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From: John Baldwin <jhb@freebsd.org>
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Date: Fri, 7 Mar 2008 08:24:55 -0500
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Cc: =?utf-8?q?Jean-S=C3=A9bastien_P=C3=A9dron?= <dumbbell@freebsd.org>
Subject: Re: sysctl: good practices and how to deprecate a node
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On Friday 07 March 2008 05:11:17 am Jean-S=C3=A9bastien P=C3=A9dron wrote:
> Hello,
>
> I'm currently working again on the Synaptics Touchpad support[1] in psm(4=
).
>
> The enable_synaptics() probe function adds a subtree to "hw.psm"; I
> didn't changed its behaviour for now. This subtree is created only if:
>     o  "hw.psm.synaptics_support" is true
>     o  no previous probe function "took" the device.
> If the function doesn't find a Synaptics touchpad, the tree is left
> created.
>
> First, is enable_synaptics() the right place to add this subtree
> (compared to a "globally" created tree, like "hw.psm")?

Sure.

> If enable_synaptics() is the way to go, should it be always created if
> "hw.psm.synaptics_support" is true, even if no touchpad is found? Or
> only when the touchpad is detected?=20

Probably only if you have an actual touchpad.

> In psmsoftintr(), the code in FreeBSD doesn't check for bad sysctl
> values. My patch doesn't do it either for now. But wrong values could
> cause division by zero for example. Is there a way to check sysctls only
> when they are modified, instead of before every use?

Yes, use a SYSCTL_PROC() for those nodes.

> Last question: I expanded the Synaptics subtree with my own nodes but
> there are three nodes which are not used anymore. How should I handle
> deprecation of these nodes?

Just remove them.

=2D-=20
John Baldwin