Re: New hotplug interface is not working right for me

[Hannes Reinecke <hare@suse.de>]

Kay Sievers wrote:
> On Thu, 2005-03-10 at 22:45 -0800, Greg KH wrote:
>>On Fri, Mar 11, 2005 at 01:04:05AM -0500, Eric S. Raymond wrote:
>>>Greg KH <greg@kroah.com>:
>>>>On Fri, Mar 11, 2005 at 12:20:54AM -0500, Eric S. Raymond wrote:
>>>>>Greg KH <greg@kroah.com>:
>>>>>>>The problem appears to be that whatever thread of control is creating 
>>>>>>>the /dev/ttyUSB* node is running asynchronously with the hotplug
>>>>>>>script and does not reliably (or even usually) create it before the
>>>>>>>gpsd instance gets spawned and goes looking for the node.
>>>>>>Then use the /etc/dev.d/ interface instead.  That requires udev and a
>>>>>>2.6 kernel, but is the only way you can know exactly when the /dev entry
>>>>>>is created.
>>>>>Where is this documented?
>>>>In the udev documentation and a simple google search brings it up.
>>>>
>>>>>Even if the /etc/dev.d/ interface works, that doesn't really make it
>>>>>acceptable that the /etc/hotplug.d/ interface is broken.  There is some
>>>>>locking that ought to be happening and isn't.
>>>>The interface is not broken, you are trying to trigger off of two
>>>>different hotplug events (one when the device appears, and a different
>>>>one when the device node is to be created.)
>>>If it's not broken, then it's not documented either.
>>You are watching for the wrong hotplug event, how can we document that?
>>:)
> 
> If the hotplug helper in /proc/sys/kernel/hotplug is set
> to /sbin/udevsend, what all major distributions seems to do today, than
> there is nearly no difference between /etc/hotplug.d/ and /etc/dev.d/.
True. Especially since hotplug.d is _always_ called after dev.d.
Having them in seperate directories just adds to the maintenance overhead.
> Yeah, I'm all for doing this with udev rules. It is already working on
> my box. We just need to agree if and how we should do that. The plan is
> to add hotplug scripts with udev rules and execute scripts based on the
> same rule logic we use to name the device node.
> 
> Your hook into hotplug with a udev rule would look like this:
>   ACTION="add", SYSFS{vendor}="GPS", SYSFS{product}="0815", NAME="gps", HOTPLUG="/usr/bin/gps-something"
> 
And that would be really nice.
Then we would have a truly fine-grained selection for which devices we
actually need to call scripts.
Booting with full event replay is slow enough as it is, any speed-up is
greatly welcome.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke			hare@suse.de
SuSE Linux AG				S390 & zSeries
Maxfeldstraße 5				+49 911 74053 688
90409 Nürnberg				http://www.suse.de


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