usb: gadget: uvc: Generalise helper functions for reuse

The __uvcg_*frm_intrv() helper functions can be helpful when adding
support for similar attributes. Generalise the functions and
move them higher in the file for better coverage.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20230206161802.892954-3-dan.scally@ideasonboard.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/uvc_configfs.c

@@ -47,6 +47,71 @@ static int uvcg_config_compare_u32(const void *l, const void *r)
 	return li < ri ? -1 : li == ri ? 0 : 1;
 }
 
+static inline int __uvcg_count_item_entries(char *buf, void *priv, unsigned int size)
+{
+	++*((int *)priv);
+	return 0;
+}
+
+static inline int __uvcg_fill_item_entries(char *buf, void *priv, unsigned int size)
+{
+	unsigned int num;
+	u8 **values;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &num);
+	if (ret)
+		return ret;
+
+	if (num != (num & GENMASK((size * 8) - 1, 0)))
+		return -ERANGE;
+
+	values = priv;
+	memcpy(*values, &num, size);
+	*values += size;
+
+	return 0;
+}
+
+static int __uvcg_iter_item_entries(const char *page, size_t len,
+				    int (*fun)(char *, void *, unsigned int),
+				    void *priv, unsigned int size)
+{
+	/* sign, base 2 representation, newline, terminator */
+	unsigned int bufsize = 1 + size * 8 + 1 + 1;
+	const char *pg = page;
+	int i, ret = 0;
+	char *buf;
+
+	if (!fun)
+		return -EINVAL;
+
+	buf = kzalloc(bufsize, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	while (pg - page < len) {
+		i = 0;
+		while (i < sizeof(buf) && (pg - page < len) &&
+		       *pg != '\0' && *pg != '\n')
+			buf[i++] = *pg++;
+		if (i == sizeof(buf)) {
+			ret = -EINVAL;
+			goto out_free_buf;
+		}
+		while ((pg - page < len) && (*pg == '\0' || *pg == '\n'))
+			++pg;
+		buf[i] = '\0';
+		ret = fun(buf, priv, size);
+		if (ret)
+			goto out_free_buf;
+	}
+
+out_free_buf:
+	kfree(buf);
+	return ret;
+}
+
 struct uvcg_config_group_type {
 	struct config_item_type type;
 	const char *name;
@@ -1336,57 +1401,6 @@ static ssize_t uvcg_frame_dw_frame_interval_show(struct config_item *item,
 	return result;
 }
 
-static inline int __uvcg_count_frm_intrv(char *buf, void *priv)
-{
-	++*((int *)priv);
-	return 0;
-}
-
-static inline int __uvcg_fill_frm_intrv(char *buf, void *priv)
-{
-	u32 num, **interv;
-	int ret;
-
-	ret = kstrtou32(buf, 0, &num);
-	if (ret)
-		return ret;
-
-	interv = priv;
-	**interv = num;
-	++*interv;
-
-	return 0;
-}
-
-static int __uvcg_iter_frm_intrv(const char *page, size_t len,
-				 int (*fun)(char *, void *), void *priv)
-{
-	/* sign, base 2 representation, newline, terminator */
-	char buf[1 + sizeof(u32) * 8 + 1 + 1];
-	const char *pg = page;
-	int i, ret;
-
-	if (!fun)
-		return -EINVAL;
-
-	while (pg - page < len) {
-		i = 0;
-		while (i < sizeof(buf) && (pg - page < len) &&
-				*pg != '\0' && *pg != '\n')
-			buf[i++] = *pg++;
-		if (i == sizeof(buf))
-			return -EINVAL;
-		while ((pg - page < len) && (*pg == '\0' || *pg == '\n'))
-			++pg;
-		buf[i] = '\0';
-		ret = fun(buf, priv);
-		if (ret)
-			return ret;
-	}
-
-	return 0;
-}
-
 static ssize_t uvcg_frame_dw_frame_interval_store(struct config_item *item,
 						  const char *page, size_t len)
 {
@@ -1410,7 +1424,7 @@ static ssize_t uvcg_frame_dw_frame_interval_store(struct config_item *item,
 		goto end;
 	}
 
-	ret = __uvcg_iter_frm_intrv(page, len, __uvcg_count_frm_intrv, &n);
+	ret = __uvcg_iter_item_entries(page, len, __uvcg_count_item_entries, &n, sizeof(u32));
 	if (ret)
 		goto end;
 
@@ -1420,7 +1434,7 @@ static ssize_t uvcg_frame_dw_frame_interval_store(struct config_item *item,
 		goto end;
 	}
 
-	ret = __uvcg_iter_frm_intrv(page, len, __uvcg_fill_frm_intrv, &tmp);
+	ret = __uvcg_iter_item_entries(page, len, __uvcg_fill_item_entries, &tmp, sizeof(u32));
 	if (ret) {
 		kfree(frm_intrv);
 		goto end;