A few more cleanups and improvements that have been overlooked:

- Use ARRAY_SIZE() macro appropriately
- Code shuffling for minor optimization
- Omit superfluous variable initializations
- Get rid of superfluous NULL checks
- Add const to snd_us16x08_control_params definitions

No functional changes.
Reviewed-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

There are a few places leaking memory and doing double-free in
mixer_us16x08.c.

The driver allocates a usb_mixer_elem_info object at each
add_new_ctl() call.  This has to be freed via kctl->private_free, but
currently this is done properly only for some controls.

Also, the driver allocates three external objects (comp_store,
eq_store, meter_store), and these are referred in elem->private_data
(it's not kctl->private_data).  And these have to be released, but
there are none doing it.  Moreover, these extra objects have to be
released only once.  Thus the release should be done only by the first
kctl element that refers to it.

For fixing these, we call either snd_usb_mixer_elem_free() (only for
kctl->private_data) or elem_private_free() (for both
kctl->private_data and elem->private_data) via kctl->private_free
appropriately.

Last but not least, snd_us16x08_controls_create() may return in the
middle without releasing the allocated *_store objects due to an
error.  For fixing this, we shuffle the allocation code so that it's
called just before its reference.

Fixes: d2bb390a ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Reported-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Reviewed-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

Variable length array is used in 'snd_us16x08_meter_get()', while there
is no need. It's better to purge it because variable length array has
overhead for stack handling.

This commit replaces the array with static length. Sparse generated below
warning.

sound/usb/mixer_us16x08.c:714:18: warning: Variable length array is used.

Fixes: d2bb390a ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Signed-off-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

When accessed inner a file, functions should have static qualifier for
local-linkage.

This commit fixes the bug. Sparse generated below warning.

sound/usb/mixer_us16x08.c:1043:32: warning: symbol 'snd_us16x08_create_meter_store' was not declared. Should it be static?

Fixes: d2bb390a ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Signed-off-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

When accessed by one referrer inner a file, variables should have static
qualifier to declare local-linkage.

This commit fixes the bug. Sparse generated below warnings.
sound/usb/mixer_us16x08.c:156:13: warning: duplicate const
sound/usb/mixer_us16x08.c:156:18: warning: symbol 'route_names' was not declared. Should it be static?

Fixes: d2bb390a ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Signed-off-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

Add mixer quirk for Tascam US-16x08 usb interface.
Even that this is an usb compliant device,
the input channels and DSP functions (EQ/Compressor) aren't accessible
by default.
Signed-off-by: NDetlef Urban <onkel@paraair.de>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>