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path: root/drivers/usb/gadget/usbstring.c
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Diffstat (limited to 'drivers/usb/gadget/usbstring.c')
-rw-r--r--drivers/usb/gadget/usbstring.c91
1 files changed, 91 insertions, 0 deletions
diff --git a/drivers/usb/gadget/usbstring.c b/drivers/usb/gadget/usbstring.c
new file mode 100644
index 0000000000..75f6f99f81
--- /dev/null
+++ b/drivers/usb/gadget/usbstring.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: LGPL-2.1+
+/*
+ * Copyright (C) 2003 David Brownell
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/string.h>
+#include <linux/device.h>
+#include <linux/nls.h>
+
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+
+
+/**
+ * usb_gadget_get_string - fill out a string descriptor
+ * @table: of c strings encoded using UTF-8
+ * @id: string id, from low byte of wValue in get string descriptor
+ * @buf: at least 256 bytes, must be 16-bit aligned
+ *
+ * Finds the UTF-8 string matching the ID, and converts it into a
+ * string descriptor in utf16-le.
+ * Returns length of descriptor (always even) or negative errno
+ *
+ * If your driver needs stings in multiple languages, you'll probably
+ * "switch (wIndex) { ... }" in your ep0 string descriptor logic,
+ * using this routine after choosing which set of UTF-8 strings to use.
+ * Note that US-ASCII is a strict subset of UTF-8; any string bytes with
+ * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
+ * characters (which are also widely used in C strings).
+ */
+int
+usb_gadget_get_string (const struct usb_gadget_strings *table, int id, u8 *buf)
+{
+ struct usb_string *s;
+ int len;
+
+ /* descriptor 0 has the language id */
+ if (id == 0) {
+ buf [0] = 4;
+ buf [1] = USB_DT_STRING;
+ buf [2] = (u8) table->language;
+ buf [3] = (u8) (table->language >> 8);
+ return 4;
+ }
+ for (s = table->strings; s && s->s; s++)
+ if (s->id == id)
+ break;
+
+ /* unrecognized: stall. */
+ if (!s || !s->s)
+ return -EINVAL;
+
+ /* string descriptors have length, tag, then UTF16-LE text */
+ len = min((size_t)USB_MAX_STRING_LEN, strlen(s->s));
+ len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
+ (wchar_t *) &buf[2], USB_MAX_STRING_LEN);
+ if (len < 0)
+ return -EINVAL;
+ buf [0] = (len + 1) * 2;
+ buf [1] = USB_DT_STRING;
+ return buf [0];
+}
+EXPORT_SYMBOL_GPL(usb_gadget_get_string);
+
+/**
+ * usb_validate_langid - validate usb language identifiers
+ * @langid: usb language identifier
+ *
+ * Returns true for valid language identifier, otherwise false.
+ */
+bool usb_validate_langid(u16 langid)
+{
+ u16 primary_lang = langid & 0x3ff; /* bit [9:0] */
+ u16 sub_lang = langid >> 10; /* bit [15:10] */
+
+ switch (primary_lang) {
+ case 0:
+ case 0x62 ... 0xfe:
+ case 0x100 ... 0x3ff:
+ return false;
+ }
+ if (!sub_lang)
+ return false;
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(usb_validate_langid);