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controller/Output/pjrcUSB/arm/usb_mem.c

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