1/*
2 * USB Compaq iPAQ driver
3 *
4 *	Copyright (C) 2001 - 2002
5 *	    Ganesh Varadarajan <ganesh@veritas.com>
6 *
7 *	This program is free software; you can redistribute it and/or modify
8 *	it under the terms of the GNU General Public License as published by
9 *	the Free Software Foundation; either version 2 of the License, or
10 *	(at your option) any later version.
11 *
12 */
13
14#ifndef __LINUX_USB_SERIAL_IPAQ_H
15#define __LINUX_USB_SERIAL_IPAQ_H
16
17/*
18 * Since we can't queue our bulk write urbs (don't know why - it just
19 * doesn't work), we can send down only one write urb at a time. The simplistic
20 * approach taken by the generic usbserial driver will work, but it's not good
21 * for performance. Therefore, we buffer upto URBDATA_QUEUE_MAX bytes of write
22 * requests coming from the line discipline. This is done by chaining them
23 * in lists of struct ipaq_packet, each packet holding a maximum of
24 * PACKET_SIZE bytes.
25 *
26 * ipaq_write() can be called from bottom half context; hence we can't
27 * allocate memory for packets there. So we initialize a pool of packets at
28 * the first open and maintain a freelist.
29 *
30 * The value of PACKET_SIZE was empirically determined by
31 * checking the maximum write sizes sent down by the ppp ldisc.
32 * URBDATA_QUEUE_MAX is set to 64K, which is the maximum TCP window size.
33 */
34
35struct ipaq_packet {
36	char			*data;
37	size_t			len;
38	size_t			written;
39	struct list_head	list;
40};
41
42struct ipaq_private {
43	int			active;
44	int			queue_len;
45	int			free_len;
46	struct list_head	queue;
47	struct list_head	freelist;
48};
49
50#define URBDATA_SIZE		4096
51#define URBDATA_QUEUE_MAX	(64 * 1024)
52#define PACKET_SIZE		256
53
54#endif
55