I tested every IP KVM in my Homelab

Re:I tested every IP KVM in my Homelab by JdeBP on Friday June 05, 2026 @03:42PM (#48417201)

I'm not from GL. I write my own USB HID handlers and I'm being nosy about bad protocol that exists in the wild. Was the 0 byte in some input report? In a descriptor? Somewhere else?

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Re:I tested every IP KVM in my Homelab by gregsadetsky on Friday June 05, 2026 @05:00PM (#48418210)

TLDR - GLKVM's kernel emits a trailing 0-byte DATA packet (ZLP) (which PiKVM does not)

Supposedly, this is due to the `req->zero = ((count % maxpacket) == 0)` line in the kernel's f_hid.c - which, for 8-byte HID keyboard reports, makes it append a trailer packet. Strict BIOS HID stacks treat this 0-byte packet as malformed and beep.

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Re:I tested every IP KVM in my Homelab by JdeBP on Friday June 05, 2026 @07:51PM (#48419889)

Interesting. My first thought is wondering whether the keyboard HID is adding report IDs to its input reports, because it isn't in boot mode or something. That would have that effect.

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Re:I tested every IP KVM in my Homelab by trumpdong on Sunday June 07, 2026 @08:21AM (#48434098)

Isn't that expected in USB so the receiving side knows it's at the end of the data transfer?

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