Re: [PATCH, RFC] wake up from a serial port

[Guennadi Liakhovetski <g.liakhovetski@gmx.de>]

On Mon, 13 Aug 2007, Scott Wood wrote:

> Guennadi Liakhovetski wrote:
> > 
> > # ls -l /sys/devices/platform/serial8250.0/tty*
> > lrwxrwxrwx 1 root root 0 Aug 13 22:05
> > /sys/devices/platform/serial8250.0/tty:ttyS0 -> ../../../class/tty/ttyS0
> > lrwxrwxrwx 1 root root 0 Aug 13 22:05
> > /sys/devices/platform/serial8250.0/tty:ttyS1 -> ../../../class/tty/ttyS1
> > 
> > And placing some wakeup file under the class/tty/ directory doesn't seem
> > very consistent with the current policy - until now they only live under
> > devices/... (Greg added to cc:).
> 
> Hmm... I'd assumed each port would have its own device directory.  Would
> anything break horribly if it were changed so that each tty:ttySx is a
> directory, which contains both a wakeup file and the symlink?

Yeah, I'd love to know the answer too:-) As you see, atm it is one 
platform device as defined in arch/powerpc/kernel/legacy_serial.c:

static struct platform_device serial_device = {
	.name	= "serial8250",
	.id	= PLAT8250_DEV_PLATFORM,
	.dev	= {
		.platform_data = legacy_serial_ports,
	},
};

with a list of ports in platform data:

static struct plat_serial8250_port legacy_serial_ports[MAX_LEGACY_SERIAL_PORTS+1];

Hence one device directory. Same on a PC

$ ls -l /sys/devices/platform/serial8250/tty*
lrwxrwxrwx  1 root root 0 Aug 13 23:10 /sys/devices/platform/serial8250/tty:ttyS0 -> ../../../class/tty/ttyS0
lrwxrwxrwx  1 root root 0 Aug 13 23:10 /sys/devices/platform/serial8250/tty:ttyS1 -> ../../../class/tty/ttyS1
lrwxrwxrwx  1 root root 0 Aug 13 23:10 /sys/devices/platform/serial8250/tty:ttyS2 -> ../../../class/tty/ttyS2
lrwxrwxrwx  1 root root 0 Aug 13 23:10 /sys/devices/platform/serial8250/tty:ttyS3 -> ../../../class/tty/ttyS3

> You should get the interrupt, but not until after the PM code enables IRQs.
> Are you saying that the interrupt handler runs before then?

Great, it is working correctly then! Don't think the ISR runs return from 
PM, no.

Thanks
Guennadi
---
Guennadi Liakhovetski