I think for the vendor and product ID, we probably want to use symbolic constants from sys/usb/usbdevs.h.  Unfortunately it doesn't seem like we have a constant for that manufacturer right now, but we could add one, I think; e.g.,

diff --git a/usr/src/uts/common/io/usb/usbdevs b/usr/src/uts/common/io/usb/usbdevs
index 882e5168aa..fc89ee2da1 100644
--- a/usr/src/uts/common/io/usb/usbdevs
+++ b/usr/src/uts/common/io/usb/usbdevs
@@ -327,6 +327,7 @@ vendor GUNZE                0x0637  Gunze Electronics USA
 vendor AVISION         0x0638  Avision
 vendor TEAC            0x0644  TEAC
 vendor ACTON           0x0647  Acton Research Corp.
+vendor SIGMADESIGNS    0x0658  Sigma Designs, Inc.
 vendor OPTO            0x065a  Optoelectronics Co., Ltd
 vendor SGI             0x065e  Silicon Graphics
 vendor SANWASUPPLY     0x0663  Sanwa Supply
@@ -4262,6 +4263,9 @@ product SIERRA MC7430             0x9071  Sierra Wireless MC7430 Qualcomm Snapdragon X7 LTE-
 product SIERRA AC313U          0x68aa  Sierra Wireless AirCard 313U
 product SIERRA TRUINSTALL      0x0fff  Aircard Tru Installer

+/* Sigma Designs, Inc. products */
+product SIGMADESIGNS           0x0200  Aeotec Z-Stick Gen5 (ZW090) - UZB
+
 /* Sigmatel products */
 product SIGMATEL WBT_3052      0x4200  WBT-3052 IrDA/USB Bridge
 product SIGMATEL I_BEAD100     0x8008  i-Bead 100 MP3 Player

It looks like this continuation line is not quite right -- the last indent there should be four spaces, not a tab.

Apart from the comment text nits, this seems fine to me.

It'd be good to consistently capitalise "USB" and "ACM" in this comment.

To avoid the wrapping here, it'd be fine to give dev_descr a shorter name; e.g., dd.

Ship It!

Ship It!