Re: [PATCH v5 1/2] TTY: Add TTY slave enumeration support

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Sat, Jan 26, 2013 at 12:32:16AM +0000, Alan Cox wrote:
> > Or am I missing something big and major here?  How have people been
> > seeing and configuring their tty devices for the last 8+ years or so
> > since the 2.6.0 kernel was released with uevent support for tty
> > devices?
> 
> Minor more than major. The newer ACPI tries to begin to describe what
> is on the other end of serial busses being used for internal purposes.
> 
> Now there are several good reasons we want to know what is on the end
> of a port already that are not currently handled, and I have suggested
> a port "type" attribute would be useful (eg  unknown, modem, bluetooth,
> ax25, dcc, etc) so the kernel can help user space enumerate in user
> friendly fashion.

That's fine, just add a single attribute to the existing tty class
device, not a whole new class, which is what this code does.

> Where it gets slightly more tricky is that we are beginning to see
> systems where the firmware is describing
> 
> 	serial port (and power management)
> 	device behind port (and power management)
> 
> so there is a power management hierarchy involved.

Ick, that's going to get messy fast.  There's no hope they would switch
to a USB connection instead for these devices, could they?  That would
fix up most of these issues, and make the devices discoverable.

thanks,

greg k-h