Question on "embedded" classes

Question on "embedded" classes

[Luben Tuikov]

Hi,

I was wondering what the reason was for allowing
class and classdev to only be at level 3 and level
4 respectively of sysfs (/ is level 0)?

1) Some devices would not have any relevance
ouside the scope of the "parent" device.
2) "Hooking" them all at /sys/class/ level
would create quite a lot of symlinks (and with
cryptic names in order to reference the proper
"parent" device in the same directory).

E.g. Some devices, like SAS host adapters, have "devices
inside devices" and I'd like to represent this in
sysfs.

/sys/class/sas          (a class)
/sys/class/sas/ha0/     (a classdev)
/sys/class/sas/ha1/     (a classdev)

/sys/class/sas/ha0/device -> symlink to PCI device
/sys/class/sas/ha0/device_name    (text attribute)

/sys/class/sas/ha0/phys/     (a class)
/sys/class/sas/ha0/phys/0/   (a classdev)

etc.

Question: how does one "marry" the class to the classdev?

Or what is the alternative?

Thanks,
	Luben

Re: Question on "embedded" classes

[Greg KH]

On Mon, Jun 27, 2005 at 07:19:22PM -0400, Luben Tuikov wrote:
> Hi,
> 
> I was wondering what the reason was for allowing
> class and classdev to only be at level 3 and level
> 4 respectively of sysfs (/ is level 0)?
> 
> 1) Some devices would not have any relevance
> ouside the scope of the "parent" device.
> 2) "Hooking" them all at /sys/class/ level
> would create quite a lot of symlinks (and with
> cryptic names in order to reference the proper
> "parent" device in the same directory).
> 
> E.g. Some devices, like SAS host adapters, have "devices
> inside devices" and I'd like to represent this in
> sysfs.
> 
> /sys/class/sas          (a class)
> /sys/class/sas/ha0/     (a classdev)
> /sys/class/sas/ha1/     (a classdev)
> 
> /sys/class/sas/ha0/device -> symlink to PCI device
> /sys/class/sas/ha0/device_name    (text attribute)
> 
> /sys/class/sas/ha0/phys/     (a class)
> /sys/class/sas/ha0/phys/0/   (a classdev)

Nope, this is not allowed.

Classes are not allowed to have children classes.
class devices can not have children, be they class_device or a class.

That is the reason you are getting oopses :)

thanks,

greg k-h