Package: libsane Version: 1.0.25-2 Severity: normal Tags: patch Dear Maintainer,
I have a Canon Canoscan N650U. It uses the 'plustek' USB sane backend. When I upgraded my laptop, sane stopped working. sane_find_scanner would find my Canoscan, but scanimage -L would hang for a long time (maybe 20 seconds) and then fail, reporting no scanners found. If I ran scanimage -L again, it would fail immediately. If I unplugged and restored the USB cable, the first scenario occurred again. (xsane and the GIMP plugin also had the long pause, but would usually eventually show the device as detected. However, any attempt to access it caused an I/O error to be reported.) With SANE_DEBUG_SANEI_USB set, I could see that six bulk writes of 4 or 5 bytes each would succeed, but the seventh would return "Resource temporarily unavailable". However, the code did not catch the error, leading to many more failed writes, and hence the long delay. After much experimentation, (at first I thought it was the device going to sleep with autosuspend) I found a hack that would work: a delay before the call to libusb_bulk_write. Clearly, that's not a proper solution, but it's a workaround for me. I reduced the timeout gradually to 50 microseconds, but gave up reducing it at that point. A diff of my hack is as follows (against source of sane-backends-1.0.25): $ diff sanei_usb.c sanei_usb.c.orig 87,88d86 < < 2416,2419d2413 < struct timespec sleepytime, sleepyremain; < < sleepytime.tv_nsec = 50000L; /* nanoseconds */ < sleepytime.tv_sec = 0; 2450,2451d2443 < nanosleep(&sleepytime, &sleepyremain); /* sg */ < 2456c2448 < if (write_size <= 0) --- > if (write_size < 0) -- System Information: Debian Release: wheezy/sid APT prefers unstable APT policy: (500, 'unstable') Architecture: amd64 (x86_64) Foreign Architectures: i386 Kernel: Linux 4.4.0-fuji (SMP w/4 CPU cores; PREEMPT) Locale: LANG=en_IE.UTF-8, LC_CTYPE=en_IE.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_IE.UTF-8) Shell: /bin/sh linked to /bin/dash Init: sysvinit (via /sbin/init) Versions of packages libsane depends on: ii acl 2.2.51-8 ii adduser 3.113+nmu3 ii libavahi-client3 0.6.31-4 ii libavahi-common3 0.6.31-4 ii libc6 2.19-7 ii libexif12 0.6.21-1 ii libgphoto2-6 2.5.2-2 ii libgphoto2-port12 2.5.9-2 ii libieee1284-3 0.2.11-10 ii libjpeg62-turbo 1:1.3.1-10 ii libsane-common 1.0.25-2 ii libtiff5 4.0.3-5 ii libusb-1.0-0 2:1.0.20-1 ii makedev 2.3.1-93 ii udev 204-10 Versions of packages libsane recommends: pn libsane-extras <none> ii sane-utils 1.0.25-2 Versions of packages libsane suggests: pn avahi-daemon <none> pn hplip <none> -- no debconf information
