Re: Report ID problem with HID-RAW interface usage

[Amit Nagal <helloin.amit-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

> I'm going to challenge this. I looked at the report descriptor you attached,
> and I don't think it really works the way you think it does. What it looks
> like to me is separate reports expecting separate data, not a bunch of
> reports all expecting the same data but of different lengths. What you
> describe would be fairly non-standard, IMO.
>


Sorry , i did not get what is meant by "a bunch of reports all
expecting same data
but of different lengths " . what is the meaning of this phrase "same data"  .

ya i agree if the device supports separate reports ,
theoretically each one should be there to serve separate data .
otherwise a device can define a report of max size N and all transactions
can take place with it .
but if a device support only one report of max size N
the drawback is that even to send  a very small report data (say 4-5 bytes ) ,
we have to use max size N report always , which may waste considerable
bandwidth .

Now in my case yes mostly different reports carry different data only .
as i told previously , the payload protocol is in the form  <command >
<response >.

by this i mean let say if i want to fetch ipod root folder entries
(filenames ),
i will send a command for that in a output report and device will send
root folder entries
in input reports .

so different payload commands are send over different reports only .

But again , the defining parameter that a report N should be used is
data payload len only . so if 2 payload commands have
same size , both can be send using same report ID .
and this thing is already working for me  .

> What I would suggest for the short-term is this:
> With the device you have, send data based on the HID descriptor you attached
> to the last email. I mean manually. In the case of your descriptor: if the
> report length you want to send is <= 5, use report 1; If it's <= 9, use
> report 2; if it's <= 13, use report 3; if it's <= 17, use report 4; if it's
> <= 25, use report 5, etc.
>

Yes , this approach is already working for me .
with the above mentioned approch ( <= 5 use report 1 , <=9  use report 2) and
using hidraw interface  , i am able to transact a few basic payload
commands with the device .
infact even the device is sending different payload command <Responses >
using the same < Report ID > .

May be i am wrong , due to lack of documentation regarding the
presence of different report ID ,
but i am able to transact with the device using the above mentioned
approach of sending
payload data in  a report whose size is >= data payload len .

if desired , i can send dmesg logs also depicting the same .

Thanx & Regards
Amit Nagal
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