Re: Device to write to all (serial) consoles
On 02.08.19 15:23, Paul Menzel wrote: Does a device exist, or can a device be configured so you can write to all (serial) consoles from user space? Why not just writing a little program that listens on a pipe or a pty and writes out everything to all the tty's you want ? --mtx -- Enrico Weigelt, metux IT consult Free software and Linux embedded engineering i...@metux.net -- +49-151-27565287
Re: Device to write to all (serial) consoles
On Sat, Aug 03, 2019 at 03:55:37PM +0200, Greg Kroah-Hartman wrote: > On Sat, Aug 03, 2019 at 03:23:23PM +0200, Adam Borowski wrote: > > On Fri, Aug 02, 2019 at 09:59:06PM +0200, Paul Menzel wrote: > > > Because the cable is always connected to the port on the back side, and > > > sometimes the port in the front has ID 0, and the one in the back 1, and > > > other times vice versa. We do not want to track that, and it would be > > > convenient to just write to both ports. > > > > Sounds like an XY problem then: what you want is not writing to all ports, > > but to have the port assignments stable (see also: disk device reordering). > > You can get that information from the symlinks in /dev/serial/ which > udev creates. Doesn't seem to work for me, for any ttyS0 ttyS1 ttySAC1 device: Box one, PCIe card + one USB dongle: 07:00.0 Serial controller: MosChip Semiconductor Technology Ltd. MCS9922 PCIe Multi-I/O Controller 07:00.1 Serial controller: MosChip Semiconductor Technology Ltd. MCS9922 PCIe Multi-I/O Controller Bus 003 Device 004: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter /dev/serial/by-id/usb-1a86_USB2.0-Serial-if00-port0 /dev/serial/by-path/pci-:0b:00.3-usb-0:4:1.0-port0 Only ttyUSB0 is there. Box two, on-board + one USB dongle: [3.404340] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled [3.431287] 00:01: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A Bus 001 Device 002: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP2102/CP2109 UART Bridge Controller [CP210x family] /dev/serial/by-id/usb-Silicon_Labs_CP2104_USB_to_UART_Bridge_Controller_00DB1604-if00-port0 /dev/serial/by-path/pci-:00:14.0-usb-0:1:1.0-port0 Box three: RockPro64, euler + USB dongle, kernel 4.4. Box four: Pine64, euler. Box five: Odroid-U2, something GPIOish (ttySAC1), kernel 5.0. Most are running kernel 5.2, Debian unstable. And indeed, in /lib/udev/rules.d/60-serial.rules : # /dev/serial/by-path/, /dev/serial/by-id/ for USB devices KERNEL!="ttyUSB[0-9]*|ttyACM[0-9]*", GOTO="serial_end" Like me, Paul is using ttyS0 for server-side. Meow! -- ⢀⣴⠾⠻⢶⣦⠀ ⣾⠁⢰⠒⠀⣿⡁ 10 people enter a bar: 1 who understands binary, ⢿⡄⠘⠷⠚⠋⠀ 1 who doesn't, D who prefer to write it as hex, ⠈⠳⣄ and 1 who narrowly avoided an off-by-one error.
Re: Device to write to all (serial) consoles
On Sat, Aug 03, 2019 at 03:23:23PM +0200, Adam Borowski wrote: > On Fri, Aug 02, 2019 at 09:59:06PM +0200, Paul Menzel wrote: > > On 02.08.19 18:02, Greg Kroah-Hartman wrote: > > > On Fri, Aug 02, 2019 at 03:23:08PM +0200, Paul Menzel wrote: > > > > On a lot of devices, like servers, you have more than one serial > > > > console, > > > > and you do not always know, how they are numbered. Therefore, we start a > > > > console on ttyS0 and ttyS1. > > > > Because the cable is always connected to the port on the back side, and > > sometimes the port in the front has ID 0, and the one in the back 1, and > > other times vice versa. We do not want to track that, and it would be > > convenient to just write to both ports. > > Sounds like an XY problem then: what you want is not writing to all ports, > but to have the port assignments stable (see also: disk device reordering). You can get that information from the symlinks in /dev/serial/ which udev creates.
Re: Device to write to all (serial) consoles
On Fri, Aug 02, 2019 at 09:59:06PM +0200, Paul Menzel wrote: > On 02.08.19 18:02, Greg Kroah-Hartman wrote: > > On Fri, Aug 02, 2019 at 03:23:08PM +0200, Paul Menzel wrote: > > > On a lot of devices, like servers, you have more than one serial console, > > > and you do not always know, how they are numbered. Therefore, we start a > > > console on ttyS0 and ttyS1. > > Because the cable is always connected to the port on the back side, and > sometimes the port in the front has ID 0, and the one in the back 1, and > other times vice versa. We do not want to track that, and it would be > convenient to just write to both ports. Sounds like an XY problem then: what you want is not writing to all ports, but to have the port assignments stable (see also: disk device reordering). Meow! -- ⢀⣴⠾⠻⢶⣦⠀ Latin: meow 4 characters, 4 columns, 4 bytes ⣾⠁⢠⠒⠀⣿⡁ Greek: μεου 4 characters, 4 columns, 8 bytes ⢿⡄⠘⠷⠚⠋ Runes: ᛗᛖᛟᚹ 4 characters, 4 columns, 12 bytes ⠈⠳⣄ Chinese: 喵 1 character, 2 columns, 3 bytes <-- best!
Re: Device to write to all (serial) consoles
On Fri, Aug 02, 2019 at 09:59:06PM +0200, Paul Menzel wrote: > Dear Greg, > > > On 02.08.19 18:02, Greg Kroah-Hartman wrote: > > On Fri, Aug 02, 2019 at 03:23:08PM +0200, Paul Menzel wrote: > > > > On a lot of devices, like servers, you have more than one serial console, > > > and you do not always know, how they are numbered. Therefore, we start a > > > console on ttyS0 and ttyS1. > > > > > > In user space, we also would like to write to both consoles to not worry > > > about the numbering. Writing to `/dev/console` only write to the active > > > console. > > > > So the same data to multiple console devices with just one userspace > > call? Why? > > Because the cable is always connected to the port on the back side, and > sometimes the port in the front has ID 0, and the one in the back 1, and > other times vice versa. We do not want to track that, and it would be > convenient to just write to both ports. > > > > $ more /proc/consoles # I think > > > tty0 -WU (EC p )4:1 > > > ttyS0-W- (E p a)4:65 > > > ttyS1-W- (E p a)4:65 > > > > > > Does a device exist, or can a device be configured so you can write to > > > all (serial) consoles from user space? > > > > With one syscall, not that I know of, sorry. > > Can such a device be created with udev or so? No, a single device node can not reference multiple device nodes at the same time, sorry. That's just not how they work at all. thanks, greg k-h
Re: Device to write to all (serial) consoles
Dear Greg, On 02.08.19 18:02, Greg Kroah-Hartman wrote: On Fri, Aug 02, 2019 at 03:23:08PM +0200, Paul Menzel wrote: On a lot of devices, like servers, you have more than one serial console, and you do not always know, how they are numbered. Therefore, we start a console on ttyS0 and ttyS1. In user space, we also would like to write to both consoles to not worry about the numbering. Writing to `/dev/console` only write to the active console. So the same data to multiple console devices with just one userspace call? Why? Because the cable is always connected to the port on the back side, and sometimes the port in the front has ID 0, and the one in the back 1, and other times vice versa. We do not want to track that, and it would be convenient to just write to both ports. $ more /proc/consoles # I think tty0 -WU (EC p )4:1 ttyS0-W- (E p a)4:65 ttyS1-W- (E p a)4:65 Does a device exist, or can a device be configured so you can write to all (serial) consoles from user space? With one syscall, not that I know of, sorry. Can such a device be created with udev or so? Kind regards, Paul
Re: Device to write to all (serial) consoles
On Fri, Aug 02, 2019 at 03:23:08PM +0200, Paul Menzel wrote: > Dear Linux folks, > > > On a lot of devices, like servers, you have more than one serial console, > and you do not always know, how they are numbered. Therefore, we start a > console on ttyS0 and ttyS1. > > In user space, we also would like to write to both consoles to not worry > about the numbering. Writing to `/dev/console` only write to the active > console. So the same data to multiple console devices with just one userspace call? Why? > $ more /proc/consoles # I think > tty0 -WU (EC p )4:1 > ttyS0-W- (E p a)4:65 > ttyS1-W- (E p a)4:65 > > Does a device exist, or can a device be configured so you can write to > all (serial) consoles from user space? With one syscall, not that I know of, sorry. greg k-h
Device to write to all (serial) consoles
Dear Linux folks, On a lot of devices, like servers, you have more than one serial console, and you do not always know, how they are numbered. Therefore, we start a console on ttyS0 and ttyS1. In user space, we also would like to write to both consoles to not worry about the numbering. Writing to `/dev/console` only write to the active console. $ more /proc/consoles # I think tty0 -WU (EC p )4:1 ttyS0-W- (E p a)4:65 ttyS1-W- (E p a)4:65 Does a device exist, or can a device be configured so you can write to all (serial) consoles from user space? Kind regards, Paul smime.p7s Description: S/MIME Cryptographic Signature
