Re: [PATCH] add transport class symlink to device object

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Sun, Aug 14, 2005 at 04:02:31PM +0100, Matthew Wilcox wrote:
> On Sat, Aug 13, 2005 at 02:39:56PM -0700, Greg KH wrote:
> > Heh, I already have a patch like this pending for 2.6.14 at:
> > 	http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/gregkh-01-driver/driver-link-device-and-class.patch
> 
> Last time I tried to do something like this, it fell over with
> multi-function serial ports.  Look at this example:
> 
> # ls -l /sys/class/tty/ttyS*/device | cut -c40-
> /sys/class/tty/ttyS0/device -> ../../../devices/parisc/0/0:0/pci0000:00/0000:00:04.0
> /sys/class/tty/ttyS1/device -> ../../../devices/parisc/0/0:0/pci0000:00/0000:00:04.0
> /sys/class/tty/ttyS2/device -> ../../../devices/parisc/0/0:0/pci0000:00/0000:00:04.0
> /sys/class/tty/ttyS3/device -> ../../../devices/parisc/0/0:0/pci0000:00/0000:00:05.0
> /sys/class/tty/ttyS4/device -> ../../../devices/parisc/0/0:0/pci0000:00/0000:00:05.0
> 
> Adding the reverse links gets you three links in the 0000:00:04.0
> directory all called 'tty' (or 'class:tty', whatever), each pointing to
> a different place.  This doesn't happen for scsi devices as the class is
> attached to the scsi_dev, not the pci_dev.  I think the tty subsystem
> needs to be modified to add tty_devs as subdevices of the pci_dev.

Eww.  Do you really want one struct device per tty with all the
memory each one eats?

If that's really what you want you need to talk to Alan and not me.
Alan looks after tty level stuff, I look after serial level stuff.
The above is a tty level issue not a serial level issue.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core