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While trying to set up an SSDT override for a USB-2-I2C chip [0], I realized that the function acpi_gpiochip_find() was using the parent of the gpio_chip to do the ACPI matching. This works fine on my Ice Lake laptop because AFAICT, the DSDT presents the PCI device INT3455 as the "Device (GPI0)", but is in fact handled by the pinctrl driver in Linux. The pinctrl driver then creates a gpio_chip device. This means that the gc->parent device in that case is the GPI0 device from ACPI and everything works. However, in the hid-cp2112 case, the parent is the USB device, and the gpio_chip is directly under that USB device. Which means that in this case gc->parent points at the USB device, and so we can not do an ACPI match towards the GPIO device. I think it is safe to resolve the ACPI matching through the fwnode because when we call gpiochip_add_data(), the first thing it does is setting a proper gc->fwnode: if it is not there, it borrows the fwnode of the parent. So in my Ice Lake case, gc->fwnode is the one from the parent, meaning that the ACPI handle we will get is the one from the GPI0 in the DSDT (the pincrtl one). And in the hid-cp2112 case, we get the actual fwnode from the gpiochip we created in the HID device, making it working. Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Link: https://lore.kernel.org/linux-input/20230227140758.1575-1-kaehndan@gmail.com/T/#m592f18081ef3b95b618694a612ff864420c5aaf3 [0] Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.