Re: [PATCH v5 2/2] media: cec: i2c: ch7322: Add ch7322 CEC controller driver

[Jeff Chase <jnchase@google.com>]

On Thu, Jun 18, 2020 at 3:05 AM Hans Verkuil <hverkuil-cisco@xs4all.nl> 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?

Thanks,
Jeff