ALSA: usb-audio: use kzalloc_flex

[PATCH] ALSA: usb-audio: use kzalloc_flex

Posted by Rosen Penev 3 weeks, 5 days ago

Saves one allocation by using a flexible array member.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 sound/usb/mixer.c | 22 +++++++---------------
 sound/usb/mixer.h |  5 +++--
 2 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 7007e0c9489b..337815b9e72c 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1393,7 +1393,7 @@ static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol,
 		if (!cval->initialized) {
 			get_min_max_with_quirks(cval, 0, kcontrol);
 			if (cval->initialized && cval->dBmin >= cval->dBmax) {
-				kcontrol->vd[0].access &= 
+				kcontrol->vd[0].access &=
 					~(SNDRV_CTL_ELEM_ACCESS_TLV_READ |
 					  SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
 				snd_ctl_notify(cval->head.mixer->chip->card,
@@ -3006,15 +3006,12 @@ static void snd_usb_mixer_free(struct usb_mixer_interface *mixer)
 	snd_usb_mixer_disconnect(mixer);
 
 	/* Unregister controls first, snd_ctl_remove() frees the element */
-	if (mixer->id_elems) {
-		for (id = 0; id < MAX_ID_ELEMS; id++) {
-			for (list = mixer->id_elems[id]; list; list = next) {
-				next = list->next_id_elem;
-				if (list->kctl)
-					snd_ctl_remove(mixer->chip->card, list->kctl);
-			}
+	for (id = 0; id < MAX_ID_ELEMS; id++) {
+		for (list = mixer->id_elems[id]; list; list = next) {
+			next = list->next_id_elem;
+			if (list->kctl)
+				snd_ctl_remove(mixer->chip->card, list->kctl);
 		}
-		kfree(mixer->id_elems);
 	}
 	if (mixer->urb) {
 		kfree(mixer->urb->transfer_buffer);
@@ -3652,16 +3649,11 @@ int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif)
 
 	strscpy(chip->card->mixername, "USB Mixer");
 
-	mixer = kzalloc_obj(*mixer);
+	mixer = kzalloc_flex(*mixer, id_elems, MAX_ID_ELEMS);
 	if (!mixer)
 		return -ENOMEM;
 	mixer->chip = chip;
 	mixer->ignore_ctl_error = !!(chip->quirk_flags & QUIRK_FLAG_IGNORE_CTL_ERROR);
-	mixer->id_elems = kzalloc_objs(*mixer->id_elems, MAX_ID_ELEMS);
-	if (!mixer->id_elems) {
-		kfree(mixer);
-		return -ENOMEM;
-	}
 
 	mixer->hostif = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];
 	switch (get_iface_desc(mixer->hostif)->bInterfaceProtocol) {
diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
index 167fbfcf01ac..30dd30b925fc 100644
--- a/sound/usb/mixer.h
+++ b/sound/usb/mixer.h
@@ -19,8 +19,6 @@ struct usb_mixer_interface {
 	struct list_head list;
 	unsigned int ignore_ctl_error;
 	struct urb *urb;
-	/* array[MAX_ID_ELEMS], indexed by unit id */
-	struct usb_mixer_elem_list **id_elems;
 
 	/* the usb audio specification version this interface complies to */
 	int protocol;
@@ -42,6 +40,9 @@ struct usb_mixer_interface {
 	void *private_data;
 	void (*private_free)(struct usb_mixer_interface *mixer);
 	void (*private_suspend)(struct usb_mixer_interface *mixer);
+
+	/* array[MAX_ID_ELEMS], indexed by unit id */
+	struct usb_mixer_elem_list *id_elems[];
 };
 
 #define MAX_CHANNELS	16	/* max logical channels */
-- 
2.53.0

Re: [PATCH] ALSA: usb-audio: use kzalloc_flex

Posted by Takashi Iwai 3 weeks, 5 days ago

On Thu, 12 Mar 2026 00:27:48 +0100,
Rosen Penev wrote:
> 
> Saves one allocation by using a flexible array member.

As it's a fixed size array, it doesn't have to be a flex array at all,
so it can be even simpler.


thanks,

Takashi

> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  sound/usb/mixer.c | 22 +++++++---------------
>  sound/usb/mixer.h |  5 +++--
>  2 files changed, 10 insertions(+), 17 deletions(-)
> 
> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> index 7007e0c9489b..337815b9e72c 100644
> --- a/sound/usb/mixer.c
> +++ b/sound/usb/mixer.c
> @@ -1393,7 +1393,7 @@ static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol,
>  		if (!cval->initialized) {
>  			get_min_max_with_quirks(cval, 0, kcontrol);
>  			if (cval->initialized && cval->dBmin >= cval->dBmax) {
> -				kcontrol->vd[0].access &= 
> +				kcontrol->vd[0].access &=
>  					~(SNDRV_CTL_ELEM_ACCESS_TLV_READ |
>  					  SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
>  				snd_ctl_notify(cval->head.mixer->chip->card,
> @@ -3006,15 +3006,12 @@ static void snd_usb_mixer_free(struct usb_mixer_interface *mixer)
>  	snd_usb_mixer_disconnect(mixer);
>  
>  	/* Unregister controls first, snd_ctl_remove() frees the element */
> -	if (mixer->id_elems) {
> -		for (id = 0; id < MAX_ID_ELEMS; id++) {
> -			for (list = mixer->id_elems[id]; list; list = next) {
> -				next = list->next_id_elem;
> -				if (list->kctl)
> -					snd_ctl_remove(mixer->chip->card, list->kctl);
> -			}
> +	for (id = 0; id < MAX_ID_ELEMS; id++) {
> +		for (list = mixer->id_elems[id]; list; list = next) {
> +			next = list->next_id_elem;
> +			if (list->kctl)
> +				snd_ctl_remove(mixer->chip->card, list->kctl);
>  		}
> -		kfree(mixer->id_elems);
>  	}
>  	if (mixer->urb) {
>  		kfree(mixer->urb->transfer_buffer);
> @@ -3652,16 +3649,11 @@ int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif)
>  
>  	strscpy(chip->card->mixername, "USB Mixer");
>  
> -	mixer = kzalloc_obj(*mixer);
> +	mixer = kzalloc_flex(*mixer, id_elems, MAX_ID_ELEMS);
>  	if (!mixer)
>  		return -ENOMEM;
>  	mixer->chip = chip;
>  	mixer->ignore_ctl_error = !!(chip->quirk_flags & QUIRK_FLAG_IGNORE_CTL_ERROR);
> -	mixer->id_elems = kzalloc_objs(*mixer->id_elems, MAX_ID_ELEMS);
> -	if (!mixer->id_elems) {
> -		kfree(mixer);
> -		return -ENOMEM;
> -	}
>  
>  	mixer->hostif = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];
>  	switch (get_iface_desc(mixer->hostif)->bInterfaceProtocol) {
> diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
> index 167fbfcf01ac..30dd30b925fc 100644
> --- a/sound/usb/mixer.h
> +++ b/sound/usb/mixer.h
> @@ -19,8 +19,6 @@ struct usb_mixer_interface {
>  	struct list_head list;
>  	unsigned int ignore_ctl_error;
>  	struct urb *urb;
> -	/* array[MAX_ID_ELEMS], indexed by unit id */
> -	struct usb_mixer_elem_list **id_elems;
>  
>  	/* the usb audio specification version this interface complies to */
>  	int protocol;
> @@ -42,6 +40,9 @@ struct usb_mixer_interface {
>  	void *private_data;
>  	void (*private_free)(struct usb_mixer_interface *mixer);
>  	void (*private_suspend)(struct usb_mixer_interface *mixer);
> +
> +	/* array[MAX_ID_ELEMS], indexed by unit id */
> +	struct usb_mixer_elem_list *id_elems[];
>  };
>  
>  #define MAX_CHANNELS	16	/* max logical channels */
> -- 
> 2.53.0
>

Re: [PATCH] ALSA: usb-audio: use kzalloc_flex

Posted by Rosen Penev 3 weeks, 5 days ago

On Wed, Mar 11, 2026 at 11:34 PM Takashi Iwai <tiwai@suse.de> wrote:
>
> On Thu, 12 Mar 2026 00:27:48 +0100,
> Rosen Penev wrote:
> >
> > Saves one allocation by using a flexible array member.
>
> As it's a fixed size array, it doesn't have to be a flex array at all,
> so it can be even simpler.
That's true. The comment even admits as such. Wonder why it was ever a
pointer allocated with calloc...
>
>
> thanks,
>
> Takashi
>
> >
> > Signed-off-by: Rosen Penev <rosenp@gmail.com>
> > ---
> >  sound/usb/mixer.c | 22 +++++++---------------
> >  sound/usb/mixer.h |  5 +++--
> >  2 files changed, 10 insertions(+), 17 deletions(-)
> >
> > diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> > index 7007e0c9489b..337815b9e72c 100644
> > --- a/sound/usb/mixer.c
> > +++ b/sound/usb/mixer.c
> > @@ -1393,7 +1393,7 @@ static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol,
> >               if (!cval->initialized) {
> >                       get_min_max_with_quirks(cval, 0, kcontrol);
> >                       if (cval->initialized && cval->dBmin >= cval->dBmax) {
> > -                             kcontrol->vd[0].access &=
> > +                             kcontrol->vd[0].access &=
> >                                       ~(SNDRV_CTL_ELEM_ACCESS_TLV_READ |
> >                                         SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
> >                               snd_ctl_notify(cval->head.mixer->chip->card,
> > @@ -3006,15 +3006,12 @@ static void snd_usb_mixer_free(struct usb_mixer_interface *mixer)
> >       snd_usb_mixer_disconnect(mixer);
> >
> >       /* Unregister controls first, snd_ctl_remove() frees the element */
> > -     if (mixer->id_elems) {
> > -             for (id = 0; id < MAX_ID_ELEMS; id++) {
> > -                     for (list = mixer->id_elems[id]; list; list = next) {
> > -                             next = list->next_id_elem;
> > -                             if (list->kctl)
> > -                                     snd_ctl_remove(mixer->chip->card, list->kctl);
> > -                     }
> > +     for (id = 0; id < MAX_ID_ELEMS; id++) {
> > +             for (list = mixer->id_elems[id]; list; list = next) {
> > +                     next = list->next_id_elem;
> > +                     if (list->kctl)
> > +                             snd_ctl_remove(mixer->chip->card, list->kctl);
> >               }
> > -             kfree(mixer->id_elems);
> >       }
> >       if (mixer->urb) {
> >               kfree(mixer->urb->transfer_buffer);
> > @@ -3652,16 +3649,11 @@ int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif)
> >
> >       strscpy(chip->card->mixername, "USB Mixer");
> >
> > -     mixer = kzalloc_obj(*mixer);
> > +     mixer = kzalloc_flex(*mixer, id_elems, MAX_ID_ELEMS);
> >       if (!mixer)
> >               return -ENOMEM;
> >       mixer->chip = chip;
> >       mixer->ignore_ctl_error = !!(chip->quirk_flags & QUIRK_FLAG_IGNORE_CTL_ERROR);
> > -     mixer->id_elems = kzalloc_objs(*mixer->id_elems, MAX_ID_ELEMS);
> > -     if (!mixer->id_elems) {
> > -             kfree(mixer);
> > -             return -ENOMEM;
> > -     }
> >
> >       mixer->hostif = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];
> >       switch (get_iface_desc(mixer->hostif)->bInterfaceProtocol) {
> > diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
> > index 167fbfcf01ac..30dd30b925fc 100644
> > --- a/sound/usb/mixer.h
> > +++ b/sound/usb/mixer.h
> > @@ -19,8 +19,6 @@ struct usb_mixer_interface {
> >       struct list_head list;
> >       unsigned int ignore_ctl_error;
> >       struct urb *urb;
> > -     /* array[MAX_ID_ELEMS], indexed by unit id */
> > -     struct usb_mixer_elem_list **id_elems;
> >
> >       /* the usb audio specification version this interface complies to */
> >       int protocol;
> > @@ -42,6 +40,9 @@ struct usb_mixer_interface {
> >       void *private_data;
> >       void (*private_free)(struct usb_mixer_interface *mixer);
> >       void (*private_suspend)(struct usb_mixer_interface *mixer);
> > +
> > +     /* array[MAX_ID_ELEMS], indexed by unit id */
> > +     struct usb_mixer_elem_list *id_elems[];
> >  };
> >
> >  #define MAX_CHANNELS 16      /* max logical channels */
> > --
> > 2.53.0
> >

Re: [PATCH] ALSA: usb-audio: use kzalloc_flex

Posted by Rosen Penev 3 weeks, 3 days ago

On Wed, Mar 11, 2026 at 11:45 PM Rosen Penev <rosenp@gmail.com> wrote:
>
> On Wed, Mar 11, 2026 at 11:34 PM Takashi Iwai <tiwai@suse.de> wrote:
> >
> > On Thu, 12 Mar 2026 00:27:48 +0100,
> > Rosen Penev wrote:
> > >
> > > Saves one allocation by using a flexible array member.
> >
> > As it's a fixed size array, it doesn't have to be a flex array at all,
> > so it can be even simpler.
> That's true. The comment even admits as such. Wonder why it was ever a
> pointer allocated with calloc...
Oh no I see the issue:

sound/usb/mixer.c:#define MAX_ID_ELEMS  256

I don't think this is supposed to be in the header.
> >
> >
> > thanks,
> >
> > Takashi
> >
> > >
> > > Signed-off-by: Rosen Penev <rosenp@gmail.com>
> > > ---
> > >  sound/usb/mixer.c | 22 +++++++---------------
> > >  sound/usb/mixer.h |  5 +++--
> > >  2 files changed, 10 insertions(+), 17 deletions(-)
> > >
> > > diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> > > index 7007e0c9489b..337815b9e72c 100644
> > > --- a/sound/usb/mixer.c
> > > +++ b/sound/usb/mixer.c
> > > @@ -1393,7 +1393,7 @@ static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol,
> > >               if (!cval->initialized) {
> > >                       get_min_max_with_quirks(cval, 0, kcontrol);
> > >                       if (cval->initialized && cval->dBmin >= cval->dBmax) {
> > > -                             kcontrol->vd[0].access &=
> > > +                             kcontrol->vd[0].access &=
> > >                                       ~(SNDRV_CTL_ELEM_ACCESS_TLV_READ |
> > >                                         SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
> > >                               snd_ctl_notify(cval->head.mixer->chip->card,
> > > @@ -3006,15 +3006,12 @@ static void snd_usb_mixer_free(struct usb_mixer_interface *mixer)
> > >       snd_usb_mixer_disconnect(mixer);
> > >
> > >       /* Unregister controls first, snd_ctl_remove() frees the element */
> > > -     if (mixer->id_elems) {
> > > -             for (id = 0; id < MAX_ID_ELEMS; id++) {
> > > -                     for (list = mixer->id_elems[id]; list; list = next) {
> > > -                             next = list->next_id_elem;
> > > -                             if (list->kctl)
> > > -                                     snd_ctl_remove(mixer->chip->card, list->kctl);
> > > -                     }
> > > +     for (id = 0; id < MAX_ID_ELEMS; id++) {
> > > +             for (list = mixer->id_elems[id]; list; list = next) {
> > > +                     next = list->next_id_elem;
> > > +                     if (list->kctl)
> > > +                             snd_ctl_remove(mixer->chip->card, list->kctl);
> > >               }
> > > -             kfree(mixer->id_elems);
> > >       }
> > >       if (mixer->urb) {
> > >               kfree(mixer->urb->transfer_buffer);
> > > @@ -3652,16 +3649,11 @@ int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif)
> > >
> > >       strscpy(chip->card->mixername, "USB Mixer");
> > >
> > > -     mixer = kzalloc_obj(*mixer);
> > > +     mixer = kzalloc_flex(*mixer, id_elems, MAX_ID_ELEMS);
> > >       if (!mixer)
> > >               return -ENOMEM;
> > >       mixer->chip = chip;
> > >       mixer->ignore_ctl_error = !!(chip->quirk_flags & QUIRK_FLAG_IGNORE_CTL_ERROR);
> > > -     mixer->id_elems = kzalloc_objs(*mixer->id_elems, MAX_ID_ELEMS);
> > > -     if (!mixer->id_elems) {
> > > -             kfree(mixer);
> > > -             return -ENOMEM;
> > > -     }
> > >
> > >       mixer->hostif = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];
> > >       switch (get_iface_desc(mixer->hostif)->bInterfaceProtocol) {
> > > diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
> > > index 167fbfcf01ac..30dd30b925fc 100644
> > > --- a/sound/usb/mixer.h
> > > +++ b/sound/usb/mixer.h
> > > @@ -19,8 +19,6 @@ struct usb_mixer_interface {
> > >       struct list_head list;
> > >       unsigned int ignore_ctl_error;
> > >       struct urb *urb;
> > > -     /* array[MAX_ID_ELEMS], indexed by unit id */
> > > -     struct usb_mixer_elem_list **id_elems;
> > >
> > >       /* the usb audio specification version this interface complies to */
> > >       int protocol;
> > > @@ -42,6 +40,9 @@ struct usb_mixer_interface {
> > >       void *private_data;
> > >       void (*private_free)(struct usb_mixer_interface *mixer);
> > >       void (*private_suspend)(struct usb_mixer_interface *mixer);
> > > +
> > > +     /* array[MAX_ID_ELEMS], indexed by unit id */
> > > +     struct usb_mixer_elem_list *id_elems[];
> > >  };
> > >
> > >  #define MAX_CHANNELS 16      /* max logical channels */
> > > --
> > > 2.53.0
> > >

Re: [PATCH] ALSA: usb-audio: use kzalloc_flex

Posted by Takashi Iwai 3 weeks, 3 days ago

On Fri, 13 Mar 2026 23:02:08 +0100,
Rosen Penev wrote:
> 
> On Wed, Mar 11, 2026 at 11:45 PM Rosen Penev <rosenp@gmail.com> wrote:
> >
> > On Wed, Mar 11, 2026 at 11:34 PM Takashi Iwai <tiwai@suse.de> wrote:
> > >
> > > On Thu, 12 Mar 2026 00:27:48 +0100,
> > > Rosen Penev wrote:
> > > >
> > > > Saves one allocation by using a flexible array member.
> > >
> > > As it's a fixed size array, it doesn't have to be a flex array at all,
> > > so it can be even simpler.
> > That's true. The comment even admits as such. Wonder why it was ever a
> > pointer allocated with calloc...
> Oh no I see the issue:
> 
> sound/usb/mixer.c:#define MAX_ID_ELEMS  256
> 
> I don't think this is supposed to be in the header.

Why?


Takashi