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
