/** @file dma_mbuf.h
 * Module handling Direct Memory Access controller's multibuffer system
 *
 * The module provides a convenient tool to send data to a peripheral in a
 * buffered, low-altency, low-cpu usage, non-blocking way
 */

//--includes--------------------------------------------------------------------

#include "dma_mbuf.h"


//--local definitions-----------------------------------------------------------

#define DMA_CONFIG (DMA_CONFIG_IRQ_COMPLETE | DMA_CONFIG_FROM_MEM \
					| DMA_CONFIG_INC_MEM | DMA_CONFIG_PSIZE_8BITS \
					| DMA_CONFIG_MSIZE_8BITS)

static void mbuf_callback(enum DmaIRQSource src, volatile void* param);


//--local variables-------------------------------------------------------------

//--public functions------------------------------------------------------------

void dma_mbuf_configure(volatile struct DmaMultiBuffer* buffer,
		const struct DmaParam* param, enum DmaConfig priority,
		void* raw_buffer, uint16_t buffer_size)
{
	#warning "check for null ptr"

	buffer->raw_buffer = raw_buffer;

	buffer->param = param;
	buffer->priority = priority;

	buffer->buffer_size = buffer_size / 2;

	buffer->byte_index = 0;
	buffer->buffer_index = 0;

	buffer->dma_running = false;
}

uint32_t dma_mbuf_write_byte(volatile struct DmaMultiBuffer* buffer,
		uint8_t byte)
{
	//if the current buffer is full, give up
	if (buffer->byte_index >= buffer->buffer_size) {
		return 1;
	}

	//write the byte
	buffer->raw_buffer[buffer->buffer_index * buffer->buffer_size
		+ buffer->byte_index] = byte;
	++buffer->byte_index;
	return 0;
}

void dma_mbuf_switch(volatile struct DmaMultiBuffer* buffer)
{
	//if transfer already in progress or no data to send, don't start the
	//transfer
	if (buffer->dma_running || buffer->byte_index == 0) {
		return;
	}

	//start a new transfer
	dma_configure(buffer->param->dma, buffer->param->channel,
			DMA_CONFIG | buffer->param->config | buffer->priority,
			buffer->param->periph,
			&buffer->raw_buffer[buffer->buffer_index * buffer->buffer_size],
			buffer->byte_index, mbuf_callback, buffer);
	buffer->dma_running = true;

	buffer->byte_index = 0;
	++buffer->buffer_index;
	if (buffer->buffer_index > 1) {
		buffer->buffer_index = 0;
	}

	return;
}


//--local functions-------------------------------------------------------------

/**
 * Callback called on DMA TX tranfert's completion. Checks for any remaining
 * data to send. If any, starts a new transfer, else stop the DMA
 */
static void mbuf_callback(enum DmaIRQSource src, volatile void* param)
{
	(void)src; //only transfer complete expected
	volatile struct DmaMultiBuffer* buffer = param;

	buffer->dma_running = false;
}