mt76x0u: Probing issues on Raspberry Pi 3 B+
Quoted 9 lines · Alan Stern
Quoted 6 lines · Lorenzo Bianconi
Here it is a different issue respect to the AMD IOMMU one, dwc2 host driver does not implement SG I/O so probing fails. I guess it is still useful to implement a 'legacy' mode that enable mt76 on host controllers that do not implement SG I/O (rpi is a very common device so it will be cool to have mt76 working on it). Moreover we are not removing functionalities, user experience will remain the same
Quoted 3 lines
Has anyone considered adding SG support to dwc2? It shouldn't be very difficult. The corresponding change for ehci-hcd required adding no more than about 30 lines of code.
That would be cool. Perhaps somebody with dwc2 hardware could do this.
However in mt76x02u we possibly would like to support other usb host drivers with sg_tablesize = 0 . I would like to clarify what is correct to do with such drivers.
Is ok to pass buffer via urb->sg with urb->num_sgs = 1 ? Or maybe urb->num_sgs should be 0 to pass buffer via urb->sg on such drivers ? Or maybe non of above is correct and the only option that will work in 100% is pass buffer via urb->transfer_buffer ?
Stanislaw