On Thu, 8 Mar 2007, Linos wrote:
> lsusb -v shows this for the Epson Printer:
>
> Bus 002 Device 003: ID 04b8:0202 Seiko Epson Corp. Receipt Printer M129C
...
> Interface Descriptor:
> bLength 9
> bDescriptorType 4
> bInterfaceNumber 0
> bAlternateSetting 0
> bNumEndpoints 2
> bInterfaceClass 255 Vendor Specific Class
> bInterfaceSubClass 255 Vendor Specific Subclass
> bInterfaceProtocol 2
Those values mean this printer uses a vendor-specific communication
protocol, not the standard USB printer protocol. As a result, usblp is
unwilling to drive it.
> ----------------------------------------------------------------------
>
> I have been able to do usblp recognize it changing this more lines in
> usblp.c.
>
>
> /* Analyze and pick initial alternate settings and endpoints. */
> protocol = usblp_select_alts(usblp);
> if (protocol < 0) {
> dbg("incompatible printer-class device 0x%4.4X/0x%4.4X",
> le16_to_cpu(dev->descriptor.idVendor),
> le16_to_cpu(dev->descriptor.idProduct));
> goto abort;
> }
>
> here i change "if (protocol < 0) {" for "if (protocol < -2000) {"
>
> ----------------------------------------------------------------------
>
> /* Setup the selected alternate setting and endpoints. */
> if (usblp_set_protocol(usblp, protocol) < 0)
> goto abort;
>
> here i change "(usblp_set_protocol(usblp, protocol) < 0)" for
> "(usblp_set_protocol(usblp, protocol) < -2000)"
>
> ----------------------------------------------------------------------
No, those are not the right changes to make.
I don't know if usblp will work with that printer at all. To find out,
you should remove these two lines near the top of usblp_select_alts():
if (ifd->desc.bInterfaceClass != 7 ||
ifd->desc.bInterfaceSubClass != 1)
continue;
> when i compile the module and install with insmod dmesg gives me this
> output.
>
> drivers/usb/class/usblp.c: usblp0: USB Unidirectional printer dev 3 if 0
> alt -1 proto 0 vid 0x04B8 pid 0x0202
> usbcore: registered new driver usblp
> drivers/usb/class/usblp.c: v0.13: USB Printer Device Class driver
>
>
> and i have the "/dev/usb/lp0" device but when i try to print anything.
>
>
> "echo test > /dev/usb/lp0" it fails and gives me this errors in dmesg:
>
> BUG: unable to handle kernel NULL pointer dereference at virtual address
> 00000000
...
> hehehe i would be better long away from kernel code i think :).
Probably. :-)
Try making the change above and see what happens.
Alan Stern
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