[SOLVED] Request: Support for more serial ports in the default kernels.
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Request: Support for more serial ports in the default kernels.
8250 serial driver supports more than 4 ports, and allows for a kernel parameter to request for more than the default number of ports, but there is a hard limit currently of 4 in Slackware's default kernels which means a kernel rebuild is required to go above 4.
Would it be possible to increase CONFIG_SERIAL_8250_NR_UARTS to 8 or even 16 in future kernels?
CONFIG_SERIAL_8250_RUNTIME_UARTS could stay as 4 (which limits the creation of additional ttys without a kernel parameter) to keep behaviour for the general public the same.
I don't think it is identical, but fair point to check upstream. Upstream default is indeed still 4.
I did a bit of searching around to find out what other distros.
(This information could be a year out of date)
ArchLinux has it set to 32 (with runtime as 32).
CentOS has it set to 64 (with runtime as 4).
Debian has it set to 32 (with runtime as 4).
Fedora has it set to 32 (with runtime as 32).
Oracle Server has it set to 32 (with runtime as 4).
Red Hat Enterprise has it set to 64 (with runtime as 4).
SuSE Enterprise has it set to 32 (with runtime as 32).
Ubuntu has it set to 48 (with runtime as 4 -> 32 in various kernel flavours).
Adding some context of the two options from the kernel here, to avoid needing to dig around.
Code:
config SERIAL_8250_NR_UARTS
int "Maximum number of 8250/16550 serial ports"
depends on SERIAL_8250
default "4"
help
Set this to the number of serial ports you want the driver
to support. This includes any ports discovered via ACPI or
PCI enumeration and any ports that may be added at run-time
via hot-plug, or any ISA multi-port serial cards.
config SERIAL_8250_RUNTIME_UARTS
int "Number of 8250/16550 serial ports to register at runtime"
depends on SERIAL_8250
range 0 SERIAL_8250_NR_UARTS
default "4"
help
Set this to the maximum number of serial ports you want
the kernel to register at boot time. This can be overridden
with the module parameter "nr_uarts", or boot-time parameter
8250.nr_uarts
kernel-source: kernel-source (Linux kernel source)
kernel-source:
kernel-source: Source code for Linus Torvalds' Linux kernel.
kernel-source:
kernel-source: This is the complete and unmodified source code for the Linux kernel.
The kernel in fact ships with defconfigs for different platforms as well (separately from the configs Slackware uses, which have evolved independently over time).
The defconfigs actually have CONFIG_SERIAL_8250_NR_UARTS set to 32 on i386/x86_64, so I think it would make sense to bump Slackware to that as well.
It was changed from 4 to 32 in May, 2008:
Code:
commit 5cb04df8d3f03e37a19f2502591a84156be71772
Author: Ingo Molnar <mingo@elte.hu>
Date: Sun May 4 19:49:04 2008 +0200
x86: defconfig updates
refresh 32-bit defconfig too, and update the 64-bit configs as well,
the defconfig should be much more useful by default, so most of the
updates are the enabling of various options.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Request: Support for more serial ports in the default kernels.
