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-rw-r--r--drivers/usb/serial/ipaq.h54
1 files changed, 54 insertions, 0 deletions
diff --git a/drivers/usb/serial/ipaq.h b/drivers/usb/serial/ipaq.h
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+++ b/drivers/usb/serial/ipaq.h
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+/*
+ * 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