[alsa-devel] udev rules prefix

[Ivailo Monev]

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?