usb: gadget: f_uac2: Support multiple sampling rates

A list of sampling rates can be specified via configfs. All enabled
sampling rates are sent to the USB host on request. When the host
selects a sampling rate, the internal active rate (stored in
struct f_uac2) is updated.

The gadget no longer supports only one frequency. Therefore USB strings
corresponding to the clock sources are renamed from specific Hz value to
general names Input clock/Output clock.

Config strings with single value stay compatible with the previous
version.

Multiple samplerates passed as configuration arrays to g_audio module
when built for f_uac2.
Signed-off-by: Julian Scheel <julian@jusst.de>
Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Link: https://lore.kernel.org/r/20220121155308.48794-6-pavel.hofman@ivitera.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -6,7 +6,7 @@ Description:
 
 		=====================	=======================================
 		c_chmask		capture channel mask
-		c_srate			capture sampling rate
+		c_srate			list of capture sampling rates (comma-separated)
 		c_ssize			capture sample size (bytes)
 		c_sync			capture synchronization type
 					(async/adaptive)
@@ -20,7 +20,7 @@ Description:
 					(in 1/256 dB)
 		fb_max			maximum extra bandwidth in async mode
 		p_chmask		playback channel mask
-		p_srate			playback sampling rate
+		p_srate			list of playback sampling rates (comma-separated)
 		p_ssize			playback sample size (bytes)
 		p_mute_present		playback mute control enable
 		p_volume_present	playback volume control enable

Documentation/usb/gadget-testing.rst

@@ -726,7 +726,7 @@ The uac2 function provides these attributes in its function directory:
 
 	================ ====================================================
 	c_chmask         capture channel mask
-	c_srate          capture sampling rate
+	c_srate          list of capture sampling rates (comma-separated)
 	c_ssize          capture sample size (bytes)
 	c_sync           capture synchronization type (async/adaptive)
 	c_mute_present   capture mute control enable
@@ -736,7 +736,7 @@ The uac2 function provides these attributes in its function directory:
 	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_srate          playback sampling rate
+	p_srate          list of playback sampling rates (comma-separated)
 	p_ssize          playback sample size (bytes)
 	p_mute_present   playback mute control enable
 	p_volume_present playback volume control enable

drivers/usb/gadget/function/u_uac2.h

@@ -14,6 +14,7 @@
 #define U_UAC2_H
 
 #include <linux/usb/composite.h>
+#include "uac_common.h"
 
 #define UAC2_DEF_PCHMASK 0x3
 #define UAC2_DEF_PSRATE 48000
@@ -35,10 +36,10 @@
 struct f_uac2_opts {
 	struct usb_function_instance	func_inst;
 	int				p_chmask;
-	int				p_srate;
+	int				p_srates[UAC_MAX_RATES];
 	int				p_ssize;
 	int				c_chmask;
-	int				c_srate;
+	int				c_srates[UAC_MAX_RATES];
 	int				c_ssize;
 	int				c_sync;
 

drivers/usb/gadget/legacy/audio.c

@@ -26,9 +26,10 @@ module_param(p_chmask, uint, 0444);
 MODULE_PARM_DESC(p_chmask, "Playback Channel Mask");
 
 /* Playback Default 48 KHz */
-static int p_srate = UAC2_DEF_PSRATE;
-module_param(p_srate, uint, 0444);
-MODULE_PARM_DESC(p_srate, "Playback Sampling Rate");
+static int p_srates[UAC_MAX_RATES] = {UAC2_DEF_PSRATE};
+static int p_srates_cnt = 1;
+module_param_array_named(p_srate, p_srates, uint, &p_srates_cnt, 0444);
+MODULE_PARM_DESC(p_srate, "Playback Sampling Rates (array)");
 
 /* Playback Default 16bits/sample */
 static int p_ssize = UAC2_DEF_PSSIZE;
@@ -41,9 +42,10 @@ module_param(c_chmask, uint, 0444);
 MODULE_PARM_DESC(c_chmask, "Capture Channel Mask");
 
 /* Capture Default 64 KHz */
-static int c_srate = UAC2_DEF_CSRATE;
-module_param(c_srate, uint, 0444);
-MODULE_PARM_DESC(c_srate, "Capture Sampling Rate");
+static int c_srates[UAC_MAX_RATES] = {UAC2_DEF_CSRATE};
+static int c_srates_cnt = 1;
+module_param_array_named(c_srate, c_srates, uint, &c_srates_cnt, 0444);
+MODULE_PARM_DESC(c_srate, "Capture Sampling Rates (array)");
 
 /* Capture Default 16bits/sample */
 static int c_ssize = UAC2_DEF_CSSIZE;
@@ -237,6 +239,7 @@ static int audio_bind(struct usb_composite_dev *cdev)
 {
 #ifndef CONFIG_GADGET_UAC1
 	struct f_uac2_opts	*uac2_opts;
+	int i;
 #else
 #ifndef CONFIG_GADGET_UAC1_LEGACY
 	struct f_uac1_opts	*uac1_opts;
@@ -263,10 +266,16 @@ static int audio_bind(struct usb_composite_dev *cdev)
 #ifndef CONFIG_GADGET_UAC1
 	uac2_opts = container_of(fi_uac2, struct f_uac2_opts, func_inst);
 	uac2_opts->p_chmask = p_chmask;
-	uac2_opts->p_srate = p_srate;
+
+	for (i = 0; i < p_srates_cnt; ++i)
+		uac2_opts->p_srates[i] = p_srates[i];
+
 	uac2_opts->p_ssize = p_ssize;
 	uac2_opts->c_chmask = c_chmask;
-	uac2_opts->c_srate = c_srate;
+
+	for (i = 0; i < c_srates_cnt; ++i)
+		uac2_opts->c_srates[i] = c_srates[i];
+
 	uac2_opts->c_ssize = c_ssize;
 	uac2_opts->req_number = UAC2_DEF_REQ_NUM;
 #else