even if just maintaining ttyO name, is already a big benefit. > On the support side, I'm not looking forward to this for beagle/panda > users. We've already converted them once from ttySx -> ttyOx back in > 2.6.33/2.6.34? days. That was an irc/email/u-boot/kernel nightmare... that's exactly why we're talking about ways to maintain backwards compatibility here. But I'm more interested in finding a way to switch over to ttyS and have a symlink to ttyO, that way a simple debootstrap (or any other ARM distro minimal rootfs) would work out of the box, without any changes, just like in "normal" systems. -- balbi
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