How do I pass configuration parameters to a FreeBSD Device Driver ?

[M. Warner Losh]

In message: <200906040822.41153.marc.loerner at hob.de>
            Marc Loerner <marc.loerner at hob.de> writes:
: Am Donnerstag 04 Juni 2009 04:27:25 schrieb David Somayajulu:
: > Larry Maloney wrote:
: > > David Somayajulu wrote:
: > > > Hi All,
: > > > I would appreciate if you could let me know, how I can pass
: > >
: > > configuration parameters to a device driver, which can be processed
: > > during either probe() or attach() ? Is there a way to read them from a
: > > conf file of some sort ? Basically, I am interested in setting some
: > > tunable parameters during driver initialization, without needing to
: > > recompile the driver every time.
: > >
: > > > thanks
: > > > david Somayajulu
: > > >
: > > > _______________________________________________
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: > >
: > > Isn't that what the hints file is for?
: >
: > Sorry, I am sort of new to FreeBSD. From what I understand
: > /boot/device.hints gets read during boot time, the values cannot be changed
: > by the user while the kernel is running - am I correct ?
: >
: > I have a loadable driver module and would like to do the following:
: > 1. Set some tunable parameters of the driver.
: > 2. Load the driver. Run a few tests.
: > 3. Unload the driver.
: > 4. repeat steps 1 thru 3.
: >
: 
: I think exactly what you search is sysctls. There you have tunables to change 
: at runtime

It depends a lot on how the sysctl/tunable is used/set.  If you are
using pure hints, then you need to use the kenv method I talked
about.  If you are using a more general tunable (eg
hw.DRIVERNAME.rx_buffers, say), then that can be set at runtime, and
there's hooks into the driver that allow it to react to the new
value.  This can be a better choice than hints, but is a little harder
to code up.  But the different isn't that huge...

Warner