Merge pull request #40 from MultiTracksDotCom/develop

Merge develop into main (0.1.1) Alpha

Author: ardentra

Documentation/ABI/testing/configfs-usb-gadget-uac2

@@ -5,7 +5,15 @@ Description:
 		The attributes:
 
 		=====================	=======================================
-		c_chmask		capture channel mask
+		c_chmask		capture channel mask; bits 0-26 correspond
+					to the UAC2 spatial channel positions (UAC2
+					spec 4.1 Table 4-1). Masks that stay within
+					bits 0-26 are used directly as bmChannelConfig
+					in the USB descriptor. Any bit set outside
+					0-26 triggers non-predefined spatial location
+					mode (bmChannelConfig=0), which allows more
+					than 27 channels; the channel count equals
+					popcount(c_chmask) in both cases.
 		c_srate			list of capture sampling rates (comma-separated)
 		c_ssize			capture sample size (bytes)
 		c_hs_bint		capture bInterval for HS/SS (1-4: fixed, 0: auto)
@@ -20,7 +28,8 @@ Description:
 		c_volume_res		capture volume control resolution
 					(in 1/256 dB)
 		fb_max			maximum extra bandwidth in async mode
-		p_chmask		playback channel mask
+		p_chmask		playback channel mask; same semantics as
+					c_chmask above
 		p_srate			list of playback sampling rates (comma-separated)
 		p_ssize			playback sample size (bytes)
 		p_hs_bint		playback bInterval for HS/SS (1-4: fixed, 0: auto)

drivers/usb/gadget/function/f_uac2.c

@@ -989,10 +989,6 @@ static int afunc_validate_opts(struct g_audio *agdev, struct device *dev)
 
 	if (!opts->p_chmask && !opts->c_chmask)
 		msg = "no playback and capture channels";
-	else if (opts->p_chmask & ~UAC2_CHANNEL_MASK)
-		msg = "unsupported playback channels mask";
-	else if (opts->c_chmask & ~UAC2_CHANNEL_MASK)
-		msg = "unsupported capture channels mask";
 	else if ((opts->p_ssize < 1) || (opts->p_ssize > 4))
 		msg = "incorrect playback sample size";
 	else if ((opts->c_ssize < 1) || (opts->c_ssize > 4))
@@ -1090,14 +1086,25 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
 
 
 	/* Initialize the configurable parameters */
+	/*
+	 * UAC2 spec §4.1: bmChannelConfig bits 27-30 are reserved and must be
+	 * zero. For channel masks that exceed the 27 defined spatial positions
+	 * (bits 0-26), use bmChannelConfig=0 (non-predefined spatial locations)
+	 * with bNrChannels set from the popcount of the full mask. This is the
+	 * standard-compliant way to declare more than 27 channels.
+	 */
+	u32 c_chanconfig = (uac2_opts->c_chmask & ~UAC2_CHANNEL_MASK) ?
+		0 : uac2_opts->c_chmask;
+	u32 p_chanconfig = (uac2_opts->p_chmask & ~UAC2_CHANNEL_MASK) ?
+		0 : uac2_opts->p_chmask;
 	usb_out_it_desc.bNrChannels = num_channels(uac2_opts->c_chmask);
-	usb_out_it_desc.bmChannelConfig = cpu_to_le32(uac2_opts->c_chmask);
+	usb_out_it_desc.bmChannelConfig = cpu_to_le32(c_chanconfig);
 	io_in_it_desc.bNrChannels = num_channels(uac2_opts->p_chmask);
-	io_in_it_desc.bmChannelConfig = cpu_to_le32(uac2_opts->p_chmask);
+	io_in_it_desc.bmChannelConfig = cpu_to_le32(p_chanconfig);
 	as_out_hdr_desc.bNrChannels = num_channels(uac2_opts->c_chmask);
-	as_out_hdr_desc.bmChannelConfig = cpu_to_le32(uac2_opts->c_chmask);
+	as_out_hdr_desc.bmChannelConfig = cpu_to_le32(c_chanconfig);
 	as_in_hdr_desc.bNrChannels = num_channels(uac2_opts->p_chmask);
-	as_in_hdr_desc.bmChannelConfig = cpu_to_le32(uac2_opts->p_chmask);
+	as_in_hdr_desc.bmChannelConfig = cpu_to_le32(p_chanconfig);
 	as_out_fmt1_desc.bSubslotSize = uac2_opts->c_ssize;
 	as_out_fmt1_desc.bBitResolution = uac2_opts->c_ssize * 8;
 	as_in_fmt1_desc.bSubslotSize = uac2_opts->p_ssize;