Re: [RFC 0/2] ACPI: Adding new acpi_driver type drivers ?

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Hi Hans,

On Sun, Feb 18, 2024 at 4:15 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> Hi Rafael,
> I recently learned that some Dell AIOs (1) use a backlight controller board
> connected to an UART. Canonical even submitted a driver for this in 2017:
> This UART has a DELL0501 HID with CID set to PNP0501 so that the UART is
> still handled by 8250_pnp.c. Unfortunately there is no separate ACPI device
> with an UartSerialBusV2() resource to model the backlight-controller.
> The RFC patch 2/2 in this series uses acpi_quirk_skip_serdev_enumeration()
> to still create a serdev for this for a backlight driver to bind to
> instead of creating a /dev/ttyS0.
> Like other cases where the UartSerialBusV2() resource is missing or broken
> this will only create the serdev-controller device and the serdev-device
> itself will need to be instantiated by the consumer (the backlight driver).
> Unlike existing other cases which use DMI modaliases to load on a specific
> board to work around brokeness of that board's specific ACPI tables, the
> intend here is to have a single driver for all Dell AIOs using the DELL0501
> HID for their UART, without needing to maintain a list of DMI matches.
> This means that the dell-uart-backlight driver will need something to bind
> to. The original driver from 2017 used an acpi_driver for this matching on
> and binding to the DELL0501 acpi_device.
> AFAIK you are trying to get rid of having drivers bind directly to
> acpi_device-s so I assume that you don't want me to introduce a new one.
> So to get a device to bind to without introducing a new acpi_driver
> patch 2/2 if this series creates a platform_device for this.
> The creation of this platform_device is why this is marked as RFC,
> if you are ok with this solution I guess you can merge this series
> already as is.


> With the caveat that the matching dell-uart-backlight
> driver is still under development (its progressing nicely and the
> serdev-device instantation + binding a serdev driver to it already
> works).
> If you have a different idea how to handle this I'm certainly open
> to suggestions.

I agree with the approach, thanks!

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