Date: Sun, 30 Nov 1997 19:56:41 +1100 From: Bruce Evans <bde@zeta.org.au> To: gurney_j@resnet.uoregon.edu, jak@cetlink.net Cc: bde@zeta.org.au, hackers@FreeBSD.ORG Subject: Re: 650 UART, SIO driver, 8259 PIC Message-ID: <199711300856.TAA05947@godzilla.zeta.org.au>
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>I've thought about upgrading sio so that it would understand the >existance of it, but there were a number of problems... the status >register is stored in the scratch register of the fourth port of the >board... also, on the AST/4 the port to write to, to clear ALL the >... >then you have to decide you to tell each port what it's number in the >status register... you don't want to have to force some aweful hack >like requiring the port number to be congruent to device number mod 4... >that would just be terrible (though most people do something similar).. Doesn't the master port give it? The master port is more for control, but it is a normal h/w hack for the control and status ports to be the same. >then to make matters worse... BOTH boards could possible be on the same >interrupt, and you have to check both port 4's scratch registers to see >who generated the port... >after all this came to light, I stopped work on it as there really was >no easy way to describe the different configurations in the flags of >the device... and this was even before Bruce used another bit to store >what one is the serial console... NetBSD uses a separate driver (with just the AST-specific parts). I'm not sure how it configures a pair of boards sharing an irq. BTW, flags hacks don't work well for multiple, not explicitly configurable units. E.g., we use the flags to configure individual wd drives, but there is no way to use them for inidividual sd drives. The console flag works for individual sio ports, but can't work for indiidual cy ports. Bruce
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