[RFC] possible removal of omap-serial

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:

quoted

Hi,

On Thu, Mar 20, 2014 at 05:12:28PM -0700, Greg KH wrote:

quoted

On Thu, Mar 20, 2014 at 06:52:10PM -0500, Felipe Balbi wrote:

quoted

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.

greg k-h