[PATCH 05/28] ALSA: usb-audio: Refactor usb_audio_make_longname() to use seq_buf

[Bill Wendling <morbo@google.com>]

usb_audio_make_longname() builds card->longname incrementally from the
vendor/manufacturer name, shortname, USB device path, and USB speed using
strscpy(), strlcat(), and manual buffer offset calculations for
usb_make_path().

In preparation for removing the deprecated strlcat() API[1], refactor
usb_audio_make_longname() to use struct seq_buf to track the buffer
position and remaining space across these operations.

Link: https://github.com/KSPP/linux/issues/370 [1]
Cc: codemender-patching+linux@google.com
Assisted-by: Gemini:3.5-pro [git, make, checkpatch]
Signed-off-by: Bill Wendling <morbo@google.com>
---
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---
 sound/usb/card.c | 58 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 39 insertions(+), 19 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 9307da95efbe..bdca8085fca6 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -25,6 +25,7 @@
 #include <linux/list.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/seq_buf.h>
 #include <linux/ctype.h>
 #include <linux/usb.h>
 #include <linux/moduleparam.h>
@@ -651,7 +652,9 @@ static void usb_audio_make_longname(struct usb_device *dev,
 	struct snd_card *card = chip->card;
 	const struct usb_audio_device_name *preset;
 	const char *s = NULL;
-	int len;
+	struct seq_buf sb;
+	char *buf;
+	size_t size;
 
 	preset = lookup_device_name(chip->usb_id);
 
@@ -667,44 +670,61 @@ static void usb_audio_make_longname(struct usb_device *dev,
 		s = preset->vendor_name;
 	else if (quirk && quirk->vendor_name)
 		s = quirk->vendor_name;
-	*card->longname = 0;
-	if (s && *s)
-		strscpy(card->longname, s);
-	else if (dev->manufacturer && *dev->manufacturer)
-		strscpy(card->longname, dev->manufacturer);
 
-	if (*card->longname) {
-		strim(card->longname);
-		if (*card->longname)
-			strlcat(card->longname, " ", sizeof(card->longname));
+	seq_buf_init(&sb, card->longname, sizeof(card->longname));
+
+	if (s && *s)
+		seq_buf_puts(&sb, s);
+	else if (dev->manufacturer && *dev->manufacturer)
+		seq_buf_puts(&sb, dev->manufacturer);
+
+	if (seq_buf_used(&sb)) {
+		char *trimmed;
+
+		seq_buf_str(&sb);
+		trimmed = strim(card->longname);
+		if (trimmed != card->longname)
+			memmove(card->longname, trimmed, strlen(trimmed) + 1);
+		sb.len = strlen(card->longname);
+		if (sb.len)
+			seq_buf_putc(&sb, ' ');
 	}
 
-	strlcat(card->longname, card->shortname, sizeof(card->longname));
+	seq_buf_puts(&sb, card->shortname);
 
-	len = strlcat(card->longname, " at ", sizeof(card->longname));
+	seq_buf_puts(&sb, " at ");
 
-	if (len < sizeof(card->longname))
-		usb_make_path(dev, card->longname + len, sizeof(card->longname) - len);
+	size = seq_buf_get_buf(&sb, &buf);
+	if (size > 0) {
+		int path_len = usb_make_path(dev, buf, size);
+
+		if (path_len >= 0)
+			seq_buf_commit(&sb, path_len);
+		else
+			seq_buf_set_overflow(&sb);
+	}
 
 	switch (snd_usb_get_speed(dev)) {
 	case USB_SPEED_LOW:
-		strlcat(card->longname, ", low speed", sizeof(card->longname));
+		seq_buf_puts(&sb, ", low speed");
 		break;
 	case USB_SPEED_FULL:
-		strlcat(card->longname, ", full speed", sizeof(card->longname));
+		seq_buf_puts(&sb, ", full speed");
 		break;
 	case USB_SPEED_HIGH:
-		strlcat(card->longname, ", high speed", sizeof(card->longname));
+		seq_buf_puts(&sb, ", high speed");
 		break;
 	case USB_SPEED_SUPER:
-		strlcat(card->longname, ", super speed", sizeof(card->longname));
+		seq_buf_puts(&sb, ", super speed");
 		break;
 	case USB_SPEED_SUPER_PLUS:
-		strlcat(card->longname, ", super speed plus", sizeof(card->longname));
+		seq_buf_puts(&sb, ", super speed plus");
 		break;
 	default:
 		break;
 	}
+
+	seq_buf_str(&sb);
 }
 
 static void snd_usb_init_quirk_flags(int idx, struct snd_usb_audio *chip)
-- 
2.55.0.1032.g73a4cd73de-goog