Hi,
In hiddev.c (2.4.22 and 2.6.0-test6), setting the value with
HIDIOCSUSAGE triggers the following piece of code:
> case HIDIOCSUSAGE:
> field->value[uref.usage_index] = uref.value;
> return 0;
However, there may not be a one-to-one mapping between the
"Usage" list and the values list (controls).
http://www.usb.org/developers/devclass_docs/Hut1_11.pdf says
(page 40):
> While Local items do not carry over to the next Main item, they may
> apply to more than one control within a single item. For example, if
> an Input item defining five controls is preceded by three Usage
> tags, the three usages would be assigned sequentially to the first
> three controls, and the third usage would also be assigned to the
> fourth and fifth controls. If an item has no controls (Report Count
> = 0), the Local item tags apply to the Main item (usually a
> collection item).
> To assign unique usages to every control in a single Main item,
> simply specify
> each Usage tag sequentially (or use Usage Minimum or Usage Maximum).
> All Local items are unsigned integers.
It is likely to be the source of the problem reported
by Jackson Chan, last in June 2003
http://marc.theaimsgroup.com/?l=linux-usb-devel&m=105614111827576&w=2
Here is the lsusb -v output for the device I'm using.
HIDIOCSUSAGE will only let me access the first Output control. It
should assign the first Usage to the other controls, as suggested in
the HID document above.
----------------------------------------------------------------------
Bus 001 Device 005: ID 06c2:0052
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.10
bDeviceClass 0 Interface
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x06c2
idProduct 0x0052
bcdDevice 1.00
iManufacturer 1 Phidgets Inc.
iProduct 2 PhidgetTextLCD
iSerial 3 01559
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 34
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
MaxPower 64mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 3 Human Interface Devices
bInterfaceSubClass 0 No Subclass
bInterfaceProtocol 0 None
iInterface 0
HID Device Descriptor:
bLength 9
bDescriptorType 33
bcdHID 1.00
bCountryCode 0
bNumDescriptors 1
bDescriptorType 34 Report
wDescriptorLength 32
Report Descriptor: (length is 32)
Item(Global): Usage Page, data= [ 0xa0 0xff ] 65440
(null)
Item(Local ): Usage, data= [ 0x01 ] 1
(null)
Item(Main ): Collection, data= [ 0x01 ] 1
Application
Item(Local ): Usage, data= [ 0x02 ] 2
(null)
Item(Main ): Collection, data= [ 0x00 ] 0
Physical
Item(Global): Usage Page, data= [ 0xa1 0xff ] 65441
(null)
Item(Local ): Usage, data= [ 0x03 ] 3
(null)
Item(Global): Report Size, data= [ 0x08 ] 8
Item(Global): Report Count, data= [ 0x02 ] 2
Item(Main ): Input, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Local ): Usage, data= [ 0x04 ] 4
(null)
Item(Global): Report Size, data= [ 0x08 ] 8
Item(Global): Report Count, data= [ 0x08 ] 8
Item(Main ): Output, data= [ 0x02 ] 2
Data Variable Absolute No_Wrap Linear
Preferred_State No_Null_Position Non_Volatile Bitfield
Item(Main ): End Collection, data=none
Item(Main ): End Collection, data=none
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type none
wMaxPacketSize 8
bInterval 10
Language IDs: (length=4)
0409 English(US)
----------------------------------------------------------------------
If I misunderstood the rationale, I'd very much appreciate if
someone could tell me how to set the values without HIDIOCSUSAGE.
Cheers,
--
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