1 /* Teensyduino Core Library
2 * http://www.pjrc.com/teensy/
3 * Copyright (c) 2013 PJRC.COM, LLC.
4 * Modifications by Jacob Alexander (2013-2014)
6 * Permission is hereby granted, free of charge, to any person obtaining
7 * a copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sublicense, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
14 * 1. The above copyright notice and this permission notice shall be
15 * included in all copies or substantial portions of the Software.
17 * 2. If the Software is incorporated into a build system that allows
18 * selection among a list of target devices, then similar target
19 * devices manufactured by PJRC.COM must be included in the list of
20 * target devices and selectable in the same manner.
22 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
23 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
24 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
25 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
26 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
27 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
28 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
32 // ----- Includes -----
35 #include <Lib/OutputLib.h>
43 // ----- Variables -----
45 __attribute__ ((section(".usbbuffers"), used))
46 unsigned char usb_buffer_memory[ NUM_USB_BUFFERS * sizeof(usb_packet_t) ];
48 static uint32_t usb_buffer_available = 0xFFFFFFFF;
52 // ----- Externs -----
54 extern void usb_rx_memory( usb_packet_t *packet );
56 // for the receive endpoints to request memory
57 extern uint8_t usb_rx_memory_needed;
61 // ----- Functions -----
63 // use bitmask and CLZ instruction to implement fast free list
64 // http://www.archivum.info/gnu.gcc.help/2006-08/00148/Re-GCC-Inline-Assembly.html
65 // http://gcc.gnu.org/ml/gcc/2012-06/msg00015.html
68 usb_packet_t *usb_malloc()
70 unsigned int n, avail;
74 avail = usb_buffer_available;
75 n = __builtin_clz( avail ); // clz = count leading zeros
76 if ( n >= NUM_USB_BUFFERS )
82 usb_buffer_available = avail & ~(0x80000000 >> n);
84 p = usb_buffer_memory + ( n * sizeof(usb_packet_t) );
86 *(uint32_t *)(p + 4) = 0;
87 return (usb_packet_t *)p;
91 void usb_free( usb_packet_t *p )
95 n = ( (uint8_t *)p - usb_buffer_memory ) / sizeof(usb_packet_t);
96 if ( n >= NUM_USB_BUFFERS )
99 // if any endpoints are starving for memory to receive
100 // packets, give this memory to them immediately!
101 if ( usb_rx_memory_needed && usb_configuration )
107 mask = (0x80000000 >> n);
109 usb_buffer_available |= mask;