Hello I made some progress on this issue. The problem is common to NFC readers powered by the pn533 chip from NXP, which is quite common. It has at least two bugs in its USB implementation: - Large transfer can overwrite the chip USB configuration descriptors - In some situation the chip fails to update the toggle bit in USB frame.
The second problem causes ack frames from the chip to be silently discarded by the host controler. As a result, requests timeout without a reply. And when rebooting, the first problem causes NetBSD to reject the device attachement, because its USB configuration descriptors do not contain usable data. The only way to recover with our current kernel is to unplug/replug the device. libnfc has workarounds for the two problems. It uses the chip overflow on purpose to rewrite the correct USB descriptors, and it sends empty frames in order to get an ack with appropriate toggle bit when that problem happens. But that workarounds will only be of some help if middleware does not come in their ways. I found three situations where the NetBSD kernel USB implementation would break the day. Here are the proposed patches to fix the situation: 1) Provide fake USB descriptors https://ftp.espci.fr/shadow/manu/desc_fake.patch When we detect the USB descriptors are corrupted (type and size make no sense), we provide hard-coded configuration, interface and endpoint descriptors. We trigger that on appropriate USB product ID and vendor ID from the USB device descriptor, which fortunately is not corrupted. It works well for the pn533, because according to the chip documentation, the descriptors are immutable, hence our fake version is always right. This lets NetBSD configure the device on reboot after it has corrupted its USB descriptors, and libnfc can then actually use it. 2) Use USB timeout for ugen write operations https://ftp.espci.fr/shadow/manu/ugen_timeout.patch The ioctl USB_SET_TIMEOUT was only used for read operations in ugen(4). That patch makes sure it is also used for write operation, so that a user process will not wait forever for a missing ack frame. 3) Use USB timeout in usbd_transfer() https://ftp.espci.fr/shadow/manu/usb_sync_xfer.patch Make sure the USB timeout is used when doing synchronous USB transfers. Here again the goal is to avoid getting stuck in the kernel forever because the ack frame was rejected by the host controler. -- Emmanuel Dreyfus m...@netbsd.org
