[Nut-upsdev] usbhid-ups fails with Belkin F6C120-UNV in nut-2.4.3

Arjen de Korte nut+devel at de-korte.org
Sat Mar 20 18:27:49 UTC 2010

Citeren Jon Burgess <jburgess777 op googlemail.com>:

> The change in SVN r2098 triggers the problem. By looking at the usbmon
> output I see that this device fails to respond to the get_report
> requests when the request size is 512 bytes.

Thanks for reporting this. Can you try if fixing the size to 8 bytes  
(instead of SMALLBUF) helps? You may wish to change both of the  
following lines in in 'drivers/libhid.c':

144 	        unsigned char   buf[8];
472 	        unsigned char   buf[8];

I vaguely remember that you can't read more than 8 bytes in a single  
operation, but I don't recall if this is a Belkin specific limitation  
or depends on the libusb version used.

Note that the logic that attempted to calculate the size of reports is  
flawed in earlier versions. Devices that would report more than the  
calculated size would find that these reports would be ignored  
completely. This isn't good either.

Best regards, Arjen
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