controller/Output/pjrcUSB/arm/usb_mem.c

/* 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();
}