On Tue, Jun 27, 2017 at 06:32:07PM -0600, Philip Prindeville wrote: > I’m running 3.10.0 (CentOS 7.3) on a Supermicro X10SDV-8C-TLN4F > motherboard, which has a 16550A on it. That's really old and obsolete, and not supported by the community at all. Care to use a more modern kernel? :) > What’s odd is that when I look in /dev/ I see ttyS0…S3, even though > there are only 2 hardware ports (a single DUART). > > [root@kvm2 logwatch]# setserial -G /dev/ttyS0 > /dev/ttyS0 uart 16550A port 0x03f8 irq 4 baud_base 115200 spd_normal skip_test > [root@kvm2 logwatch]# setserial -G /dev/ttyS1 > /dev/ttyS1 uart 16550A port 0x02f8 irq 3 baud_base 115200 spd_normal skip_test > [root@kvm2 logwatch]# setserial -G /dev/ttyS2 > /dev/ttyS2 uart unknown port 0x03e8 irq 4 baud_base 115200 spd_normal skip_test > [root@kvm2 logwatch]# setserial -G /dev/ttyS3 > /dev/ttyS3 uart unknown port 0x02e8 irq 3 baud_base 115200 spd_normal > > > and dmesg says: > > [ 3.173481] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled > [ 3.194077] 00:03: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A > [ 3.214710] 00:04: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A > > > I was trying to figure out where this happens, and why, so maybe I > could submit a patch to allow one to suppress this behavior (say with > “8250.only_real_hw=1” or some other module parameter). > > Not sure where this is happening. Thought it might be in > drivers/tty/serial/8250/8250_pnp.c but nothing stands out. > > Anyone know the backstory on why this happens, and how to > (conditionally) change this behavior? Why do you need to change this? What is wrong with the existing way this works? As for the code that implements it, it's the platform driver for your system that thinks the serial ports are there to remain compatible with the old PC standard. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
