1 files changed, 54 insertions, 0 deletions
diff --git a/drivers/usb/serial/ipaq.h b/drivers/usb/serial/ipaq.h
new file mode 100644
index 000000000000..2b9035918b85
--- /dev/null
+++ b/drivers/usb/serial/ipaq.h
@@ -0,0 +1,54 @@
+/*
+ * USB Compaq iPAQ driver
+ *
+ *	Copyright (C) 2001 - 2002
+ *	    Ganesh Varadarajan <ganesh@veritas.com>
+ *
+ *	This program is free software; you can redistribute it and/or modify
+ *	it under the terms of the GNU General Public License as published by
+ *	the Free Software Foundation; either version 2 of the License, or
+ *	(at your option) any later version.
+ *
+ */
+
+#ifndef __LINUX_USB_SERIAL_IPAQ_H
+#define __LINUX_USB_SERIAL_IPAQ_H
+
+/*
+ * Since we can't queue our bulk write urbs (don't know why - it just
+ * doesn't work), we can send down only one write urb at a time. The simplistic
+ * approach taken by the generic usbserial driver will work, but it's not good
+ * for performance. Therefore, we buffer upto URBDATA_QUEUE_MAX bytes of write
+ * requests coming from the line discipline. This is done by chaining them
+ * in lists of struct ipaq_packet, each packet holding a maximum of
+ * PACKET_SIZE bytes.
+ *
+ * ipaq_write() can be called from bottom half context; hence we can't
+ * allocate memory for packets there. So we initialize a pool of packets at
+ * the first open and maintain a freelist.
+ *
+ * The value of PACKET_SIZE was empirically determined by
+ * checking the maximum write sizes sent down by the ppp ldisc.
+ * URBDATA_QUEUE_MAX is set to 64K, which is the maximum TCP window size.
+ */
+
+struct ipaq_packet {
+	char			*data;
+	size_t			len;
+	size_t			written;
+	struct list_head	list;
+};
+
+struct ipaq_private {
+	int			active;
+	int			queue_len;
+	int			free_len;
+	struct list_head	queue;
+	struct list_head	freelist;
+};
+
+#define URBDATA_SIZE		4096
+#define URBDATA_QUEUE_MAX	(64 * 1024)
+#define PACKET_SIZE		256
+
+#endif