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 35 struct ipaq_packet { 36 char *data; 37 size_t len; 38 size_t written; 39 struct list_head list; 40 }; 41 42 struct 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