Re: USB: invalid maxpacket 8
From: Alan Stern
Date: Thu Nov 18 2021 - 12:27:42 EST
On Thu, Nov 18, 2021 at 10:04:03PM +0530, Muni Sekhar wrote:
> Hi all,
> I'm trying to connect to a USB device on Linux PC and getting an error
> about "invalid maxpacket 8". What does it mean?
It means that the kernel received two endpoint descriptors from the USB
device containing invalid values.
For devices communicating at High Speed (480 Mb/s) like yours, the
wMaxPacketSize field in the endpoint descriptor for a Bulk endpoint is
required to contain the value 512, but your device sent a couple of Bulk
endpoint descriptors in which wMaxPacketSize was set to 8. You will see
the invalid values if you look at the output from "lsusb -v" for the
> Does this error causes
> USB packet transfer failures?
This message is only a warning; the kernel will try to communicate with
the device regardless. But since that the device is obviously faulty,
the communication might not work.
> Any ideas how to fix this?
The only way to fix this is to change the device's firmware.
> Thank you for any pointers.
> dmesg log:
> [1920549.030669] usb 2-2: New USB device found, idVendor=05c6, idProduct=9500
> [1920549.030682] usb 2-2: New USB device strings: Mfr=0, Product=0,
> [1920549.032623] hub 2-2:1.0: USB hub found
> [1920549.032672] hub 2-2:1.0: 7 ports detected
> [1920549.302875] usb 2-2.1: new high-speed USB device number 98 using xhci_hcd
> [1920549.391765] usb 2-2.1: config 1 interface 0 altsetting 0 bulk
> endpoint 0x81 has invalid maxpacket 8
> [1920549.391777] usb 2-2.1: config 1 interface 0 altsetting 0 bulk
> endpoint 0x2 has invalid maxpacket 8