+
+ if (state->mixer->protocol == UAC_VERSION_1) {
+ /* check all control types */
+ for (i = 0; i < 10; i++) {
+ unsigned int ch_bits = 0;
+ for (j = 0; j < channels; j++) {
+ unsigned int mask = snd_usb_combine_bytes(bmaControls + csize * (j+1), csize);
+ if (mask & (1 << i))
+ ch_bits |= (1 << j);
+ }
+ /* audio class v1 controls are never read-only */
+ if (ch_bits & 1) /* the first channel must be set (for ease of programming) */
+ build_feature_ctl(state, _ftr, ch_bits, i, &iterm, unitid, 0);
+ if (master_bits & (1 << i))
+ build_feature_ctl(state, _ftr, 0, i, &iterm, unitid, 0);
+ }
+ } else { /* UAC_VERSION_2 */
+ for (i = 0; i < 30/2; i++) {
+ /* From the USB Audio spec v2.0:
+ bmaControls() is a (ch+1)-element array of 4-byte bitmaps,
+ each containing a set of bit pairs. If a Control is present,
+ it must be Host readable. If a certain Control is not
+ present then the bit pair must be set to 0b00.
+ If a Control is present but read-only, the bit pair must be
+ set to 0b01. If a Control is also Host programmable, the bit
+ pair must be set to 0b11. The value 0b10 is not allowed. */
+ unsigned int ch_bits = 0;
+ unsigned int ch_read_only = 0;
+
+ for (j = 0; j < channels; j++) {
+ unsigned int mask = snd_usb_combine_bytes(bmaControls + csize * (j+1), csize);
+ if (mask & (1 << (i * 2))) {
+ ch_bits |= (1 << j);
+ if (~mask & (1 << ((i * 2) + 1)))
+ ch_read_only |= (1 << j);
+ }
+ }
+
+ /* FIXME: the whole unit is read-only if any of the channels is marked read-only */
+ if (ch_bits & 1) /* the first channel must be set (for ease of programming) */
+ build_feature_ctl(state, _ftr, ch_bits, i, &iterm, unitid, !!ch_read_only);
+ if (master_bits & (1 << i * 2))
+ build_feature_ctl(state, _ftr, 0, i, &iterm, unitid,
+ ~master_bits & (1 << ((i * 2) + 1)));