blob: 2b9035918b85bac1e7855a81860aeaf77ad3705c (
plain) (
tree)
|
|
/*
* 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
|
