[Letux-kernel] how to get your ttyOx back

H. Nikolaus Schaller hns at goldelico.com
Fri Sep 21 07:44:01 CEST 2018


> Am 21.09.2018 um 07:23 schrieb Andreas Kemnade <andreas at kemnade.info>:
> 
> Hi,
> 
> On Wed, 19 Sep 2018 22:28:25 +0200
> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> 
>> Hi Andreas,
>> 
>>> Am 19.09.2018 um 18:40 schrieb Andreas Kemnade <andreas at kemnade.info>:
>>> 
>>> Hi,
>>> 
>>> I am just wondering how I can get back my ttyOx (especially the gps)
>>> when running kernels without our special gps driver. The reason is that
>>> I want to have a clear picture about power consumption, so having
>>> a userspace hack to disable gps if there is no kernel support for it
>>> would be helpful for example when you want to git bisect stuff.
>> 
>> It should suffice to add a blacklist entry for the w2sg (and w2cbw for bluetooth)
>> driver to /etc/modprobe.d/something.conf
>> 
> well, if there is no module, I cannot blacklist that.
> On a mainline kernel with letux-dtbs, I have only ttyO2 and O3.

ttyO2 is the console and ttyO3 is an UART internal to the OMAP3 with no external connection. Maybe for car-kit.

I thought that the code registering a tty for serdev does hide it,
so a module not loaded would not hide. But it seems as if serdev is
hiding it as soon as a child node appears in the DTS.

Maybe it suffices to set the child node to status = "disabled"?

If not we should file a bug...

> 
>> IMHO, in that case there is no serdev driver that hides the /dev/ttyOx.
>> 
>> In the worst case you can defconfigure the SERDEV subsystem.
>> 
> yes, that works.

Good to know.

BR,
Nikolaus

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