On Mon, Oct 09, 2017 at 08:09:19PM +0200, Marcel Holtmann wrote: > Hi Johan, > > >>>>>> UART devices is expected to be enumerated by SerDev subsystem. > >>>>>> > >>>>>> During ACPI scan, serial devices behind SPI, I2C or UART buses are not > >>>>>> enumerated, allowing them to be enumerated by their respective parents. > >>>>>> > >>>>>> Rename *spi_i2c_slave* to *serial_bus_slave* as this will be used for serial > >>>>>> devices on serial buses (SPI, I2C or UART). > >>>>>> > >>>>>> On Macs an empty ResourceTemplate is returned for uart slaves. > >>>>>> Instead the device properties "baud", "parity", "dataBits", "stopBits" are > >>>>>> provided. Add a check for "baud" in acpi_is_serial_bus_slave(). > >>>>>> > >>>>>> Signed-off-by: Frédéric Danis <frederic.danis.oss@xxxxxxxxx> > >>>>> > >>>>> So just to reiterate what I just mentioned in a comment to one of Hans's > >>>>> hci_bcm patches: > >>>>> > >>>>> This one would silently break PM for such devices on any system which > >>>>> does not have serdev enabled (as the corresponding platform devices > >>>>> would no longer be registered). And with serdev enabled, hciattach > >>>>> (btattach) would start failing as the tty device would no longer be > >>>>> registered (but I assume everyone is aware of that, and fine with it, by > >>>>> now). > >>>>> > >>>>> Perhaps the hci_bcm driver should start depending on > >>>>> SERIAL_DEV_CTRL_TTYPORT when ACPI is enabled? > >>>> > >>>> ACPI and DT both need SERIAL_DEV_CTRL_TTYPORT to work properly, > >>>> since SERIAL_DEV_CTRL_TTYPORT is the only controller implemented > >>>> for serdev. If any other controller is implemented that one could > >>>> also be used. > >>> > >>> Not for hci_bcm, right? This particular driver specifically depends on > >>> SERIAL_DEV_CTRL_TTYPORT for the ACPI devices and not just any (future) > >>> serdev controller (or currently working systems soon breaks silently). > >>> > >>> I don't think the same is true for the DT case where we do not already > >>> have child nodes defined in firmware (and in fact, this driver did not > >>> really support DT before serdev). > >> > >> The serdev ACPI support has been added to the core and not to > >> the ttyport and the hci_bcm driver only uses functions from the > >> core. As far as I can see the ACPI part would also work fine with > >> a different serdev controller. > > > > Indeed, but you need SERIAL_DEV_CTRL_TTYPORT to avoid silently breaking > > current ACPI setups which breaks when this patch is applied (as these > > devices all hang off of common serial ports managed by serial core). > > > >> Of course DT and ACPI currently require SERIAL_DEV_CTRL_TTYPORT, > >> since it's the only serdev controller implementation. Also it > >> covers most use cases. When SERIAL_DEV_BUS is selected it's > >> very likely, that you also want SERIAL_DEV_CTRL_TTYPORT. > > > >>>> I wonder if we should just hide SERIAL_DEV_CTRL_TTYPORT and enable > >>>> it together with SERDEV. I suspect that we won't see any other > >>>> controller (it would be a UART device, that is not registered as > >>>> tty device) in the next few years and the extra option seems to > >>>> confuse people. > >>> > >>> I agree that it is somewhat confusing. But now that we have both, > >>> perhaps simply having SERIAL_DEV_CTRL_TTYPORT default to "y" when > >>> SERIAL_DEV_BUS is selected could be a compromise. The Kconfig entry > >>> might need to be amended as well (e.g. if only to mention that you > >>> need to select a controller as well). > >> > >> I think we should at least add a default "y" if SERIAL_DEV_BUS. > > > > I'm preparing a patch. > > yes, please prepare a patch since the discussion spans multiple email > threads now. Lets get this back on track and find a patch that we are > all happy with. I submitted a patch amending the serdev Kconfig entries and making SERIAL_DEV_CTRL_TTYPORT default to Y when serdev support has been chosen. While that hopefully reduces the confusion regarding the Kconfig options somewhat, it's not really a fix for the potential silent hci_bcm regression that could result from this patch. [ The problem being that hci-attach would still succeed, but PM would be broken, when SERIAL_DEV_CTRL_TTYPORT is not set. ] I mentioned that making HCI_BCM depend on SERIAL_DEV_CTRL_TTYPORT might be used to avoid this situation, although it is on some level is conceptually wrong to describe runtime dependencies in Kconfig (cf. having a USB device driver, depend on a particular host controller rather than just USB support). I'll write something like that up in a patch for Bluetooth and you can decide if you want to apply it to remedy this particular situation, though. Johan -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
