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

Arjen de Korte nut+devel at de-korte.org
Sun Mar 21 10:49:55 UTC 2010

Citeren Jon Burgess <jburgess777 op googlemail.com>:

>> Several years ago on the linux-usb list, it was often pointed out that
>> the kernel was supposed to honor the wMaxPacketSize field, and
>> fragment the requests accordingly. While this was suggested for
>> performance reasons (fewer round trips between user and kernel space),
>> it should still hold true for less frequent transfers.
> In this case we are reading the data, I don't know if there is much the
> kernel can do to fragment this, I don't see any concept of an offset
> field when reading the report.

There is no need for an offset field. If you read/write the same  
report again and the device will return/accept the next chunk of data.  
The drawback here is that this most likely lead to a timeout after the  
last available data has been read on the next read operation. We need  
to deal with that.

Best regards, Arjen
Please keep list traffic on the list

More information about the Nut-upsdev mailing list