Thanks for your time.
Alan Stern wrote:
> You must not have sent a Set-Port-Feature request. This warning gets
> invoked only when the recipient part of bRequestType is ENDPOINT or
> INTERFACE, and for Set-Port-Feature the recipient is OTHER.
[...]
> You are allowed to send control messages whose recipient is anything other
> than ENDPOINT or INTERFACE, and you are allowed to send those as well if
> the type is VENDOR.
Could you please take a deep breath, Alan? I think that I am not your
enemy, never. It would be good if we share the problem and cooperate
together.
Your explanation (what I quoted here) is correct. But the my
requirement is not only for Set-Port-Feature, but also for
Clear-Port-Feature.
Here is some more explanation to the people who have interest on this
topic.
We need to send a Clear-Port-Feature to turn off the port power, and a
Set-Port-Feature to turn on the port power. That's my understanding.
(When I connect my hub, the port power is on.)
The answer of the quiz is that when I didn't success with libusb
library, my invocation was with USB_REQ_CLEAR_FEATURE.
Right, in drivers/usb/core/devio.c, there is a function
check_ctrlrecip, and only when requesttype is ENDPOINT or INTERFACE,
it is checked. Here is a quote of a part of check_ctrlrecip:
switch (requesttype & USB_RECIP_MASK) {
case USB_RECIP_ENDPOINT:
if ((ret = findintfep(ps->dev, index)) >= 0)
ret = checkintf(ps, ret);
break;
case USB_RECIP_INTERFACE:
ret = checkintf(ps, index);
break;
}
What's USB_RECIP_MASK? It is defined in include/linux/usb_ch9.h:
#define USB_RECIP_MASK 0x1f
#define USB_RECIP_DEVICE 0x00
#define USB_RECIP_INTERFACE 0x01
#define USB_RECIP_ENDPOINT 0x02
#define USB_RECIP_OTHER 0x03
And the values of Clear-Port-Feature and Set-Port-Feature are:
#define USB_REQ_CLEAR_FEATURE 0x01
#define USB_REQ_SET_FEATURE 0x03
Yes, it is OTHER for Set-Port-Feature. It is INTERFACE for
Clear-Port-Feature.
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