[issue1616] hotplug notification

[Alex Hornung (via DragonFly issue tracker)]

Alex Hornung <ahornung at gmail.com> added the comment:

in devfs_alias_create(), you are notifying hotplug about the attach of the 
underlying device and not the alias. As such, if there was an alias such as 
serno/00001 for da0, you'd get two attach notices for da0 and none for 
serno/00001.
devfs links are no cdev_t, they are synthetic devfs nodes. The name that 
should be passed to hotplug at this point is the function parameter name_orig.

I don't know how you want to handle that, but I don't think synthesizing a 
cdev_t just to pass the name and/or type to hotplug is a good idea. You could 
pass in this case both the underlying cdev_t (which is what you are doing 
now, 'target') and the name of the link/alias.

Another option could be to pass devfs nodes to hotplug, which contain a lot 
more information than the cdev_t, but that causes a number of problems:
- you'd need to acquire a lock (and also release it) for every node you use
- devfs would not be well encapsulated anymore
- for links and aliases you would need to use a function to get the full path, 
as each node only stores its name; for this you would just iterate up to the 
root node across ->parent elements, and stashsing the nodes. Then, just walk 
through that stash in reverse order, putting together the path.

In any case, I'm more inclined to the solution of creating some
struct hotplug_device {
     cdev_t dev;
     char *name;
};
or similar. This will make it much easier to add new information/options in 
the future.

Cheers,
Alex Hornung

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assignedto:  -> alexh
nosy: +alexh
status: unread -> chatting

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