On 18/06/2020 18:25, Jeff Chase wrote: > On Thu, Jun 18, 2020 at 3:05 AM Hans Verkuil <hverkuil-cisco@xxxxxxxxx> wrote: >> >> On 18/06/2020 10:59, Jeff Chase wrote: >>> Hi Hans, >>> >>> We are using two of these in an Intel-based Chromebox. I see that the >>> cros-ec and seco drivers just statically define the PCI BDF of the >>> Intel graphics device for their boards. I don't see an example of ACPI >>> passing this information. I can copy cros-ec and seco by adding a >>> board table and then use the UID of each device to select the correct >>> port. Adding board-specific configuration to the driver doesn't seem >>> ideal but I'm not sure what the proper way to pass this using ACPI is. >> >> You are right, it's not ACPI, it's using DMI matching. >> >> I have zero knowledge about ACPI, so I have no idea if there is some standard >> method of retrieving this association via ACPI. > > I'm not very familiar with ACPI either. I looked for but did not find > an ACPI equivalent of_get_mac_address(). > > I believe it's possible to reference the PCI node but it would take a > bit of work on both the coreboot and linux side. > >> >> This particular chip can actually be used both with DMI matching but also >> on an ARM with device tree, but since you can't test this on an ARM board, >> there is no point in adding support for that. >> >> However, compared to the cros-ec and seco drivers you can do something a bit >> different here: those drivers just return -ENODEV if there is no match, but >> since this driver reads the EDID it can just continue as long as it does not >> set the CEC_CAP_CONNECTOR_INFO capability. > > Is it necessary to add support if we don't set CEC_CAP_CONNECTOR_INFO? It is very desirable. Otherwise userspace will not know which CEC device is associated with which HDMI device. Since you are using two of these chips for a Chromebox, I suspect that you actually need to support this. Also, I am (slowly) working on wiring support for this in all CEC transmitter drivers, so I prefer not to add CEC drivers without support for this. I really should have noticed much earlier that support for this was missing. My apologies for that. Regards, Hans
