Question regarding ns16550

[Sebastian Huber]

Hello Daniel,

I never notice a problem with this driver.  It should only write to the FIFO in 
case it is completely empty.  Did you observe problems?

On 21/10/14 19:32, Daniel Gutson wrote:
> Hi,
>
>     in the writing interrupt mode (ns16550_write_support_int), we have
>
>    for (i = 0; i < out; ++i) {
>      set( port, NS16550_TRANSMIT_BUFFER, buf [i]);
>    }
>
> Shouldn't we check, before writing to the register for the iterations
> after the first one,
> whether the character entered in the FIFO? (otherwise I think the
> 'for' loop could iterate
> so fast that the device had no time to process the character)
>
> In such a case, something like
>
>
>    for (i = 0; i < out; ++i) {
>
>     /* Wait for transmitter holding register to be empty */
>      do {
>        status = get( port, NS16550_LINE_STATUS);
>      } while ((status & SP_LSR_THOLD) == 0);
>
>      set( port, NS16550_TRANSMIT_BUFFER, buf [i]);
>    }
>
> would be better?
>
> Thanks,
>
>     Daniel.
>
>


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Sebastian Huber, embedded brains GmbH

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