On 09/01/2025 17:34, Alan Stern wrote: > On Thu, Jan 09, 2025 at 04:02:58PM +0200, Bitterblue Smith wrote: >> Hi, >> >> I have this wifi device with on-board storage for the Windows driver: >> >> New USB device found, idVendor=148f, idProduct=2878, bcdDevice= 0.01 >> >> After switching to wifi mode, we can see it's a MT7601U: >> >> New USB device found, idVendor=148f, idProduct=7601, bcdDevice= 0.00 >> >> The problem with this one is that it can't be mounted, nothing happens >> for a long time. I'm testing with kernel 6.12.8-arch1-1 but it's been >> like this for at least two years. >> >> The problem seems to be that reading from the "end" of the device >> takes 17 seconds. I assume the reason for that is the fake capacity: >> >> SCSI Payload (Read Capacity(10) Response Data) >> [LUN: 0x0000] >> [Command Set:CD-ROM (0x05) ] >> [MMC Opcode: Read Capacity(10) (0x25)] >> [Request in: 212] >> [Response in: 217] >> LBA: 65280 >> Block size in bytes: 2048 >> Read capacity: 133693440 bytes (127.50 MiB) >> >> The real capacity is probably just 8 MiB. The driver files stored in >> it are ~7 MiB total. >> >> This takes 17 seconds and returns 4096 bytes filled with 0xff: >> >> SCSI CDB Read(10) >> [LUN: 0x0000] >> [Command Set:CD-ROM (0x05) ] >> [Response in: 565] >> Opcode: Read(10) (0x28) >> Flags: 0x00 >> Logical Block Address (LBA): 0x0000fefc (65276) >> ...0 0000 = Group: 0x00 >> Transfer Length: 2 >> Control: 0x00 >> >> Windows never tries to read that far. (The device works in Windows.) >> >> How can this be fixed? > > Upgrade the WiFi device's firmware. If you can convince the vendor to > fix the bug, which seems unlikely because it works okay with Windows. > > Part of the partition probing (which tries to read the device's last > sector) is done by various userspace programs. But I think some of it > is also done by the kernel, and as far as I know the only way to prevent > it is to build a kernel without support for the partition schemes which > store some of their data near the end of the device. > > Probably your best approach is to tell usb-storage to ignore the device > completely. You can do this with a suitable module parameter for the > usb-storage driver. For example, add: > > usb-storage.quirks=148f:7601:i > > on the kernel's boot command line (or put a similar entry in an > /etc/modprobe.d/*.conf file if usb-storage is a loadable kernel module > on your system). Of course, then you wouldn't be able to mount the > device or access the Windows driver files on it, but I imagine you don't > care about them very much while you're running Linux. > >> usb_modeswitch can switch it to wifi mode, so it's not a huge problem. >> I'm just curious. > > If you really wanted, you could create a custom kernel which which > adjust the storage capacity of this particular device down to 8 MB. But > you would never be able to convince anyone to include such a workaround > in the main kernel. > > Alan Stern Haha, so it's hopeless. Thank you for the detailed explanation.
