Fix of_gpio compat shim build with CONFIG_OF_GPIO - #1288
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The compat of_get_named_gpio() added for kernels that no longer ship
linux/of_gpio.h (removed by commit 51aaf65bbd21, "gpio: of: Remove
<linux/of_gpio.h>", v7.1-rc1) declares its __to_hwgpio() helper as taking
a const struct gpio_device *. gpio_device_get_chip() has taken a mutable
struct gpio_device * ever since it was introduced by commit 9b418780844c
("gpiolib: reluctantly provide gpio_device_get_chip()"), so the call
inside the CONFIG_OF_GPIO block discards the qualifier:
common/inc/nv-linux.h:1737:51: error: passing 'const struct gpio_device *'
to parameter of type 'struct gpio_device *' discards qualifiers
[-Werror,-Wincompatible-pointer-types-discards-qualifiers]
That block is only reachable on kernels >= 7.1 built with CONFIG_OF_GPIO,
which is why the desktop x86 configurations do not hit it.
The const buys nothing: the only caller, the compat of_get_named_gpio()
right below, holds a mutable gdev from gpio_device_find_by_fwnode(). Drop
it rather than casting it away.
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kernel-openfails to build against Linux 7.1 with clang when the kernel is configured withCONFIG_OF_GPIO=y.610.57.04 added a compat
of_get_named_gpio()for kernels that no longer shiplinux/of_gpio.h(removed by51aaf65bbd21, "gpio: of: Remove<linux/of_gpio.h>", v7.1-rc1). Its helper__to_hwgpio()takes aconst struct gpio_device *, butgpio_device_get_chip()has taken a mutablestruct gpio_device *ever since9b418780844c("gpiolib: reluctantly provide gpio_device_get_chip()"), so the call inside theCONFIG_OF_GPIOblock discards the qualifier:Three conditions have to line up, which is presumably why it slipped through:
linux/of_gpio.his absent, i.e. on kernels >= 7.1;CONFIG_OF_GPIO=y, which the usual x86 configurations leave off (it isdef_bool yunderCONFIG_OF, and distributions that enable device tree support on x86 for overlays get it implicitly);scripts/Makefile.warnadds-Werror=incompatible-pointer-typesunconditionally, and clang has-Wincompatible-pointer-types-discards-qualifiersinside that group. GCC reports the same code under the separate-Wdiscarded-qualifiers, which the flag does not cover, so GCC builds only warn.WARNINGS_AS_ERRORSis not involved.The
constis not load-bearing: the only caller is the compatof_get_named_gpio()a few lines below, and it holds a mutablegdevfromgpio_device_find_by_fwnode(). Dropping the qualifier is preferable to casting it away at the call site. The only consumer ofof_get_named_gpio()in the tree isnvidia/nv-dsi-parse-panel-props.c, which is Tegra-only, so x86 behaviour is unaffected either way.Verified by building the open modules of 610.57.04 against Linux 7.1.6 with clang 21 and
CONFIG_OF_GPIO=y: the build fails as above without this change and completes with it.