linux - how to find out which ioports be assigned to my devices

Question

has linux reserved io port numbers for all manufactured devices.

I have devices like intel built-in network card. or another device I have for wifi (usb) from realtek. On linux repository on github, device drivers use specific io ports to register. And kernel assign those ports to device driver. device drivers normally request for ports using call to request_region function. so for some ethernet device it requests like following

    for (id_port = 0x110 ; id_port < 0x200; id_port += 0x10)
     {
    if (!request_region(id_port, 1, "3c509-control")) 
    continue;
    outb(0x00, id_port);
    outb(0xff, id_port);
    if (inb(id_port) & 0x01)
    break;
    else
    release_region(id_port, 1);
    }

above starts with 0x110 to 0x200, any port can be assigned in this range by kernel to driver and appear in /proc/ioports file means driver is using that io port by the time of success return from request_region.

Question : So my question is has linux assigned io ports to all manufactured devices usable with kernel 5.7 or latest kernel version?

Question : What if I want to write device driver for any device. How can I find the io ports number range to request to. I dont not expect that I have to look into kernel code and find similer driver port range. so How can I find that io port number range. how to achieve this first step required in writing device driver (any device. be it wifi internet device or ethernet device)

question from:https://stackoverflow.com/questions/65541049/how-to-find-out-which-ioports-be-assigned-to-my-devices

Answer 1

Question : So my question is has linux assigned io ports to all manufactured devices usable with kernel 5.7 or latest kernel version?

No.

Question : What if I want to write device driver for any device. How can I find the io ports number range to request to.

You ask the user for it. After all it's the user who set them using jumpers on the ISA card.

Here's a picture of an old Sound Blaster card (taken from Wikipedia, I'm too lazy to rummage around in my basement now). I've highlighted a specific area in the picture:

That jumper header I highlighted: That's the port configuration jumper. As a user you literally connect two of the pins with a jumper connector and that connects a specific address line that comes from the card connectors to the circuitry on the rest of the card. This address line is part of the AT bus port I/O scheme. The user sets this jumper, writes down the number and then tells the driver, which number it was set to. That's how AT style I/O ports.

Or the driver uses one of the well known port numbers for specific hardware (like network controllers) that dates back to the era, where ISA style ports were still are thing. Also there's old ISA-P'n'P where the BIOS and the add-in cards would negotiate the port assignments at power up, before the OS even started. You can read those port numbers with the ISA-P'n'P API provided by the kernel.

We no longer use this kind of hardware in practice! Except for legacy and retro computing purposes.

Over a quarter of century ago, the old AT / ISA bus was superseeded with PCI. Today we use PCIe which, from the point of view of software still looks like PCI. One of the important things about PCI was, that it completely dropped the whole concept of ports.

With ISA what you had were 8 data lines and 16 address lines, plus two read/write enable lines, one for memory mapped I/O and one for port I/O. You can find the details here https://archive.is/3jjZj. But what happens when you're reading from say, port 0x0104, it would physically set the bit pattern of 0x0104 to the address lines on the ISA bus, pull low the read enable line, and then read the voltage level on the data lines. And all of that is implemented as an actual set of instructions of the x86: https://c9x.me/x86/html/file_module_x86_id_139.html

Now look at the PCI bus: There's no longer separate data and address lines. Instead read/write commands would be sent, and everything happens through memory mappings. PCI devices have something called a BAR: a Base Address Register. This is configured by the PCI root complex and assigns the hardware the region of actual physical bus addresses where it appears. The OS has to get those BAR information from the PCI root complex. The driver uses the PCI IDs to have the hardware discovered and the BAR information told to it. It can then do memory reads/writes to talk to the hardware. No I/O ports involved. And that is just the lowest level. USB and Ethernet happen a lot further up. USB is quite abstract, as is Ethernet.

Your other question Looking for driver developer datasheet of Intel(R) Core(TM) i5-2450M CPU @ 2.50GHz suggests, that you have some serious misconceptions of what is actually going on. You were asking about USB devices, and Ethernet ports. Neither of those in any way directly interact with this part of the computer.

Your question per se is interesting. But we're also running into a massive XYZ problem here; it's worse than an XY problem; you're asking about X, although you want to solve Y. But Y isn't even the problem you're dealing with in the first place.

You're obviously smart, and curious, and I applaud that. But I have to tell you, that you've to backtrack quite a bit, to clear up some of the misconceptions you have.