| N. Albert via plug on 15 Jan 2025 05:28:04 -0800 |
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| Re: [PLUG] Parallel port with Debian 12 |
On 1/14/2025 7:57 AM, Rich Freeman wrote:
On Mon, Jan 13, 2025 at 8:55 PM N. Albert via plug <plug@lists.phillylinux.org> wrote:On 1/13/2025 8:36 PM, Michael Lazin via plug wrote:I don't think you can write to the parallel port with bash directly.Hmm, from some research I did initially, it seemed like it should be possibleSo, it has been eons since I've used this sort of hardware on linux, but I suspect it depends on your printer. Really old printers probably would just accept ascii text they receive and print it, unless preceded by escape codes and such. More modern printers may not still have this sort of legacy compatibility and may expect everything to be encoded in some sort of command language. Granted, if the printer actually HAS a parallel port it is probably for legacy purposes, but if it is just really old it might just be from the days when everything used Windows but USB wasn't ubiquitous. Bottom line is that it might depend. If you've been able to print this way on this particular printer in the past though I'd say it seems likely to work. I'm also not sure if CUPS can create a device node and then just translate via the printer driver.
Yup, that's how I'm printing to it under Windows. I'm not using any drivers either. I did look at the programmer's manual for it at the time (it's a Star Micronics TSP600 Thermal Printer) and that indicated I should be able to write raw text directly to the printer (there are also some special codes that can be used, which I don't need). When I send a job using smbclient, I can use raw text / newlines to format it the way I want (not that there is much formatting control). All my jobs are a single line at a time anyways.
I realize it can be made with CUPS but I don't need any of its features, it doesn't have the best security reputation of late, and I wanted to be able to write directly to the device file from the shell or the address in a C program. It would be like using a web browser when I just need netcat.
As far as your specific issue I can think of a few things that could go wrong, but that would be getting really into the weeds and I haven't dealt with a parallel printer in decades so I'm not sure you'd benefit from a lot of speculation. Questions that come to mind are whether the kernel driver is enabled, and whether the udev rule is sticking a device node where you think it ought to.the ability to write raw bytes directly to the ... device address (e.g. 0x378)That isn't something done trivially. First, it is normally the role of a kernel module and you'd need to run as root to use instructions like OUT.
I tried everything as root, so permissions definitely weren't the issue.
Second, that IO address isn't the printer - it is probably just a base address of a series of addresses that control the parallel port at a low level and actually sending data to it probably requires a bunch of initialization/etc.
I omitted it in my example, but I was also calling ioperm before like most of the examples have. I dug around and found the test program I cobbled together back then:
root@debian:/usr/src/pp# cat pp.c
#include <stdio.h>
#include <unistd.h>
#include <sys/io.h>
#define baseport 0x378
int main(int argc, char *argv[])
{
if (ioperm(baseport, 3, 1)) {
perror("ioperm");
return -1;
}
outb('t', baseport);
outb('e', baseport);
outb('s', baseport);
outb('\n', baseport);
return 0;
}
root@debian:/usr/src/pp# ./pp
root@debian:/usr/src/pp# echo $?
0
root@debian:/usr/src/pp#
A bit sloppy, this was just going to be a proof of concept, but it only
proved it wasn't working :(
Program runs successfully, but nothing happens. Similar experience when
redirecting text to the appropriate parallel port device file.
I'd have to go dig up the old docs on how those interfaces work. It isn't actually that hard (that sort of hardware is 1970s technology and very simple), but it isn't like you can just write a string in python to an IO port. Once initialized you probably could just loop through a string and send one byte at a time. Really though you should just figure out how to get the kernel to do its job.
Yup, that's kind of where I left of. I think both the C program and writing to the device file should work if the kernel has everything loaded right.
You might try running "udevadm info -t" and looking for parport somewhere in the output. That might give you some clues as to whether udev knows about the device and where it put the device node. Your kenrel seems to know about it from dmesg mentioning it, so I'm guessing it isn't a missing kernel driver, but again I haven't messed with those ports in ages so maybe I'm missing something there.
I definitely get a lot of stuff when doing that (and this is new for me, I hadn't tried it before). Output below.
I think there is definitely stuff loaded (maybe some of the drivers). My best guess is that *something* is missing, and I'm not quite sure what that is. I only say that because the lspci output I shared before was empty, and examples I found online showed it being non-empty.
root@debian:/usr/src/pp# udevadm info -t | cat | grep parport ├─/bus/parport │ ┆ P: /bus/parport │ ┆ M: parport │ ┆ E: DEVPATH=/bus/parport │ ┆ P: /bus/parport/drivers │ ┆ E: DEVPATH=/bus/parport/drivers │ │ ┆ P: /bus/parport/drivers/daisy_drv │ │ ┆ E: DEVPATH=/bus/parport/drivers/daisy_drv │ ┆ P: /bus/parport/drivers/ppdev │ ┆ E: DEVPATH=/bus/parport/drivers/ppdev │ ├─parport_pc │ │ ┆ P: /bus/platform/drivers/parport_pc │ │ ┆ M: parport_pc │ │ ┆ E: DEVPATH=/bus/platform/drivers/parport_pc ├─/devices/parport0 │ ┆ P: /devices/parport0 │ ┆ M: parport0 │ ┆ U: parport │ ┆ T: parport │ ┆ E: DEVPATH=/devices/parport0 │ ┆ E: SUBSYSTEM=parport │ ┆ E: DEVTYPE=parport ├─/devices/platform/parport_pc.888 │ ┆ P: /devices/platform/parport_pc.888 │ ┆ M: parport_pc.888 │ ┆ V: parport_pc │ ┆ E: DEVPATH=/devices/platform/parport_pc.888 │ ┆ E: DRIVER=parport_pc │ ┆ E: MODALIAS=platform:parport_pc │ ┆ E: ID_PATH=platform-parport_pc.888 │ ┆ E: ID_PATH_TAG=platform-parport_pc_888 │ └─ppdev/parport0 │ ┆ P: /devices/platform/parport_pc.888/ppdev/parport0 │ ┆ M: parport0 │ ┆ N: parport0 │ ┆ E: DEVPATH=/devices/platform/parport_pc.888/ppdev/parport0 │ ┆ E: DEVNAME=/dev/parport0 ├─/module/parport │ ┆ P: /module/parport │ ┆ M: parport │ ┆ E: DEVPATH=/module/parport ├─/module/parport_pc │ ┆ P: /module/parport_pc │ ┆ M: parport_pc │ ┆ E: DEVPATH=/module/parport_pc ___________________________________________________________________________ Philadelphia Linux Users Group -- http://www.phillylinux.org Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug