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Enumerate more subsystems without libudev #238

Merged
merged 4 commits into from
Jan 10, 2025
Merged

Enumerate more subsystems without libudev #238

merged 4 commits into from
Jan 10, 2025

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sirhcel
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@sirhcel sirhcel commented Jan 4, 2025 •
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The serialport crate currently has two different port enumeration strategies on Linux: using libudev and manually scanning /sys/class/tty.

But there is a discrepancy between the ports returned. For example, the serial ports from a PCI card are not enumerated by the latter. Ports returned with the libudev enumeration on this machine:

$ cargo run --target x86_64-unknown-linux-gnu --features usbportinfo-interface --example list_ports
[...]
Found 7 ports:
    /dev/ttyS0
        Type: Unknown
    /dev/ttyS4
        Type: PCI
    /dev/ttyS5
        Type: PCI
    /dev/ttyUSB2
        Type: USB
        VID: 0403
        PID: 6001
        Interface: 00
        Serial Number: FTFOO
        Manufacturer: FTDI
        Product: UT232R
    /dev/ttyUSB3
[...]

And the ports returned without:

$ cargo run --target x86_64-unknown-linux-musl --no-default-features --features usbportinfo-interface --example list_ports
[...]
Found 5 ports:
    /dev/ttyS0
        Type: Unknown
    /dev/ttyUSB2
        Type: USB
        VID: 0403
        PID: 6001
        Interface: 00
        Serial Number: FTFOO
        Manufacturer: FTDI
        Product: UT232R
    /dev/ttyUSB3
[...]

This PR sets out to close this gap by using the device subsystem as criterion whether to report a certain device or not. Previously, presence and contents of the driver_override file in the sysfs tree was used but this excluded PCI devices as well as the UARTs of Raspberry Pi devices.

Enumeration of ports without libudev with the changes from this PR:

$ cargo run --target x86_64-unknown-linux-musl --no-default-features --features usbportinfo-interface --example list_ports
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.02s
     Running `target/x86_64-unknown-linux-musl/debug/examples/list_ports`
Found 7 ports:
    /dev/ttyS0
        Type: Unknown
    /dev/ttyS4
        Type: PCI
    /dev/ttyS5
        Type: PCI
    /dev/ttyUSB2
        Type: USB
        VID: 0403
        PID: 6001
        Interface: 00
        Serial Number: FTFOO
        Manufacturer: FTDI
        Product: UT232R
    /dev/ttyUSB3
[...]

There might be corner cases still not caught by this PR. But it improves the enumeration results for cases which knowingly failed beforehand.

sirhcel added 2 commits January 3, 2025 22:46
@sirhcel
Detect PCI devices too when using sysfs
02a90db 
The PCI serial ports I have at hand have been rejected previously by the
driver_override criterion: having the file present and its contents
being '(null)'.

Looking at the subsystem instead allows us to tell "actually existing"
serial ports apart from other TTYs which are not actual serial devices.
@sirhcel
Detect UARTs of Broadcom SoCs when using sysfs
72b4013 
For these UARTs the driver_overrive file containing '(null)' is also
present and the previous filtering would have ignored them as well.
@sirhcel sirhcel mentioned this pull request Jan 4, 2025
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@sirhcel sirhcel marked this pull request as ready for review January 9, 2025 21:50
@sirhcel sirhcel requested a review from eldruin January 9, 2025 21:50
@sirhcel sirhcel mentioned this pull request Jan 9, 2025
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eldruin
eldruin approved these changes Jan 10, 2025
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Looks good to me. Thank you for your work!

@eldruin eldruin merged commit b56fd25 into serialport:main Jan 10, 2025
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@sirhcel @eldruin