Shaun Jackman wrote:
The datasheet I have for the TL16C752B labels the MCR_OUT1 bit as
`FIFO Rdy enable' and the MCR_OUT2 bit as `IRQ enable'. The latter bit
concerns me. The 8250.c driver sets MCR_OUT2 by default; however, if
the user space clears MCR_OUT2 (through an ioctl TIOCMSET operation or
similar), it seems to me that interrupts for that UART will stop
working. Can someone confirm my suspicion?
I'd expect that clearing/setting the OUT1 and OUT2 pins from user
space should be an innocuous operation. Disabling interrupts is a
fairly nasty side effect.
The old 16550 OUT2 output (MCR:3) used to be a truly
independant control output that was commonly used
with an external gate to connect/disconnect the
interrupt request to the ISA bus.
Reading the TL16C752B datasheet, it seems pretty clear
that this gating is performed internal to the device.
MCR:3 is no longer an independant, general purpose I/O.
The result is the same though: If you dink around with
MCR:3 you could disable interrupts in either case.
So I don't see this as more or less of a problem than
other 16550 type devices.
--
Paul Fulghum
Microgate Systems, Ltd.
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