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I have a nice little usb printer (Brother HL 5050). Since I don't print pages everyday, it's usually off (the computer OTOH is up 24h/24 7d/7 to do stuff like mail filtering). What I found much to my annoyance is the only way the system will recognize it is if it's up when the system boots, and never shut down afterwards. If it's not (as it's the case 9 times out of ten here) the only way to get printing working is to go into system-config-printer, edit the printer queue and click on rescan devices. You don't have to change the settings or whatever, just give a big kick in the butt of the printing subsystem so it notices the printer to which you've just sent jobs actually exists and (gosh) uses the device (/dev/usb/lp0) that was configured before. Can't the damn thing be smart enough to realise if we're printing the printer has probably been powered on, and it probably uses the same device as last time ? (ie do the rescan automatically whan it receives a new print job, and retry every 5s if it fails ?) This problem alone makes the system useless to small/home office setups - there is no way printing a new page should require a full system reboot to notice the printer and/or the root password.
I see kudzu fail to see a USB printer that it saw at install, even though it is powered on, too. Perhaps this is a kudzu or kernel problem.
This is most certainly not a kudzu problem. Kudzu is run at the computer startup time. A usb printer OTOH can be powered on/off at any time. And the kernel notices new usb devices just fine : Apr 4 15:27:45 rousalka kernel: usb 1-2: new high speed USB device using address 6 Apr 4 15:27:45 rousalka kernel: usb 1-2: Product: HL-5050 Apr 4 15:27:45 rousalka kernel: usb 1-2: Manufacturer: Brother Apr 4 15:27:45 rousalka kernel: usb 1-2: SerialNumber: A3J144655 Apr 4 15:27:45 rousalka kernel: drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 6 if 0 alt 0 proto 2 vid 0x04F9 pid 0x0017 Apr 4 15:27:45 rousalka usb.agent[25934]: ... no modules for USB product 4f9/17/100 Apr 4 15:27:47 rousalka udev[25968]: creating device node '/dev/lp0' If there is kernel/userspace actions to perform they belong in hotplug not kudzu. however the root of the problem is probably the printing subsystem scans the configured devices at startup, and considers their state can not change afterwards. This is plain false (even in parallel-land but with usb there is really no excuse not to notice a power on)
Just power-cycling the printer just after printing successfully a page results in : [nim@rousalka]~% lpq Babayaga is not ready Rank Owner Job File(s) Total Size 1st nim 115 (stdin) 40960 bytes Even though the kernel successfully followed the whole operation and notified userspace of it ehci_hcd 0000:00:10.3: GetStatus port 2 status 001002 POWER sig=se0 CSC hub 1-0:1.0: port 2, status 100, change 1, 12 Mb/s usb 1-2: USB disconnect, address 6 usb 1-2: usb_disable_device nuking all URBs usb 1-2: unregistering interface 1-2:1.0 drivers/usb/core/file.c: removing 0 minor drivers/usb/core/file.c: release_usb_class_dev - lp0 drivers/usb/class/usblp.c: usblp0: removed usb 1-2:1.0: hotplug usb 1-2: unregistering device usb 1-2: hotplug ehci_hcd 0000:00:10.3: GetStatus port 2 status 001803 POWER sig=j CSC CONNECT hub 1-0:1.0: port 2, status 501, change 1, 480 Mb/s hub 1-0:1.0: debounce: port 2: delay 100ms stable 4 status 0x501 ehci_hcd 0000:00:10.3: port 2 high speed ehci_hcd 0000:00:10.3: GetStatus port 2 status 001005 POWER sig=se0 PE CONNECT usb 1-2: new high speed USB device using address 7 usb 1-2: new device strings: Mfr=1, Product=2, SerialNumber=3 usb 1-2: default language 0x0409 usb 1-2: Product: HL-5050 usb 1-2: Manufacturer: Brother usb 1-2: SerialNumber: A3J144655 usb 1-2: hotplug usb 1-2: adding 1-2:1.0 (config #1, interface 0) usb 1-2:1.0: hotplug usblp 1-2:1.0: usb_probe_interface usblp 1-2:1.0: usb_probe_interface - got id drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 7 if 0 alt 0 proto 2 vid 0x04F9 pid 0x0017 drivers/usb/core/file.c: looking for a minor, starting at 0
The only workaround I know at this point to get the system notice the printer is once again available is to ask for a device rexcan manually as root in system-config-printer
How does one kick cups to tell it to rescan its available devices?
*** This bug has been marked as a duplicate of 81164 ***