libusual interface [was Re: libusual and ub]

[Jeremy Katz]

On Thu, 2005-12-15 at 00:21 -0800, Pete Zaitcev wrote:
> On Thu, 15 Dec 2005 00:37:41 -0500, Bill Nottingham <notting at redhat.com> wrote:
> 
> > If you aren't using libusual to load the modules (installer), you have to
> > hardcode which module to load somewhere... Jeremy was sending me a (bad :) )
> > patch for this just the other day... with the ids in the module, you just
> > use the modalias.

Hey, to be fair, my patch was just probing for the devices once ub
already got loaded.  I ignored the question of "how does ub get loaded"
since I can guarantee that it happens in anaconda.

> Suddenly, the problem came into focus. I wish one of you cc:-ed me on it.
> Like I mentioned previously, when libusual is in effect, modprobing
> backend drivers makes no sense. With that in mind, I do not see a
> fundamental problem. We did have an explicit call to modprobe usb-storage.
> So now we would have something like 'modprobe libusual bias="ub"'.
> Is there a problem with passing of arguments?

With libusual built-in as davej currently has it, it becomes a little
bit harder because we don't want to rely on people passing kernel
arguments (... history has shown they don't, look back at the fiascos
with ramsdisk_size over the years).  So if we're going to build libusual
in statically, having the sysfs method to change the bias becomes
incredibly important (... as then I can just write to the file from the
loader and not worry about it)

> > You still get a USB hotplug event for the USB device, with the modalias,
> > etc. Obviously, running modprobe with that won't load anything, and
> > libusual has already claimed the device.
> 
> Have you actually tried it? Loads like a charm here, with 2.6.14-1.1740_FC5
> RPM, as it should. This is the scenario:
>  - Since we build with libusual static, there is no hotplug event.
>    module.alias is not involved.
>  - libusual gets ->probe
>  - libusual loads the driver (if not loaded)

libusual loading the driver is the tricky part here.  It works fine on
an installed system.  The installer is a little trickier because we
don't provide all of the same hotplug module loading stuff.  At the same
time, if I load ub in the loader, the right thing seems to happen, so it
doesn't actually cause me much in the way of concern.

Jeremy