Re: [PATCH RESEND] USB HID: Add ID for eGalax Multitouch used in JooJoo tablet

Le 16 août 10 à 17:17, Stéphane Chatty a écrit :

Le 16 août 10 à 15:58, Jiri Kosina a écrit :

quoted

thanks for the analysis. How do devices in their report descriptor
describe the fact whether the events should be interleaved by sync  
or not?

As far as I know, they don't. I know of two multitouch devices that  
send groups of fingers over several HID messages:
 - the 3M 22" panel, when there are more than 6 fingers on the  
panel. You know there are more messages coming when the number of  
fingers (reported through ContactCount in the first message) is  
greater than 6.
 - the eGalax 72xx series, that adds a second message whenever  
there are two fingers; I am not sure yet how one knows when to  
wait  for a second message. Mathieu might be able to tell us.

Oops... as usual, publishing an opinion is a good way of finding out  
how it be can wrong :-) I just figured that if ContactMax is  
available for all devices as well as ContactCount, then there is a  
way of knowing:
  - if ContactMax is greater than the number of fingers in the report  
descriptors, then you know that sometimes you'll get multiple messages.
  - if ContactCount in a message is greater than the number of  
fingers in the report descriptors, then you know you'll need to read  
more messages after this one.

We'll need to check this with all the known devices...

Cheers,

St.

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