So far, we blindly assumed that the all usb-audio mixer elements
follow the standard and apply the standard resume method for the
registered elements in the id_elems[] list. However, some quirks
really need the own resume and it's incomplete for now.
This patch enhances the resume handling in two folds:
- split some fields in struct usb_mixer_elem_info into a smaller
header struct (usb_mixer_elem_list) for keeping the minimal
information in the linked-list; the usb_mixer_elem_info embeds this
header struct instead
- add resume and dump callbacks to usb_mixer_elem_list struct to allow
quirks providing the own methods
For the standard mixer elements, these new callbacks are set to the
standard ones as default, thus there is no functional change by this
patch yet.
The dump and resume callbacks are typedef'ed for ease of later patches
using arrays of such function pointers.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
3360b84b8e