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--- faq [2020/02/26 20:47] – [What is the best wireless card to buy ?] updated AWUS036ACM mister_x
+++ faq [2021/06/08 01:38] (current) – My driver doesn't work anymore, or it does something weird, how to debug? mister_x
@@ Line 6: / Line 6: @@
 ===== What is the best wireless card to buy ?  =====
-Which card to purchase is a hard question to answer.  Each person's criteria is somewhat different, such as one may require 802.11n capability, or may require it to work via virtualization.  However, having said that, if money is not a constraint then the following cards are considered the best in class:
+Which card to purchase is a hard question to answer.  Each person's criteria is somewhat different, such as one may require 802.11ax capability, or may require it to work via virtualization.  However, having said that, then the following cards are considered the best in class:
   * Alfa AWUS036ACH (a/b/g/n/ac) is the best performing card, but the driver can be unstable enough to crash your kernel
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 This issue happens mostly in virtual machines, when the USB port is set to 3.0. To work around the issue, power off the virtual machine, edit USB settings of the VM and set it to 2.0.
+===== "xhci_hcd 0000:15:00.0: WARN Set TR Deq Ptr cmd failed due to incorrect slot or ep state" or similar in dmesg =====
+The following may be present in dmesg instead:
+  xhci_hcd 0000:00:14.0: WARN Cannot submit Set TR Deq Ptr
+  xhci_hcd 0000:00:14.0: A Set TR Deq Ptr command is pending.
+For mt76x0u, you may see any of the following messages as well:
+  mt76x0u 1-1:1.0: rx urb failed: -71
+  mt7601u 1-2:1.0: Error: mt7601u_mcu_wait_resp timed out
+  mt7601u 1-2:1.0: Vendor request req:07 off:0080 failed:-71
+  mt7601u: probe of 1-2:1.0 failed with error -110
+And for rt2800usb:
+  rt2x00usb_vendor_request: Error - Vendor Request 0x06 failed for offset 0x0404 with error -71
+  rt2800_wait_csr_ready: Error - Unstable hardware
+  rt2800usb_set_device_state: Error - Device failed to enter state 4 (-5)
+This [[https://bugzilla.kernel.org/show_bug.cgi?id=202541|bug]] affects kernels >= 4.20. It happens mostly when connecting certain USB 2.0 devices on a USB 3.0 port but it can happen with USB 3.0 devices as well. It isn't WiFi adapter's driver's fault, but an issue in the USB subsystem code.
+Until the bug is fixed, the workaround for USB 2.0 devices is to plug the device on a USB 2.0 port. If you are using a virtual machine, power off the virtual machine, and change USB port settings to 2.0.
 ===== Where can I find airmon-ng on Windows or MacOS? =====
 [[airmon-ng]] is a Linux/FreeBSD script only. There is no version for Windows, MacOS, or other OS at this time.
+===== My driver doesn't work anymore, or it does something weird, how to debug? =====
+We are assuming it used to work in the past, and that you have checked that network managers were killed prior to putting the card in monitor mode.
+The next step would be to look into 'dmesg' to see if the driver outputs any error or warnings.
+If the card is USB, clearing it using 'dmesg -c' before plugging the adapter may help, by decreasing the amount of messages you have to go through.