svn commit: r328257 - in head/sys: arm/broadcom/bcm2835 dts/arm modules

[Emmanuel Vadot]

On Mon, 22 Jan 2018 14:07:30 +0000
"Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:

> --------
> In message <20180122145117.08173be547f5dd6fef296732 at bidouilliste.com>, Emmanuel
>  Vadot writes:
> 
> > Using the same logic as before one could have a script starting some
> >pwm stuff (or simply using /etc/sysctl.conf)
> > Also this is not how DT is suppose to work, if the status ==
> >'disabled' no driver should attach.
> 
> That doesn't make *any* UX sense.
> 
> "disabled" indicates that it can be enabled, and there is absolutely
> no reason to force users to reboot, when all that stands between
> them and using their hardware is a random setting in a file.

 To be more clear, disabled mean that the node should not be used.
 In a industrial board you will always have every usable node enabled,
in the SBC world where you have a way to plug daughter card and
exchange them or even use the exposed pins directly there is no way to
know what the user will do so every node not used by the SBC must be
disabled.
 This is the overlay part of DT that is responsible to enable them

> Explicitly kldload'ing a device-driver is as clear a "Enable it, please"
> instruction as you can get from the user.

 But device driver != DT node

> If you want to lock down this DT-device because some other
> device/pin-mux/whatever makes its use impossible, then
> status should not be "disabled" but "locked" or "impossible".

 Feel free to talk to the DT guys.

> In particular it is *horrible* UX, that you kldload a device-driver
> for hardware you know is there, and it just silently doesn't do
> anything.  At the very least it should give a diagnostic.
> 
> Maybe something like:
> 
> 	"For no good reason this device is disabled, google for
> 	an hour, try to come up with a device tree overlay, reboot
> 	to install it and see if you get lucky."
> 
> :-)
> 
> >> > Can you please revert this part ?
> >> 
> >> Once I find out how to get similar behaviour, ie: kldload without
> >> having to reboot to load a DT-overlay.
> >
> > Nobody is working on that right now (that I know of).
> 
> Let me know when it works, and I'll remove my hack then.
> 
> In the meantime, don't load bcm283x_pwm if you don't plan on
> using the PWM on GPIO12 on your RPI[23].
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.


-- 
Emmanuel Vadot <manu at bidouilliste.com> <manu at freebsd.org>