Date: Wed, 10 Dec 2025 04:57:53 +0000 From: bugzilla-noreply@freebsd.org To: usb@FreeBSD.org Subject: [Bug 291506] libusb_open advisory lock (libusb compatiblity) Message-ID: <bug-291506-19105-BkULBbXL6v@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-291506-19105@https.bugs.freebsd.org/bugzilla/> References: <bug-291506-19105@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=291506 --- Comment #2 from unitrunker <unitrunker@unitrunker.net> --- == DRAFT (feedback welcome) == Requirements libusb_open assume: libusb_device parameter comes from libusb_get_device_list() succeeds on opening a valid, attached device not locked by any processes (including self). fails on opening a device locked by any process (including self). libusb_open_with_vid_pid for "N" valid, matching devices attached to host. succeeds on opening all N devices with matching vid/pid and not locked by any process (including self). fails when all valid, matching devices are taken by any process (including self). About "including self" - be sure to cover in-process testing where the same libusb_context is shared and also where a new libusb_context is created prior to each device open attempt. Tools Two USB devices with same VID/PID (preferrably with different serial numbers). usbgrab: a small test tool to take ownership of the first device with matching vid and pid on the host. Uses libusb_open_with_vid_pid. Synopis: usbgrab <vid> <pid> [-p] [-a] vid - four digit hexadecimal vendor id pid - four digit hexadecimal product id. -p pause, displays "Press enter..." and waits for input. Keeps the device "owned" for an indefinite amount of time. -a all - grabs all matching devices and displays how many were found. If -a is absent, the program grabs the first matching device. -p and -a may be combined. Test Plan A. Single device 1. Attach one device with known VID/PID. 2. run "usbgrab <vid> <pid> -p &" utility to take ownership of the device. 3. Verify the tool displays "Found: 1 Press enter ..." 4. run "usbgrab <vid> <pid>" in the foreground. 5. Verify an error is displayed. 6. run "fg" to place the earlier usbgrab process into the foreground. 7. press enter to exit the process. Verify no usbgrab background processes remain. B. Two devices, sequential 1. Attach two devices with same known VID/PID. 2. run "usbgrab <vid> <pid> -p &" utility to take ownership of the device. 3. Verify the tool displays "Found: 1 Press enter ..." 4. run "usbgrab <vid> <pid>" in the foreground. 5. Verify NO error is displayed. 6. run "fg" to place the earlier usbgrab process into the foreground. 7. press enter to exit the process. Verify no usbgrab background processes remain. C. Two devices, all or none 1. Attach two devices with same known VID/PID. 2. run "usbgrab <vid> <pid> -p -a &" utility to take ownership of all matching devices. 3. Verify the tool displays "Found: 2 Press enter ..." 4. run "usbgrab <vid> <pid>" in the foreground. 5. Verify an error is displayed. 6. run "fg" to place the earlier usbgrab process into the foreground. 7. press enter to exit the process. Verify no usbgrab background processes remain. D. Two devices, alternating 1. Attach two devices with same known VID/PID. 2. run "usbgrab <vid> <pid> -p &" utility to take ownership of the device and pause in the background. 3. Verify the tool displays "Found: 1 Press enter ..." 4. Make note of the background process pid. 5. run "usbgrab <vid> <pid> -p &" in the background to take ownership of the second device. 6. Verify "Found 1 Press enter ..." is displayed. 7. run "usbgrab <vid> <pid>" in the foreground. 8. Verify an error is displayed. 9. run "fg <pid>" to place the earlier usbgrab process into the foreground. 10. press enter to exit the process. 11. run "usbgrab <vid> <pid>" 12. Verify "Found 1" is displayed 13. run "fg" to place earlier usbgrab process into foreground. 14. press enter to exit the process. Verify no usbgrab background processes remain. Notes I tested this by running buildworld on a git clone of https://github.com/freebsd/freebsd-src.git Instead of installing the results, I renamed three files in /usr/lib (libusb.a, libusb.so, libusb.so.3) and copied the three newly built files into place. There's probably a better way but this works. Those scope of this change is so small - I can quickly deploy and roll-back the change to compare before vs. after behavior. Concerns For a USB device shared between kernel and userland, what impact might an advisory lock have on the libusb_detach_kernel_driver and libusb_attach_kernel_driver functions? The devices I use to test do not have kernel drivers. -- You are receiving this mail because: You are the assignee for the bug.
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