* [PATCH v4 1/2] usb: core: Add quirk for 255-bytes initial config read
2026-07-27 19:54 [PATCH v4 0/2] usb: core: Add quirk for 255-byte initial config read Nikhil Solanke
@ 2026-07-27 19:54 ` Nikhil Solanke
2026-07-27 19:54 ` [PATCH v4 2/2] usb: hub: Split announce_device() to log device identity before enumeration Nikhil Solanke
1 sibling, 0 replies; 3+ messages in thread
From: Nikhil Solanke @ 2026-07-27 19:54 UTC (permalink / raw)
To: linux-usb
Cc: gregkh, linux-kernel, stern, michal.pecio, corbet, skhan, stable,
linux-doc, Nikhil Solanke
Certain third-party USB game controllers exposing (or spoofing) an Xbox
360-compatible interface (VID:PID 045e:028e) fail to enumerate under Linux.
The device disconnects from the bus without responding to the initial
GET_DESCRIPTOR(CONFIGURATION) request, and the kernel logs 'unable to read
config index 0 descriptor/start: -71'.
The device then falls back to a secondary Android HID mode (with a
different VID:PID), losing XInput functionality including rumble support.
The failure reproduces across multiple machines, host controller types, and
kernel versions including current mainline and LTS. The device enumerates
correctly and remains in XInput mode under Windows. Notably, the device
enumerates correctly in Android mode when the same 9-byte request
is issued for that mode's configuration descriptor, confirming the firmware
bug is specific to the XInput mode.
usbmon traces from Linux and Wireshark/USBPcap traces from Windows are
identical up to the point of failure, with no visible protocol-level
difference explaining the divergence. The root cause was identified when
Michal Pecio discovered via a QEMU bus-level capture that Windows does not
use wLength=9 for the initial config descriptor request; it uses
wLength=255. Alan Stern subsequently confirmed this with a bus
analyzer on a different USB 2.0 device, and Michal verified the behavior
goes back to Windows 95 OSR2.1.
So, add a new quirk flag USB_QUIRK_WINDOWS_CONFIG_REQ_SIZE which causes
usb_get_configuration() to issue a 255 byte sized configuration request
instead of USB_DT_CONFIG_SIZE (9) for the initial
GET_DESCRIPTOR(CONFIGURATION) request, mimicking long-standing Windows
behavior.
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Suggested-by: Michal Pecio <michal.pecio@gmail.com>
Closes: https://lore.kernel.org/linux-usb/CAFgddh+JWdT4LLwMc5qjM8q_pBu-fRo2qADR5ovAKoGHWMQrRw@mail.gmail.com/
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Nikhil Solanke <nikhilsolanke5@gmail.com>
---
Changes in v4:
- Reworded comments and messages
- Moved the memcpy() block that skips the second read after USB_QUIRK_DELAY_INIT
.../admin-guide/kernel-parameters.txt | 5 +++
drivers/usb/core/config.c | 32 ++++++++++++++-----
drivers/usb/core/quirks.c | 4 +++
include/linux/usb/quirks.h | 3 ++
4 files changed, 36 insertions(+), 8 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index b5493a7f8f22..3d35270dddef 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -8169,6 +8169,11 @@ Kernel parameters
q = USB_QUIRK_FORCE_ONE_CONFIG (Device
claims zero configurations,
forcing to 1);
+ r = USB_QUIRK_WINDOWS_CONFIG_REQ_SIZE (Device
+ fails during initialization when asked for
+ 9-bytes configuration descriptor request.
+ Ask for 255-bytes request instead to mirror
+ Windows' behavior);
Example: quirks=0781:5580:bk,0a5c:5834:gij
usbhid.mousepoll=
diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 45e20c6d76c0..346a2faa9bb8 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -912,6 +912,18 @@ int usb_get_configuration(struct usb_device *dev)
unsigned char *bigbuffer;
struct usb_config_descriptor *desc;
int result;
+ size_t usb_config_req_size;
+
+ /*
+ * We usually start by grabbing the first 9-bytes descriptor so we know
+ * how long the whole configuration is. Some devices with quirky
+ * firmware will fail enumeration, so if the quirk is set, use 255 instead,
+ * mirroring the behavior of Windows.
+ */
+ if (dev->quirks & USB_QUIRK_WINDOWS_CONFIG_REQ_SIZE)
+ usb_config_req_size = 255;
+ else
+ usb_config_req_size = USB_DT_CONFIG_SIZE;
if (ncfg > USB_MAXCONFIG) {
dev_notice(ddev, "too many configurations: %d, "
@@ -938,15 +950,13 @@ int usb_get_configuration(struct usb_device *dev)
if (!dev->rawdescriptors)
return -ENOMEM;
- desc = kmalloc(USB_DT_CONFIG_SIZE, GFP_KERNEL);
+ desc = kmalloc(usb_config_req_size, GFP_KERNEL);
if (!desc)
return -ENOMEM;
for (cfgno = 0; cfgno < ncfg; cfgno++) {
- /* We grab just the first descriptor so we know how long
- * the whole configuration is */
result = usb_get_descriptor(dev, USB_DT_CONFIG, cfgno,
- desc, USB_DT_CONFIG_SIZE);
+ desc, usb_config_req_size);
if (result < 0) {
dev_err(ddev, "unable to read config index %d "
"descriptor/%s: %d\n", cfgno, "start", result);
@@ -956,16 +966,14 @@ int usb_get_configuration(struct usb_device *dev)
dev->descriptor.bNumConfigurations = cfgno;
break;
} else if (result < 4) {
- dev_err(ddev, "config index %d descriptor too short "
- "(expected %i, got %i)\n", cfgno,
- USB_DT_CONFIG_SIZE, result);
+ dev_err(ddev, "config index %d descriptor too short (asked for %zu, got %i)\n",
+ cfgno, usb_config_req_size, result);
result = -EINVAL;
goto err;
}
length = max_t(int, le16_to_cpu(desc->wTotalLength),
USB_DT_CONFIG_SIZE);
- /* Now that we know the length, get the whole thing */
bigbuffer = kmalloc(length, GFP_KERNEL);
if (!bigbuffer) {
result = -ENOMEM;
@@ -975,6 +983,13 @@ int usb_get_configuration(struct usb_device *dev)
if (dev->quirks & USB_QUIRK_DELAY_INIT)
msleep(200);
+ /* Skip the second read if we already got everything */
+ if (result >= length) {
+ memcpy(bigbuffer, desc, length);
+ goto store_and_parse;
+ }
+
+ /* Get the whole thing */
result = usb_get_descriptor(dev, USB_DT_CONFIG, cfgno,
bigbuffer, length);
if (result < 0) {
@@ -989,6 +1004,7 @@ int usb_get_configuration(struct usb_device *dev)
length = result;
}
+store_and_parse:
dev->rawdescriptors[cfgno] = bigbuffer;
result = usb_parse_configuration(dev, cfgno,
diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
index 87ee2d938bc0..f5a60ccf21d3 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -142,6 +142,10 @@ static int quirks_param_set(const char *value, const struct kernel_param *kp)
break;
case 'q':
flags |= USB_QUIRK_FORCE_ONE_CONFIG;
+ break;
+ case 'r':
+ flags |= USB_QUIRK_WINDOWS_CONFIG_REQ_SIZE;
+ break;
/* Ignore unrecognized flag characters */
}
}
diff --git a/include/linux/usb/quirks.h b/include/linux/usb/quirks.h
index b3cc7beab4a3..a4043b33c2c2 100644
--- a/include/linux/usb/quirks.h
+++ b/include/linux/usb/quirks.h
@@ -81,4 +81,7 @@
/* Device claims zero configurations, forcing to 1 */
#define USB_QUIRK_FORCE_ONE_CONFIG BIT(18)
+/* Use a 255 bytes config descriptor request mirroring windows behavior */
+#define USB_QUIRK_WINDOWS_CONFIG_REQ_SIZE BIT(19)
+
#endif /* __LINUX_USB_QUIRKS_H */
--
2.54.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v4 2/2] usb: hub: Split announce_device() to log device identity before enumeration
2026-07-27 19:54 [PATCH v4 0/2] usb: core: Add quirk for 255-byte initial config read Nikhil Solanke
2026-07-27 19:54 ` [PATCH v4 1/2] usb: core: Add quirk for 255-bytes " Nikhil Solanke
@ 2026-07-27 19:54 ` Nikhil Solanke
1 sibling, 0 replies; 3+ messages in thread
From: Nikhil Solanke @ 2026-07-27 19:54 UTC (permalink / raw)
To: linux-usb
Cc: gregkh, linux-kernel, stern, michal.pecio, corbet, skhan, stable,
linux-doc, Nikhil Solanke
announce_device() currently logs the device VID:PID and string
descriptors only after successful enumeration. This means that if
enumeration fails, no identifying information about the device appears
in the kernel log, making it difficult to diagnose failures.
Split announce_device() into announce_device_ids(), which logs the
VID:PID and bcdDevice immediately after the device descriptor is read,
and announce_device_strings(), which logs the product, manufacturer,
and serial number strings after successful enumeration. This ensures
that a device's identity is always visible in the log regardless of
whether enumeration succeeds or fails.
Suggested-by: Michal Pecio <michal.pecio@gmail.com>
Signed-off-by: Nikhil Solanke <nikhilsolanke5@gmail.com>
---
drivers/usb/core/hub.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 5262e11c12cd..d92bf887739d 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2401,7 +2401,7 @@ static void show_string(struct usb_device *udev, char *id, char *string)
dev_info(&udev->dev, "%s: %s\n", id, string);
}
-static void announce_device(struct usb_device *udev)
+static void announce_device_ids(struct usb_device *udev)
{
u16 bcdDevice = le16_to_cpu(udev->descriptor.bcdDevice);
@@ -2410,6 +2410,10 @@ static void announce_device(struct usb_device *udev)
le16_to_cpu(udev->descriptor.idVendor),
le16_to_cpu(udev->descriptor.idProduct),
bcdDevice >> 8, bcdDevice & 0xff);
+}
+
+static void announce_device_strings(struct usb_device *udev)
+{
dev_info(&udev->dev,
"New USB device strings: Mfr=%d, Product=%d, SerialNumber=%d\n",
udev->descriptor.iManufacturer,
@@ -2420,7 +2424,8 @@ static void announce_device(struct usb_device *udev)
show_string(udev, "SerialNumber", udev->serial);
}
#else
-static inline void announce_device(struct usb_device *udev) { }
+static inline void announce_device_ids(struct usb_device *udev) { }
+static inline void announce_device_strings(struct usb_device *udev) { }
#endif
@@ -2651,6 +2656,9 @@ int usb_new_device(struct usb_device *udev)
device_init_wakeup(&udev->dev, 0);
}
+ /* Announce the device identity */
+ announce_device_ids(udev);
+
/* Tell the runtime-PM framework the device is active */
pm_runtime_set_active(&udev->dev);
pm_runtime_get_noresume(&udev->dev);
@@ -2672,8 +2680,8 @@ int usb_new_device(struct usb_device *udev)
udev->dev.devt = MKDEV(USB_DEVICE_MAJOR,
(((udev->bus->busnum-1) * 128) + (udev->devnum-1)));
- /* Tell the world! */
- announce_device(udev);
+ /* Announce the device's product, manufacturer and serial number */
+ announce_device_strings(udev);
if (udev->serial)
add_device_randomness(udev->serial, strlen(udev->serial));
--
2.54.0
^ permalink raw reply related [flat|nested] 3+ messages in thread