Re: /sbin/hotplug invocation for USB devices in 2.5.40

[David Brownell <david-b@pacbell.net>]

Patrick Mochel wrote:
>>>Now I know this overloads the existing DEVICE usage for USB devices, but
>>>I think we can determine what do properly (basically just test for
>>>DEVFS, and if it's not set, then we are looking at the driverfs entry
>>>for the device.)
>>
>>I'd rather see these changes:
>>
>>   - This new parameter to every (!!) hotplug event gets renamed to
>>     KFS_DEVICE (assuming that's the new driverfs name).
> 
> 
> What about DEVPATH, since that's what it is, right?

Well, it's different from usb_device->devpath ... devpath is just
one component of the KFS path.  One that's repeated because of
that requirement that names assigned by a bus be unique across
the whole system, making it easier to automate that symlinking. :)

It's not the only filesystem path used to access the device.
Would using KFS_DEVICE really be a problem?



>>By the way, what's the cost of a driverfs attribute on a 'struct device'?
>>Each USB device now has over a dozen of them.
> 
> 
> 32 bytes/attribute + size of the function. But, attributes are reused 
> across devices, so the total data cost is 32 x ~16 = 512. 

"Reused" meaning shared attributes like "name" and "power", I guess.

USB devices have at least one interface, and each will have six attributes
(including name+power).  So 32 x ~24 = 768 bytes minimum, on top of other
costs. These start to add up.

- Dave






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