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

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

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

devcall uartWrite(device *pdev, unsigned char *buf, int len)
{
        irqmask ps;
        int count = 0;
        struct uart *puart;
        volatile struct uart_csreg *pucsr;

        /* Setup and error check pointers to structures */
        if (NULL == pdev)  {   return SYSERR;   }

        puart = (struct uart *)pdev->controlblk;
        if (NULL == puart) {   return SYSERR;   } 

        pucsr = puart->csr;
        if (NULL == pucsr) {   return SYSERR;   }

        ps = disable();

        /* If in non-blocking mode, ensure there is enough space for the entire
         * write request */
        if (puart->oflags & UART_OFLAG_NOBLOCK)
        {
                if (scount(puart->osema) < len) {   restore(ps); return SYSERR;   }
        }

        /* Put each character from the buffer into the output buffer for the
         * lower half */
        while (count < len)
        {
                /* If in non-blocking mode, ensure there is another byte of space
                 * for output */
                if (puart->oflags & UART_OFLAG_NOBLOCK)
                {
                        if (scount(puart->osema) < 1) {   break;   }
                }

                /* If the UART transmitter hardware is idle, write directly to the
                 * hardware */
                if (puart->oidle)
                {
                        puart->oidle = 0;
                        pucsr->thr = *buf++;
                        count++;
                        puart->cout++;
                }
                /* Wait for space and place character in the output buffer for the
                 * lower half; Preserve the circular buffer */
                else
                {
                        wait(puart->osema);
                        puart->out[(puart->ostart + puart->ocount) % UART_OBLEN] = *buf++;
                        count++;
                        puart->ocount++;
                }
        }

        restore(ps);
        return count;
}

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