Desktop/xinu_mips-1.0.2.tar/xinu_mips-1.0.2/uart/uartRead.c

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/* Embedded XINU, Copyright (C) 2007.  All rights reserved. */

#include <kernel.h>
#include <uart.h>
#include <device.h>

devcall uartRead(device *pdev, unsigned char *buf, int len)
{
        irqmask ps;
        int count = 0;
        char c;
        struct uart *puart;

        /* Setup and error check pointers to structures */
        ASSERT(NULL != pdev);
        puart = (struct uart *)pdev->controlblk;
        ASSERT(puart != NULL);

        ps = disable();

        /* If in non-blocking mode, ensure there is */
    /* enough input for the entire read request */
        if(puart->iflags & UART_IFLAG_NOBLOCK)
        {
                if (scount(puart->isema) < len)
                        {  restore(ps); return SYSERR;  }
        }

        /* Put each character into the buffer from the input buffer */
        while (count < len)
        {
                /* If in non-blocking mode, ensure there is another byte of input */
                if(puart->iflags & UART_IFLAG_NOBLOCK)
                {
                        if (scount(puart->isema) < 1)
                                {  break;  }
                }

                /* Wait for input and read character from the  */
                /* input buffer; Preserve the circular buffer  */
                wait(puart->isema);
                c = puart->in[puart->istart];
                *buf++ = c;
                puart->icount--;
                puart->istart = (puart->istart + 1) % UART_IBLEN;
                count++;

                /* If echo is enabled, echo the character */
                if (puart->iflags & UART_IFLAG_ECHO)
                        { uartPutChar(puart->dev,c); }
        }

        restore(ps);
        return count;
}

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