[PATCH v2] USB: serial: simple: narrow OWON match to avoid breaking VDS1022

[Huang Wei]

A USB_DEVICE() match on VID:PID 0x5345:0x1234 was added to the
owon_device entry in drivers/usb/serial/usb-serial-simple.c by
commit 4cc01410e1c1 ("USB: serial: simple: add OWON HDS200 series
oscilloscope support"). OWON uses this VID:PID across multiple device
families (HDS, VDS, SDS, PDS), so the broad match makes the
owon_device driver also claim devices such as the VDS1022.

While the owon_device entry is equivalent to the generic usbserial
driver for kernel-space users, the VDS1022 is a headless scope that
is driven from userspace over libusb (e.g. the florentbr/Owon-VDS1022
tool), which can no longer claim the interface once a kernel driver
binds to it. Prior to that commit, no in-kernel driver claimed these
interfaces.

The two families can be told apart by their interface descriptors
despite sharing interface class 5 (Physical): the HDS200 series
reports subclass 0 and protocol 0, as documented by the HDS272S dump
(firmware V5.7.1) in that commit's message, while the VDS1022 reports
subclass 6 and protocol 0x50. Match the full HDS200 interface
tuple so that the VDS1022 remains unclaimed and stays accessible to
userspace tools.

Reported-by: leStoppe <lestoppe@xxxxxxxxx>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220193
Tested-by: leStoppe <lestoppe@xxxxxxxxx>
Signed-off-by: Huang Wei <huangwei@xxxxxxxxxx>

---
Changes in v2:
- Rework the commit message per Johan Hovold's review: describe the
  libusb-based userspace breakage instead of the incorrect claim
  about falling back to the generic usbserial driver.
- Match on the full HDS200 interface tuple (subclass 0, protocol 0)
  instead of the interface class alone: both the HDS200 and the
  VDS1022 are interface class 5, so a class-only match would still
  claim the VDS1022. The tuple values are verified against the
  HDS272S dump in the commit message of 4cc01410e1c1 and the VDS1022
  dump provided by leStoppe.
- Fix the multi-line comment style.
---
 drivers/usb/serial/usb-serial-simple.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/usb-serial-simple.c b/drivers/usb/serial/usb-serial-simple.c
index a0afaf254d12..879508f54d69 100644
--- a/drivers/usb/serial/usb-serial-simple.c
+++ b/drivers/usb/serial/usb-serial-simple.c
@@ -100,9 +100,17 @@ DEVICE(nokia, NOKIA_IDS);
 	{ USB_DEVICE(0x09d7, 0x0100) }	/* NovAtel FlexPack GPS */
 DEVICE_N(novatel_gps, NOVATEL_IDS, 3);
 
-/* OWON electronic test and measurement equipment driver */
+/*
+ * OWON electronic test and measurement equipment driver.
+ * OWON uses the same VID:PID (0x5345:0x1234) for multiple device
+ * families (HDS, VDS, SDS, PDS). Match the full interface tuple
+ * reported by the HDS200 series (class 5, subclass 0, protocol 0) so
+ * that devices with a different interface tuple, such as the VDS1022
+ * (class 5, subclass 6, protocol 0x50) which is driven from userspace
+ * over libusb, remain unclaimed.
+ */
 #define OWON_IDS()			\
-	{ USB_DEVICE(0x5345, 0x1234) } /* HDS200 oscilloscopes and others */
+	{ USB_DEVICE_AND_INTERFACE_INFO(0x5345, 0x1234, 0x05, 0x00, 0x00) }
 DEVICE(owon, OWON_IDS);
 
 /* Siemens USB/MPI adapter */
-- 
2.25.1