On Wed, May 8, 2024 at 5:44 PM Andy Shevchenko <andy@xxxxxxxxxx> wrote: > > On Wed, May 08, 2024 at 12:42:05PM +0800, Kai-Heng Feng wrote: > > [+Cc AceLan] > > On Wed, Apr 24, 2024 at 5:58 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > > On 4/24/24 10:04 AM, Kai-Heng Feng wrote: > > > > On Sun, Feb 18, 2024 at 11:15 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: > > > >> https://lkml.org/lkml/2017/10/26/78 > > > >> > > > >> 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). > > > > > > > > I was about to work on this and found you're already working on it. > > > > > > > > Please add me to Cc list when the driver is ready to be tested, thanks! > > > > > > I hope you have access to actual hw with such a backlight device ? > > > > > > The driver actually has been ready for testing for quite a while now, > > > but the person who reported this backlight controller not being > > > supported to me has been testing this on a AIO of a friend of theirs > > > and this has been going pretty slow. > > > > > > So if you can test the driver (attached) then that would be great :) > > > > > > I even wrote an emulator to test it locally and that works, so > > > assuming I got the protocol right from the original posting of > > > the driver for this years ago then things should work. > > > > > > Note this depends on the kernel also having the patches from this > > > RFC (which Rafael has already merged) applied. > > > > There are newer AIO have UID other than 0, like "SIOBUAR2". > > > > Once change the "0" to NULL in 'get_serdev_controller("DELL0501", "0", > > 0, "serial0");', everything works perfectly. > > > > With that change, > > Tested-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> > > Do we have tables with _UID set to 0? > If so, we would need more complex approach. Yes, some tables have _UID set to 0 and some have other _UID values. Kai-Heng > > -- > With Best Regards, > Andy Shevchenko > >
