On Sat, Jun 10, 2006 at 08:38:18AM +0800, Antonino A. Daplas wrote:
> Greg KH wrote:
> > On Fri, Jun 09, 2006 at 04:39:51PM +0800, Antonino A. Daplas wrote:
> >> Add sysfs attributes for binding and unbinding VT console drivers. The
> >> attributes are located in /sys/class/tty/console and are namely:
> >>
> >> A. backend - list registered drivers in the following format:
> >>
> >> "I C: Description"
> >
> > No, this violates the "one value per file" issue with sysfs. How do you
> > know you will not overflow the buffer passed to you?
>
> I was wondering about this. I just want a way to show what are the currently
> loaded drivers, so it's a read-only attribute. It's using snprintf (though
> I haven't added a check for possible overflows, should be a 2-liner). Maximum
> number of lines is 16, and there are examples of this rule-breakage in the
> current sysfs tree.
>
> /sys/class/usb_host/usb_hostx/device/pools
Ah, thanks for pointing this out. Those files should go to debugfs,
they do NOT belong in sysfs at all.
> Yes, none are valid excuses. Anyway, what would be the best way? I was
> considering creating another class for vt_console, but that would entail
> the creation of a new device major number just for this.
No, you don't need a major to create a new class in sysfs at all. Look
at usb_host for an example of that :)
And even if you did, we have loads of free major numbers now, it's not a
big deal to get a new one.
I vote for this, it would make things much easier.
> >> Where: I = ID number of the driver
> >> C = status of the driver which can be:
> >>
> >> S = system driver
> >> B = bound modular driver
> >> U = unbound modular driver
> >>
> >> Description - text description of the driver
> >>
> >> B. bind - binds a driver to the console layer
> >>
> >> echo <ID> > /sys/class/tty/console/bind
> >>
> >> C. unbind - unbinds a driver from the console layer
> >>
> >> echo <ID> > /sys/class/tty/console/unbind
> >>
> >> The tty layer does nothing to these attributes except create them and punt all
> >> requests to the VT layer.
> >
> > Why is this needed? What is wrong with the current scheme of binding
> > ttys to the console?
> >
>
> The binding part, maybe none, but that's still debatable. It's the unbinding
> feature that people are requesting. Note the longish threads on "the future
> of graphics subsystem". It would also ease the life of console driver
> developers, and it would stop people from pestering me on why they cannot unload
> their beloved framebuffer console and drivers and go back to VGA console.
Ok, I also read the 0/5 in this series which describes this in detail,
sorry for not seeing that (hint, cc: everyone on the series that one
too, so they get a bit of detail in the future.)
thanks,
greg k-h
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