On Fri, 20 Jun 2003 14:22:10 -0600
Jackson Chan <[EMAIL PROTECTED]> wrote:
> > > Secondly, I am trying to write a single output report to my device
> > > that contains 5 bytes of data{0x13,0x13,0,0,0} through the Control
> > > (0) endpoint via a SetReport command. I tried using hidiocsusage
> > > and hidiocsreport, but could not(& don't know how to) get it
> > > working.
> >
> > What does this mean (in terms of the report data items)?
> > Please show the HID descriptor for your device - what report fields
> > does it have?
>
> dmesg shows this:
>
> OUTPUT[OUTPUT]
> Field(0)
> Usage(1)
> Digitizers.0000
> Logical Minimum(0)
> Logical Maximum(255)
> Report Size(8)
> Report Count(5)
> Report Offset(0)
> Flags( Variable Absolute BufferedByte )
>
> So Count = 5 and each values size = 8. {0x13,0x13,0x00,0x00,0x00}
This looks like a bug/misfeature in hiddev - it does not support items
with Report Count > 1.
hiddev_usage_ref::usage_index is treated as an index of a usage in the
selected data item (and limited by hid_field::maxusage), and also used
as an index into the hid_field::value array. However, the number of
usages for a data item may be less than the number of values - see the
HID spec 1.11, page 40 (50):
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).
So the configuration with one usage and 5 values (as seen in the report
descriptor above) is legal. However, the current hiddev API does not
have a way to work with such devices.
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