Hi Marcel, On Tue, Feb 24, 2015 at 7:18 PM, Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote: > Hi Jakub, > >> When I do interleaved scan on linux, it's doing LE first, for around >> 10 seconds, and then Classic scan for another few seconds on kernel >> level. >> >> I was playing with Bluetooth on macbook, and noticed that they do both >> LE and Classic scan at once. So I tried modifying kernel, I triggered >> both LE and classic scan at once by queuing both >> HCI_OP_LE_SET_SCAN_ENABLE, and HCI_OP_INQUIRY and it just worked, both >> LE and Classic devices were reported. >> >> I tested that with CSR, Broadcom and Atheros chips, and all behaved well. >> >> Is there any reason why we do interleave instead of both scans at once ? > > actually there are chips that do not support BR/EDR inquiry and LE scan at the same time. So for some chips we need this behavior. I think that all chips in platforms running Windows 8 will actually support simultaneous BR/EDR inquiry and LE scan since Microsoft mandated it. However in the embedded SoC world that might not be true actually. > > And in the early days of LE, there was almost no chip that was able to handle BR/EDR inquiry and LE scan at the same time. That is why the interleaved behavior exists in the first place. > >> I would be more than happy to modify 'interleaved' behaviour, to do >> both LE and classic scan at same time. > > Introduce HCI_QUIRK_SIMULTAENOUS_DISCOVERY and allow for well know good behaving controller to set it. That way we can slowly move into that direction and keep interleaved behavior as a fallback. > > Regards > > Marcel > So I send my patches previous week, and I just uploaded new version. The old version was just starting both scans at once. It was working on Atheros, CSR, and Broadcom, but then I find out it doesn't work on Intel controllers. The reason for that was LE scan window equal to LE scan interval. When I doubled Scan Interval, Intel devices started working. Apparently other controllers don't really care. So now it works on all controllers I have tested with. I have however question about Broadcom: Simultaenous scan work, when there is firmware patch in /lib/firmware (ubuntu have it). If the patch is not present it's not working. Can I somehow make this kind of check in btusb.c to set the quirk ? I also have question about scan window and interval: right now I just doubled scan interval. This gives more than 12ms of free time that BR/EDR scan would use to do inquiry. I fund in spec (Version 4.2 [Vol 2, Part E] 6.2 and 6.3) that default Inquiry_Scan_Window is 11.25ms, so this should work good. Do you have any suggestions to tune those parameters in other way ? -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
