diff options
Diffstat (limited to 'drivers/usb/serial/ipaq.h')
-rw-r--r-- | drivers/usb/serial/ipaq.h | 54 |
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 00000000000..2b9035918b8 --- /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 |