How do you keep input from a USB Mag card reader from going to STDIN?

How do you keep input from a USB Mag card reader from going to STDIN?

[Mark Butsch]

Hello,

I hope this is the correct place to post this.

I have both a USB keyboard and a USB Mag card reader (that works like a USB keyboard) connected to my system.

I would like to make it so the real keyboard is the only device that feeds STDIN and the mag card reader is only readable by reading that device directly.

If I "cat /proc/bus/input/devices" it shows:

I: Bus=0003 Vendor=04da Product=117c Version=0001
N: Name="Panasonic Panasonic USB keyboard compliant Mag-CR"
P: Phys=usb-0000:00:1d.3-1/input0
S: Sysfs=/class/input/input37
H: Handlers=kbd event5
B: EV=120003
B: KEY=10000 7 ff80007a 7ff febeffdf ffefffff ffffffff fffffffe
B: LED=1f

I: Bus=0003 Vendor=413c Product=2105 Version=0352
N: Name="Dell Dell USB Keyboard"
P: Phys=usb-0000:00:1d.0-1/input0
S: Sysfs=/class/input/input38
H: Handlers=kbd event2
B: EV=120003
B: KEY=10000 7 ff87207a c14057ff febeffdf ffefffff ffffffff fffffffe
B: LED=7

How would I disconnect the "kbd" handler from the mag card reader (and the mag card reader from the "kbd" handler) or is that the wrong approach?

Thanks in advance.

Mark Butsch

Re: How do you keep input from a USB Mag card reader from going to STDIN?

[Jiri Kosina]

On Wed, 10 Jun 2009, Mark Butsch wrote:

> I would like to make it so the real keyboard is the only device that 
> feeds STDIN and the mag card reader is only readable by reading that 
> device directly.
> 
> If I "cat /proc/bus/input/devices" it shows:
> 
> I: Bus=0003 Vendor=04da Product=117c Version=0001
> N: Name="Panasonic Panasonic USB keyboard compliant Mag-CR"
> P: Phys=usb-0000:00:1d.3-1/input0
> S: Sysfs=/class/input/input37
> H: Handlers=kbd event5
> B: EV=120003
> B: KEY=10000 7 ff80007a 7ff febeffdf ffefffff ffffffff fffffffe
> B: LED=1f
> 
> I: Bus=0003 Vendor=413c Product=2105 Version=0352
> N: Name="Dell Dell USB Keyboard"
> P: Phys=usb-0000:00:1d.0-1/input0
> S: Sysfs=/class/input/input38
> H: Handlers=kbd event2
> B: EV=120003
> B: KEY=10000 7 ff87207a c14057ff febeffdf ffefffff ffffffff fffffffe
> B: LED=7
> 
> How would I disconnect the "kbd" handler from the mag card reader (and 
> the mag card reader from the "kbd" handler) or is that the wrong 
> approach?

You can either unbind HID driver from the device completely, and write 
your own userspace driver using libusb.

Or you can patch the HID driver not to attach this device to inpu 
subsystem, and only trigger creation of /dev/hidraw (or /dev/hiddev 
respectively), and write user-space application that will process the HID 
events from these device nodes, and process them in your application as 
needed.

-- 
Jiri Kosina
SUSE Labs

Re: How do you keep input from a USB Mag card reader from going to STDIN?

[Janusz Krzysztofik]

Jiri Kosina wrote:
> On Wed, 10 Jun 2009, Mark Butsch wrote:
>> How would I disconnect the "kbd" handler from the mag card reader (and 
>> the mag card reader from the "kbd" handler) or is that the wrong 
>> approach?
> 
> You can either unbind HID driver from the device completely, and write 
> your own userspace driver using libusb.
> 
> Or you can patch the HID driver not to attach this device to inpu 
> subsystem, and only trigger creation of /dev/hidraw (or /dev/hiddev 
> respectively), and write user-space application that will process the HID 
> events from these device nodes, and process them in your application as 
> needed.

I thouhgt this could be done from userspace without any kernel 
modification, just the way "input-events -g" does it. Am I missing anything?

Janusz

Re: How do you keep input from a USB Mag card reader from going to STDIN?

[Jiri Kosina]

On Tue, 23 Jun 2009, Janusz Krzysztofik wrote:

> > You can either unbind HID driver from the device completely, and write your
> > own userspace driver using libusb.
> > Or you can patch the HID driver not to attach this device to inpu subsystem,
> > and only trigger creation of /dev/hidraw (or /dev/hiddev respectively), and
> > write user-space application that will process the HID events from these
> > device nodes, and process them in your application as needed.
> I thouhgt this could be done from userspace without any kernel modification,
> just the way "input-events -g" does it. Am I missing anything?

Calling ioctl(EVIOCGRAB) is of course another possibility, if you are 
perfectly fine with the work HID driver does and don't need any 
modifications there (i.e. no changes in usage parsing, etc).

-- 
Jiri Kosina
SUSE Labs