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[Bug 1891829] Re: High bit(s) sometimes set high on rcvd serial bytes wh
Launchpad Bug Tracker
[Bug 1891829] Re: High bit(s) sometimes set high on rcvd serial bytes when char size < 8 bits
Thu, 08 Jul 2021 04:17:18 -0000
[Expired for QEMU because there has been no activity for 60 days.]
** Changed in: qemu
Status: Incomplete => Expired
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High bit(s) sometimes set high on rcvd serial bytes when char size < 8
Status in QEMU:
I *believe* (not confirmed) that the old standard PC serial ports,
when configured with a character size of 7 bits or less, should set
non-data bits to 0 when the CPU reads received chars from the read
register. qemu doesn't do this.
Windows 1.01 will not make use of a serial mouse when bit 7 is 1. The
ID byte that the mouse sends on reset is ignored. I added a temporary
hack to set bit 7 to 0 on all incoming bytes, and this convinced
windows 1.01 to use the mouse.
note 1: This was using a real serial mouse through a passed-through
serial port. The emulated msmouse doesn't work for other reasons.
note 2: The USB serial port I am passing through to the guest sets
non-data bits to 1. Not sure if this is the USB hardware or linux.
note 3: I also needed to add an -icount line to slow down the guest
CPU, so that certain cpu-sensitive timing code in the guest didn't
give up too quickly.
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