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7f477358e2
This patch implements a mode when a printer returns ENOSPC when it runs out of paper. The default remains the same as before. An application which wishes to use this function has to enable it explicitly with an ioctl LPABORT. This is done on a request by our (Fedora) CUPS guy, Tim Waugh. The API is similar enough to the lp0's one that CUPS works with both (but see below), but it's has some differences. Most importantly, the abort mode is persistent in case of lp0: once tunelp was run your cat fill blow up until you reboot or run tunelp again. For usblp, I made it so the abort mode is only in effect as long as device is open. This way you can mix and match CUPS and cat(1) freely and nothing bad happens even if you run out of paper. It is also safer in the face of any unexpected crashes. It has to be noted that mixing LPABORT and O_NONBLOCK is not advised. It probably does not do what you want: instead of returning -ENOSPC it will always return -EAGAIN (because it would otherwise block while waiting for the paper). Applications which use O_NONBLOCK should continue to use LPGETSTATUS like before. Finally, CUPS actually requires patching to take full advantage of this. It has several components; those which invoke LPABORT work, but some of them need the ioctl added. This is completely compatible, you can mix old CUPS and new kernels or vice versa. Signed-off-by: Pete Zaitcev <zaitcev@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
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| Kconfig | ||
| Makefile | ||
| README | ||
| usb-skeleton.c | ||
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("khubd").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.