From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?utf-8?Q?Ludovic_Court=C3=A8s?= <ludo@gnu.org>
Subject: Re: 01/02: services: Allow modprobe to use "/etc/modprobe.d".
Date: Tue, 07 Apr 2020 11:35:45 +0200
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In-Reply-To: <00d7800adbfc1fa955ed503c1ba38e00@waegenei.re> (Brice
 Waegeneire's message of "Mon, 06 Apr 2020 07:54:47 +0000")
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To: Brice Waegeneire <brice@waegenei.re>
Cc: guix-devel@gnu.org

Hi,

Brice Waegeneire <brice@waegenei.re> skribis:

> On 2020-04-05 21:15, Ludovic Court=C3=A8s wrote:
>> guix-commits@gnu.org skribis:
>>>                    #~(begin
>>>                        (setenv "LINUX_MODULE_DIRECTORY"
>>>                                "/run/booted-system/kernel/lib/modules")
>>> +                      ;; FIXME: Remove this crutch when the patch
>>> #40422,
>>> +                      ;; updating to kmod 27 is merged.
>>> +                      (setenv "MODPROBE_OPTIONS"
>>> +                              "-C /etc/modprobe.d")
>>
>> [...]
>>
>>> +  (services (cons* (service kernel-module-loader-service-type
>>> +                            '("ddcci" "ddcci_backlight"))
>>> +                   (simple-service 'ddcci-config etc-service-type
>>> +                                   (list `("modprobe.d/ddcci.conf"
>>> +                                           ,ddcci-config)))
>>> +                   %base-services))
>>
>> Looking at this, I was wondering if it would be possible to not use
>> /etc/modprobe.d and instead have a way to tell the modprobe wrapper to
>> pass =E2=80=9C-C /gnu/store/=E2=80=A6-modprobe.d=E2=80=9D, which would c=
ontain the right thing.
>>
>> Thoughts?
>
> What's the issue with using /etc/modrpobe.d?

In general, use of the global file system name space isn=E2=80=99t great: i=
t=E2=80=99s
ambiguous (compare to a /gnu/store reference) and doesn=E2=80=99t work well=
 upon
rollback or reconfigure (things that refer to /etc end up referring to
the =E2=80=9Cnew=E2=80=9D /etc after reconfigure, even though that might no=
t actually
work.)

Conversely, =E2=80=9C-C /gnu/store/=E2=80=A6-modprobe.d=E2=80=9D unambiguou=
sly refers to the
intended directory.

WDYT?

> As noted in the comments I thought setting MODPROBE_OPTIONS was kinda
> of a
> hack; #40422[0] was there to fix it. But if you think it's appropriate
> to
> use this environment variable it can be done in a future
> =E2=80=9Ckernel-module-configuration-service-type=E2=80=9D we discussed w=
ith Danny[1].

Sure, no problem!

> Instead of extending =E2=80=9Cetc-service-type=E2=80=9D we would use
> =E2=80=9Cactivation-service-type=E2=80=9D, as =E2=80=9C%modprobe-wrapper=
=E2=80=9D is currently put
> in place by a simple activation service.

Makes sense.

Thank you,
Ludo=E2=80=99.