From owner-freebsd-hackers@FreeBSD.ORG  Mon Jun 18 06:59:23 2007
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From: Christian Kandeler <christian.kandeler@hob.de>
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Date: Mon, 18 Jun 2007 08:59:15 +0200
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Subject: Re: Question about serial console code
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On Friday 15 June 2007 18:03, Marcel Moolenaar wrote:

> The loop is formed by the transmit interrupt of the UART.
> When UART_TRANSMIT() is called, the FIFO of the UART is
> written and transmission starts. Eventually the UART will
> raise a "transmission done" interrupt, which will trigger
> the next iteration.

I see. However:

> If the UART has no FIFO (in the 16550-sense), then sc_txfifosz
> is still 1. 

But where is this set? The ns8250_bus_probe() function returns early when it 
detects a FIFO-less device, leaving sc_txfifosz at its pre-initialized value 
(i.e. zero). And it doesn't seem to get set anywhere else, either.

Regards,
Christian Kandeler