Pirelli's fw offers 10 audio output volume levels selectable via volume up/down
keys.  Cycling through these volume levels on the idle screen and reading out
Iota VBDCTRL register (fc-tmsh abbr 0 6) at each level yields the following
table:

Volume level	VBDCTRL		Vol	PGA	Total
-----------------------------------------------------
1		047		-18	+1	-17
2		04A		-18	+4	-14
3		006		-12	0	-12
4		008		-12	+2	-10
5		00A		-12	+4	-8
6		067		-6	+1	-5
7		06A		-6	+4	-2
8		026		0	0	0
9		028		0	+2	+2
10		02A		0	+4	+4

In an active call in handheld (earpiece output) mode, the above relation of
selectable volume level to VBDCTRL remains the same.  However, when the
loudspeaker is turned on in a call, the mapping changes to the following:

Volume level	VBDCTRL		Vol	PGA	Total
-----------------------------------------------------
1		046		-18	0	-18
2		049		-18	+3	-15
3		005		-12	-1	-13
4		007		-12	+1	-11
5		009		-12	+3	-9
6		066		-6	0	-6
7		069		-6	+3	-3
8		025		0	-1	-1
9		027		0	+1	+1
10		029		0	+3	+3

Plugging in Pirelli's wired headset and cycling through volume levels on the
idle screen, we get this:

Volume level	VBDCTRL		Vol	PGA	Total
-----------------------------------------------------
1		045		-18	-1	-19
2		048		-18	+2	-16
3		004		-12	-2	-14
4		006		-12	0	-12
5		008		-12	+2	-10
6		065		-6	-1	-7
7		068		-6	+2	-4
8		024		0	-2	-2
9		026		0	0	0
10		028		0	+2	+2

In-call state in headset mode follows the same mapping as headset mode idle
screen.  If the user turns on the loudspeaker while in a call with the headset
inserted, the volume table becomes that of the loudspeaker mode, not the
headset mode.