Re: Udevstart & udevtrigger

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On Mon, Sep 1, 2008 at 16:44, Francesco RUNDO <francesco.rundo@xxxxxx> wrote:
> My name is Francesco Rundo and I work porting Linux (kernel, device drivers,
> etc..) for embedded system.
>
> I've a question about udev, in particular way, I need to get some info about
> udevstart and udevtrigger.
>
> In order to improve the boot speed, I've removed in my udev init scripts the
> tool udevstart. Basically, in my udev init scripts (which start firstly in
> the user space boot sequence) there are in order:
> 1) some operation on /dev  with manually creation of some  devices;
> 2) udevstart call;
> 3) starting of udevd;
> 4) udevtrigger call;
> 5) udevsettle call;
> After that, the common services will be initialized: ssh, D-bus, HAL, Lirc,
> etc...;
>
> I've noted that this sequence is used in different Linux distribution for
> embedded system.
>
> As far as I know, the tool "udevstart" has the target to populate initial
> device directoty (/dev). It walks trough the sysfs device tree and calls
> udev (daemon) to create the nodes for every valid device found. It is used
> to fill the initial empty device directory with nodes for all devices
> currently available. Is it right ?
>
> Now, I know that "udevtrigger"  replies the uevents generated by system
> coldplug of the devices (passing the info to the udev daemon) while
> udevsettle waits watching the udev event queue and exits if all current
> events are handled. Is it right ?
>
> By taking into account what above mentioned, I've removed from udev starting
> script the tool "udevstart" which needs a lot of time to populate the device
> (In my kernel config, I've a lot of device included in the kernel ) and I've
> managed udev only with udevtrigger and udevsettle. In this way, the device
> creation under /dev will be made by udevtrigger. I've saved 3/4 sec of boot
> time!!
>
> Finally, I've to say that in some web site I've noted that some Linux
> distribution were using this approach. Also the initNG project suggests to
> remove udevstart using only udevtrigger & udevsettle. Please, see
> http://www.initng.org/wiki/udevstart for more detail.
>
> Now the question is:
> Is it right to remove udevstart using only udevtrigger ?
> Are there some funcionality-restrictions in the udev if I don't use
> udevstart ?
> Is it true that starting from udev-117 udevstart will not be delivered ?
> In my distribution, we are aligned to udev-116

Udevstart is obsolete and does not exist anymore. It was replaced, and
is not installed since udev 082:
  http://git.kernel.org/?p=linux/hotplug/udev.git;a=commit;h=c233b59baaabe55a8f99dc37c4ee9011b85f8917

Kay
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