[alsa-devel] udev rules prefix

[Takashi Iwai]

At Fri, 15 Nov 2013 13:16:41 +0000,
Ivailo Monev wrote:
> 
> On 11/14/13 16:14, Takashi Iwai wrote:
> > At Thu, 14 Nov 2013 18:49:02 +0000,
> > Ivailo Monev wrote:
> >> On 11/14/13 10:51, Takashi Iwai wrote:
> >>> At Thu, 14 Nov 2013 13:24:49 +0000,
> >>> Ivailo Monev wrote:
> >>>> On 11/14/13 09:42, Takashi Iwai wrote:
> >>>>> At Thu, 14 Nov 2013 12:08:47 +0000,
> >>>>> Ivailo Monev wrote:
> >>>>>> On 11/14/13 02:48, David Henningsson wrote:
> >>>>>>> On 11/13/2013 09:36 PM, Ivailo wrote:
> >>>>>>>> Hello,
> >>>>>>>>
> >>>>>>>> the default prefix for alsa-utils is /usr however the udev rules directory
> >>>>>>>> is /lib/udev/rules.d thus on setups with separate partition for /usr the
> >>>>>>>> binaries, from /usr/bin and /usr/sbin, will likely not be available during
> >>>>>>>> the boot process and the udev rule will fail to restore the state.
> >>>>>>>>
> >>>>>>>> I suggest that the udev rules directory follows the prefix or append /usr
> >>>>>>>> to it to resolve this.
> >>>>>>>>
> >>>>>>>> Cheers!
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> ALSA merely follows what udev dictates, so I think your
> >>>>>>> question/suggestion is better redirected on the udev (now systemd)
> >>>>>>> mailinglist. Or potentially that of your distro.
> >>>>>>>
> >>>>>> Actually, you are not following what udev dictates (unless I'm missing
> >>>>>> something).
> >>>>>> By default, systemd (and more importantly udev) will be installed with
> >>>>>> /usr prefix
> >>>>>> (which is wrong in it self because it blindly assumes that /usr has been
> >>>>>> mounted
> >>>>>> via initrd/initramfs where separate /usr partition is in use but let's
> >>>>>> not talk about
> >>>>>> this here).
> >>>>>>
> >>>>>>
> >>>>>> On 11/14/13 06:45, Takashi Iwai wrote:
> >>>>>>> At Wed, 13 Nov 2013 20:36:48 +0000,
> >>>>>>> Ivailo wrote:
> >>>>>>>> Hello,
> >>>>>>>>
> >>>>>>>> the default prefix for alsa-utils is /usr however the udev rules directory
> >>>>>>>> is /lib/udev/rules.d thus on setups with separate partition for /usr the
> >>>>>>>> binaries, from /usr/bin and /usr/sbin, will likely not be available during
> >>>>>>>> the boot process and the udev rule will fail to restore the state.
> >>>>>>> Not true.  /lib must be always present at boot even if /usr isn't
> >>>>>>> mounted.  That's the reason why /lib/udev was chosen as default in the
> >>>>>>> past.
> >>>>>>>
> >>>>>>>
> >>>>>>> Takashi
> >>>>>> You got me wrong, I know that /lib should be available on early boot
> >>>>>> (unless it's a
> >>>>>> symlink, like in Arch Linux) but the point is that since the alsa-utils
> >>>>>> binaries are
> >>>>>> installed in /usr so should be the udev rules otherwise during boot
> >>>>>> without /usr
> >>>>>> being mounted you will see error message about /usr/sbin/alsactl.
> >>>>> Theoretically yes, but this has been rather less problems than
> >>>>> creating a non-existing /usr/lib/udev in the past.  That's the very
> >>>>> reason of hard-coded /lib/udev.  Changing the default behavior is
> >>>>> often worse unless you really do it carefully with consideration of
> >>>>> compatibility with old systems.
> >>>>>
> >>>>> So, if you want to change the default, don't hard code again.  Make
> >>>>> configure to guess the right place.  A patch achieving it is welcome.
> >>>>>
> >>>>>
> >>>>> Takashi
> >>>> Ok, here is the patch:
> >>>>
> >>>>    From 74faeceb26c4730d6150e726792f6eb1f257b03e Mon Sep 17 00:00:00 2001
> >>>> From: Ivailo Monev <xakepa10 at gmail.com>
> >>>> Date: Thu, 14 Nov 2013 13:13:43 +0000
> >>>> Subject: [PATCH 1/1] detect udevdir via pkg-config
> >>>>
> >>>> ---
> >>>>     configure.in | 2 +-
> >>>>     1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/configure.in b/configure.in
> >>>> index 3ae3209..74b891e 100644
> >>>> --- a/configure.in
> >>>> +++ b/configure.in
> >>>> @@ -121,7 +121,7 @@ AM_CONDITIONAL(USE_XMLTO, test x"$xmlto" = xyes)
> >>>>     AC_ARG_WITH(
> >>>>             [udev-rules-dir],
> >>>>             AS_HELP_STRING([--with-udev-rules-dir],[Directory where to
> >>>> install udev rules to (defaults to /lib/udev/rules.d)]),
> >>>> -        [udevrulesdir=$withval], [udevrulesdir="/lib/udev/rules.d"])
> >>>> +        [udevrulesdir=$withval], [udevrulesdir=$($PKG_CONFIG udev
> >>>> --variable=udevdir)"/rules.d"])
> >>>>     AC_SUBST(udevrulesdir)
> >>> This pkg-config option isn't always available.  Make sure to have a
> >>> proper fallback to /lib/udev/rules.d.  Also, update the help text,
> >>> too.
> >>>
> >>>
> >>> thanks,
> >>>
> >>> Takashi
> >> I'm not an autotools guru but there is PKG_PROG_PKG_CONFIG in
> >> configure.in which is supposed to ensure that pkg-config is installed,
> >> right? Besides, with_systemdsystemunitdir uses almost the same
> >> method as in my patch which I looked at before submitting it.
> > udev.pc is no hard requirement for alsa-utils, thus there is no
> > guarantee that "pkg-config udev" works as you expected.  If it's not
> > installed, pkg-config doesn't complain but just gives an empty
> > string.
> >
> >
> >> Anyway, here is an updated patch that keeps things more like the
> >> other tests in configure.in:
> >>
> >>   From b30824ef1682f3040d53c1495dae308f51a4f380 Mon Sep 17 00:00:00 2001
> >> From: Ivailo Monev <xakepa10 at gmail.com>
> >> Date: Thu, 14 Nov 2013 18:41:55 +0000
> >> Subject: [PATCH 1/1] detect udevdir via pkg-config
> >>
> >> ---
> >>    configure.in | 4 ++--
> >>    1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/configure.in b/configure.in
> >> index 3ae3209..e8e1e82 100644
> >> --- a/configure.in
> >> +++ b/configure.in
> >> @@ -120,8 +120,8 @@ AM_CONDITIONAL(USE_XMLTO, test x"$xmlto" = xyes)
> >>
> >>    AC_ARG_WITH(
> >>            [udev-rules-dir],
> >> -        AS_HELP_STRING([--with-udev-rules-dir],[Directory where to
> >> install udev rules to (defaults to /lib/udev/rules.d)]),
> >> -        [udevrulesdir=$withval], [udevrulesdir="/lib/udev/rules.d"])
> >> +        AS_HELP_STRING([--with-udev-rules-dir=DIR],[Directory where to
> >> install udev rules to (default=auto)]),
> >> +        [udevrulesdir="$withval"], [udevrulesdir=$($PKG_CONFIG udev
> >> --variable=udevdir)/rules.d])
> >>    AC_SUBST(udevrulesdir)
> >>
> >>    dnl Checks for header files.
> >> -- 
> >> 1.8.3.4
> >>
> >> If you are not happy with my patch you can write your own based
> >> which uses the pkg-config approach without hesitation, I will not
> >> get upset.
> >>
> >> And still, will you do something about separate /usr or not? Just
> >> asking. As stated before, this patch will not solve it but replace
> >> the path hard coding with a flexible method.
> > It's matter distributors decide.  The default value is just some
> > value that might work.  Users and distros must read the document and
> > give the proper configure options.
> >
> >
> > Takashi
> Sorry for the late reply.
> 
> So, I get that there is a variation from distribution to distribution.
> But what if udevrulesdir respects the default prefix
> (AC_PREFIX_DEFAULT)? That way, the issue in my first email will
> be solved. Will a patch for it be accepted?

It'd break the previously working behavior.

Simply fallback to the old value (/lib/udev/) when pkg-config gives an
empty string.  That should suffice for both cases.


Takashi