pdconf seems leaked here.

for all the early return below, except the if (ret < 0), pdconf needs being free()'d?

do you mean multiply the multiplier?

Returns the packet size on success,

Upstream return only

• \returns the wMaxPacketSize value
• \returns \ref LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
• \returns \ref LIBUSB_ERROR_OTHER on other failure

Upstream return ep->wMaxPacketSize only when the device isn't a SuperSpeed device or retrieving the SS endpoint didn't worked.

So

• USB3 ep + get companion descriptor failed will access wMaxPacketSize not return error.
• USB3 BULKIN ep + (ss_ep->wBytesPerInterval = 0) + (ep->wMaxPacketSize = 1024) return 0 not 1024.

587 libusb speed api
603 libusb20 speed api
use the same one?

Upstream

• \returns the maximum packet size which can be sent/received on this endpoint
• \returns \ref LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
• \returns \ref LIBUSB_ERROR_OTHER on other failure

endpoint is bEndpointAddress not index

Ditto.

Upstream returns

• \returns the maximum packet size which can be sent/received on this endpoint
• \returns \ref LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
• \returns \ref LIBUSB_ERROR_OTHER on other failure

Ditto.

I think it is much better to have detailed error other than error from upstream implementation.

See above. And second one makes sense.

Same as above

You are right, thanks!

Same as above

Same as above

Same as above.