[PATCH] ALSA: core: Use the allocated major number with major=0

[PATCH] ALSA: core: Use the allocated major number with major=0

[Ali Ahmet Memiş]

Since commit bd8f21876189 ("ALSA: core: propagate actual error code from
register_chrdev"), alsa_sound_init() only treats negative values from
register_chrdev() as errors. With the major=0 module option
register_chrdev() allocates a major number dynamically and returns it
but snd_major and the devices still use 0. The devices are then
created without device numbers so no /dev/snd nodes appear and sound
is unusable.

Use the returned major number when major=0 is given.

Fixes: bd8f21876189 ("ALSA: core: propagate actual error code from register_chrdev")
Signed-off-by: Ali Ahmet Memiş <aliamemis@disroot.org>
---
 sound/core/sound.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/core/sound.c b/sound/core/sound.c
index 24f40763a20c..a0349a7e9495 100644
--- a/sound/core/sound.c
+++ b/sound/core/sound.c
@@ -396,7 +396,6 @@ static int __init alsa_sound_init(void)
 {
 	int err;
 
-	snd_major = major;
 	snd_ecards_limit = cards_limit;
 
 	err = register_chrdev(major, "alsa", &snd_fops);
@@ -404,6 +403,9 @@ static int __init alsa_sound_init(void)
 		pr_err("ALSA core: unable to register native major device number %d\n", major);
 		return err;
 	}
+	if (!major)
+		major = err;
+	snd_major = major;
 
 	err = snd_info_init();
 	if (err < 0) {
-- 
2.55.0

Re: [PATCH] ALSA: core: Use the allocated major number with major=0

[Bui Duc Phuc]

Hi Ali , Takashi-san,

>
> Since commit bd8f21876189 ("ALSA: core: propagate actual error code from
> register_chrdev"), alsa_sound_init() only treats negative values from
> register_chrdev() as errors. With the major=0 module option
> register_chrdev() allocates a major number dynamically and returns it
> but snd_major and the devices still use 0. The devices are then
> created without device numbers so no /dev/snd nodes appear and sound
> is unusable.


Note that major=0 has never worked, even before bd8f21876189: the old
code treated the positive return value of register_chrdev() as an
error and failed with -EIO. bd8f21876189 only changed the symptom.

So this patch adds support for a dynamic major rather than fixing a
regression. Takashi-san, is a dynamic major something ALSA wants to
support? If not, rejecting major=0 with -EINVAL might be simpler.

If it is kept, the Fixes tag is fine since the patch depends on
bd8f21876189, but please mention in the changelog that major=0
never worked before.

Best regards,
Phuc

Re: [PATCH] ALSA: core: Use the allocated major number with major=0

[Takashi Iwai]

On Mon, 12 Oct 2026 06:32:47 +0200,
Bui Duc Phuc wrote:
> 
> Hi Ali , Takashi-san,
> 
> >
> > Since commit bd8f21876189 ("ALSA: core: propagate actual error code from
> > register_chrdev"), alsa_sound_init() only treats negative values from
> > register_chrdev() as errors. With the major=0 module option
> > register_chrdev() allocates a major number dynamically and returns it
> > but snd_major and the devices still use 0. The devices are then
> > created without device numbers so no /dev/snd nodes appear and sound
> > is unusable.
> 
> 
> Note that major=0 has never worked, even before bd8f21876189: the old
> code treated the positive return value of register_chrdev() as an
> error and failed with -EIO. bd8f21876189 only changed the symptom.
> 
> So this patch adds support for a dynamic major rather than fixing a
> regression. Takashi-san, is a dynamic major something ALSA wants to
> support?

No, it's supposed to be only the fixed one.

If there is a real demand, we can extend the implementation, but I
don't know of such a request.


Takashi

>  If not, rejecting major=0 with -EINVAL might be simpler.
> If it is kept, the Fixes tag is fine since the patch depends on
> bd8f21876189, but please mention in the changelog that major=0
> never worked before.
> 
> Best regards,
> Phuc

Re: [PATCH] ALSA: core: Use the allocated major number with major=0

[Bui Duc Phuc]

Hi Takashi-san,

> > Note that major=0 has never worked, even before bd8f21876189: the old
> > code treated the positive return value of register_chrdev() as an
> > error and failed with -EIO. bd8f21876189 only changed the symptom.
> >
> > So this patch adds support for a dynamic major rather than fixing a
> > regression. Takashi-san, is a dynamic major something ALSA wants to
> > support?
>
> No, it's supposed to be only the fixed one.
>
> If there is a real demand, we can extend the implementation, but I
> don't know of such a request.
>

Thank you for the clarification.

Best regards,
Phuc