usb: gadget: f_uac2: Expose all string descriptors through configfs.

This makes all string descriptors configurable for the UAC2 gadget
so the user can configure names of terminals and controls. Alt mode
names are not included for now and will be in future work related
to adding alternate settings.

discussion thread for api changes for alt mode settings:
https://lore.kernel.org/linux-usb/[e-mail]/T/

Signed-off-by: Chris Wulff <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

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

···
 		req_number		the number of pre-allocated requests
 					for both capture and playback
 		function_name		name of the interface
+		if_ctrl_name		topology control name
+		clksrc_in_name		input clock name
+		clksrc_out_name		output clock name
+		p_it_name		playback input terminal name
+		p_it_ch_name		playback input first channel name
+		p_ot_name		playback output terminal name
+		p_fu_vol_name		playback mute/volume function unit name
+		c_it_name		capture input terminal name
+		c_it_ch_name		capture input first channel name
+		c_ot_name		capture output terminal name
+		c_fu_vol_name		capture mute/volume functional unit name
 		c_terminal_type		code of the capture terminal type
 		p_terminal_type		code of the playback terminal type
 		=====================	=======================================

Documentation/usb/gadget-testing.rst

···
 	req_number       the number of pre-allocated request for both capture
 	                 and playback
 	function_name    name of the interface
+	if_ctrl_name     topology control name
+	clksrc_in_name   input clock name
+	clksrc_out_name  output clock name
+	p_it_name        playback input terminal name
+	p_it_ch_name     playback input first channel name
+	p_ot_name        playback output terminal name
+	p_fu_vol_name    playback function unit name
+	c_it_name        capture input terminal name
+	c_it_ch_name     capture input first channel name
+	c_ot_name        capture output terminal name
+	c_fu_vol_name    capture functional unit name
 	c_terminal_type  code of the capture terminal type
 	p_terminal_type  code of the playback terminal type
 	================ ====================================================

drivers/usb/gadget/function/f_uac2.c

···
 	STR_CLKSRC_IN,
 	STR_CLKSRC_OUT,
 	STR_USB_IT,
+	STR_USB_IT_CH,
 	STR_IO_IT,
+	STR_IO_IT_CH,
 	STR_USB_OT,
 	STR_IO_OT,
 	STR_FU_IN,
···
 	STR_AS_OUT_ALT1,
 	STR_AS_IN_ALT0,
 	STR_AS_IN_ALT1,
+	NUM_STR_DESCRIPTORS,
 };
 
-static struct usb_string strings_fn[] = {
-	/* [STR_ASSOC].s = DYNAMIC, */
-	[STR_IF_CTRL].s = "Topology Control",
-	[STR_CLKSRC_IN].s = "Input Clock",
-	[STR_CLKSRC_OUT].s = "Output Clock",
-	[STR_USB_IT].s = "USBH Out",
-	[STR_IO_IT].s = "USBD Out",
-	[STR_USB_OT].s = "USBH In",
-	[STR_IO_OT].s = "USBD In",
-	[STR_FU_IN].s = "Capture Volume",
-	[STR_FU_OUT].s = "Playback Volume",
-	[STR_AS_OUT_ALT0].s = "Playback Inactive",
-	[STR_AS_OUT_ALT1].s = "Playback Active",
-	[STR_AS_IN_ALT0].s = "Capture Inactive",
-	[STR_AS_IN_ALT1].s = "Capture Active",
-	{ },
-};
+static struct usb_string strings_fn[NUM_STR_DESCRIPTORS + 1] = {};
 
 static const char *const speed_names[] = {
 	[USB_SPEED_UNKNOWN] = "UNKNOWN",
···
 		return ret;
 
 	strings_fn[STR_ASSOC].s = uac2_opts->function_name;
+	strings_fn[STR_IF_CTRL].s = uac2_opts->if_ctrl_name;
+	strings_fn[STR_CLKSRC_IN].s = uac2_opts->clksrc_in_name;
+	strings_fn[STR_CLKSRC_OUT].s = uac2_opts->clksrc_out_name;
+
+	strings_fn[STR_USB_IT].s = uac2_opts->c_it_name;
+	strings_fn[STR_USB_IT_CH].s = uac2_opts->c_it_ch_name;
+	strings_fn[STR_IO_OT].s = uac2_opts->c_ot_name;
+	strings_fn[STR_FU_OUT].s = uac2_opts->c_fu_vol_name;
+	strings_fn[STR_AS_OUT_ALT0].s = "Playback Inactive";
+	strings_fn[STR_AS_OUT_ALT1].s = "Playback Active";
+
+	strings_fn[STR_IO_IT].s = uac2_opts->p_it_name;
+	strings_fn[STR_IO_IT_CH].s = uac2_opts->p_it_ch_name;
+	strings_fn[STR_USB_OT].s = uac2_opts->p_ot_name;
+	strings_fn[STR_FU_IN].s = uac2_opts->p_fu_vol_name;
+	strings_fn[STR_AS_IN_ALT0].s = "Capture Inactive";
+	strings_fn[STR_AS_IN_ALT1].s = "Capture Active";
 
 	us = usb_gstrings_attach(cdev, fn_strings, ARRAY_SIZE(strings_fn));
 	if (IS_ERR(us))
···
 	in_clk_src_desc.iClockSource = us[STR_CLKSRC_IN].id;
 	out_clk_src_desc.iClockSource = us[STR_CLKSRC_OUT].id;
 	usb_out_it_desc.iTerminal = us[STR_USB_IT].id;
+	usb_out_it_desc.iChannelNames = us[STR_USB_IT_CH].id;
 	io_in_it_desc.iTerminal = us[STR_IO_IT].id;
+	io_in_it_desc.iChannelNames = us[STR_IO_IT_CH].id;
 	usb_in_ot_desc.iTerminal = us[STR_USB_OT].id;
 	io_out_ot_desc.iTerminal = us[STR_IO_OT].id;
 	std_as_out_if0_desc.iInterface = us[STR_AS_OUT_ALT0].id;
···
 UAC2_ATTRIBUTE(s16, c_volume_res);
 UAC2_ATTRIBUTE(u32, fb_max);
 UAC2_ATTRIBUTE_STRING(function_name);
+UAC2_ATTRIBUTE_STRING(if_ctrl_name);
+UAC2_ATTRIBUTE_STRING(clksrc_in_name);
+UAC2_ATTRIBUTE_STRING(clksrc_out_name);
+
+UAC2_ATTRIBUTE_STRING(p_it_name);
+UAC2_ATTRIBUTE_STRING(p_it_ch_name);
+UAC2_ATTRIBUTE_STRING(p_ot_name);
+UAC2_ATTRIBUTE_STRING(p_fu_vol_name);
+
+UAC2_ATTRIBUTE_STRING(c_it_name);
+UAC2_ATTRIBUTE_STRING(c_it_ch_name);
+UAC2_ATTRIBUTE_STRING(c_ot_name);
+UAC2_ATTRIBUTE_STRING(c_fu_vol_name);
 
 UAC2_ATTRIBUTE(s16, p_terminal_type);
 UAC2_ATTRIBUTE(s16, c_terminal_type);
+
 
 static struct configfs_attribute *f_uac2_attrs[] = {
 	&f_uac2_opts_attr_p_chmask,
···
 	&f_uac2_opts_attr_c_volume_res,
 
 	&f_uac2_opts_attr_function_name,
+	&f_uac2_opts_attr_if_ctrl_name,
+	&f_uac2_opts_attr_clksrc_in_name,
+	&f_uac2_opts_attr_clksrc_out_name,
+
+	&f_uac2_opts_attr_p_it_name,
+	&f_uac2_opts_attr_p_it_ch_name,
+	&f_uac2_opts_attr_p_ot_name,
+	&f_uac2_opts_attr_p_fu_vol_name,
+
+	&f_uac2_opts_attr_c_it_name,
+	&f_uac2_opts_attr_c_it_ch_name,
+	&f_uac2_opts_attr_c_ot_name,
+	&f_uac2_opts_attr_c_fu_vol_name,
 
 	&f_uac2_opts_attr_p_terminal_type,
 	&f_uac2_opts_attr_c_terminal_type,
···
 	opts->fb_max = FBACK_FAST_MAX;
 
 	scnprintf(opts->function_name, sizeof(opts->function_name), "Source/Sink");
+	scnprintf(opts->if_ctrl_name, sizeof(opts->if_ctrl_name), "Topology Control");
+	scnprintf(opts->clksrc_in_name, sizeof(opts->clksrc_in_name), "Input Clock");
+	scnprintf(opts->clksrc_out_name, sizeof(opts->clksrc_out_name), "Output Clock");
+
+	scnprintf(opts->p_it_name, sizeof(opts->p_it_name), "USBD Out");
+	scnprintf(opts->p_it_ch_name, sizeof(opts->p_it_ch_name), "Capture Channels");
+	scnprintf(opts->p_ot_name, sizeof(opts->p_ot_name), "USBH In");
+	scnprintf(opts->p_fu_vol_name, sizeof(opts->p_fu_vol_name), "Capture Volume");
+
+	scnprintf(opts->c_it_name, sizeof(opts->c_it_name), "USBH Out");
+	scnprintf(opts->c_it_ch_name, sizeof(opts->c_it_ch_name), "Playback Channels");
+	scnprintf(opts->c_ot_name, sizeof(opts->c_ot_name), "USBD In");
+	scnprintf(opts->c_fu_vol_name, sizeof(opts->c_fu_vol_name), "Playback Volume");
 
 	opts->p_terminal_type = UAC2_DEF_P_TERM_TYPE;
 	opts->c_terminal_type = UAC2_DEF_C_TERM_TYPE;

drivers/usb/gadget/function/u_uac2.h

···
 	int				fb_max;
 	bool			bound;
 
-	char			function_name[32];
+	char			function_name[USB_MAX_STRING_LEN];
+	char			if_ctrl_name[USB_MAX_STRING_LEN];
+	char			clksrc_in_name[USB_MAX_STRING_LEN];
+	char			clksrc_out_name[USB_MAX_STRING_LEN];
+
+	char			p_it_name[USB_MAX_STRING_LEN];
+	char			p_it_ch_name[USB_MAX_STRING_LEN];
+	char			p_ot_name[USB_MAX_STRING_LEN];
+	char			p_fu_vol_name[USB_MAX_STRING_LEN];
+
+	char			c_it_name[USB_MAX_STRING_LEN];
+	char			c_it_ch_name[USB_MAX_STRING_LEN];
+	char			c_ot_name[USB_MAX_STRING_LEN];
+	char			c_fu_vol_name[USB_MAX_STRING_LEN];
 
 	s16				p_terminal_type;
 	s16				c_terminal_type;