Hello,
My question is regarding 2.4.20 kernel , but as I looked of 2.6 kernel code , it's
seems also relevant.
the descriptor struct size is 18 bytes (it is the descriptor member is usb_device struct (struct usb_device_descriptor) ;
I see tha in usb.c , in usb_new_device() , there's a call to
usb_get_descriptor(dev, USB_DT_DEVICE, 0, &dev->descriptor, 8)
(Note : the last paramter, 8 , means that we read only 8 bytes instead of 18 , the real size)
and afterwards
dev->epmaxpacketin [0] = dev->descriptor.bMaxPacketSize0; dev->epmaxpacketout[0] = dev->descriptor.bMaxPacketSize0;
err = usb_get_device_descriptor(dev);
Why is the first call with 8 bytes, than setting of epmaxpacketin [0]/epmaxpacketout [0] ,
and then again a call to usb_get_device_descriptor() , wheras this second call in fact calls
usb_get_descriptor() with size 18 ?
What is wrong with reading 18 bytes , the full structure, at first try ?
I saw some posting in this forum (from quite a long time ago); They say there that you should not
try to read length higher than length in fact (like 128); I agree; But why not to read tha actual length , 18?
regards Sting
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