gpio: Remove unused and obsoleted irq_to_gpio()

irq_to_gpio() is legacy and unused API, remove it for good.

This leaves gpio_to_irq() as it's used yet in many places.
Nevertheless, removal of its counterpart is a good signal
to whoever even trying to consider using them that do not.

Signed-off-by: Andy Shevchenko <[e-mail]>
Acked-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

Documentation/driver-api/gpio/legacy.rst

···
 	/* map GPIO numbers to IRQ numbers */
 	int gpio_to_irq(unsigned gpio);
 
-	/* map IRQ numbers to GPIO numbers (avoid using this) */
-	int irq_to_gpio(unsigned irq);
-
 Those return either the corresponding number in the other namespace, or
 else a negative errno code if the mapping can't be done.  (For example,
 some GPIOs can't be used as IRQs.)  It is an unchecked error to use a GPIO
···
 devices, by the board-specific initialization code.  Note that IRQ trigger
 options are part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are
 system wakeup capabilities.
-
-Non-error values returned from irq_to_gpio() would most commonly be used
-with gpio_get_value(), for example to initialize or update driver state
-when the IRQ is edge-triggered.  Note that some platforms don't support
-this reverse mapping, so you should avoid using it.
 
 
 Emulating Open Drain Signals

Documentation/translations/zh_CN/driver-api/gpio/legacy.rst

···
 	/* 映射 GPIO 编号到 IRQ 编号 */
 	int gpio_to_irq(unsigned gpio);
 
-	/* 映射 IRQ 编号到 GPIO 编号 (尽量避免使用) */
-	int irq_to_gpio(unsigned irq);
-
 它们的返回值为对应命名空间的相关编号，或是负的错误代码(如果无法映射)。
 (例如,某些 GPIO 无法做为 IRQ 使用。)以下的编号错误是未经检测的:使用一个
 未通过 gpio_direction_input()配置为输入的 GPIO 编号，或者使用一个
···
 它们通常通过板级特定的初始化代码存放到平台设备的 IRQ 资源中。注意:IRQ
 触发选项是 IRQ 接口的一部分，如 IRQF_TRIGGER_FALLING，系统唤醒能力
 也是如此。
-
-irq_to_gpio()返回的非错误值大多数通常可以被 gpio_get_value()所使用，
-比如在 IRQ 是沿触发时初始化或更新驱动状态。注意某些平台不支持反映射,所以
-你应该尽量避免使用它。
 
 
 模拟开漏信号

Documentation/translations/zh_TW/gpio.txt

···
 	/* 映射 GPIO 編號到 IRQ 編號 */
 	int gpio_to_irq(unsigned gpio);
 
-	/* 映射 IRQ 編號到 GPIO 編號 (儘量避免使用) */
-	int irq_to_gpio(unsigned irq);
-
 它們的返回值爲對應命名空間的相關編號，或是負的錯誤代碼(如果無法映射)。
 (例如,某些 GPIO 無法做爲 IRQ 使用。)以下的編號錯誤是未經檢測的:使用一個
 未通過 gpio_direction_input()配置爲輸入的 GPIO 編號，或者使用一個
···
 它們通常通過板級特定的初始化代碼存放到平台設備的 IRQ 資源中。注意:IRQ
 觸發選項是 IRQ 接口的一部分，如 IRQF_TRIGGER_FALLING，系統喚醒能力
 也是如此。
-
-irq_to_gpio()返回的非錯誤值大多數通常可以被 gpio_get_value()所使用，
-比如在 IRQ 是沿觸發時初始化或更新驅動狀態。注意某些平台不支持反映射,所以
-你應該儘量避免使用它。
 
 
 模擬開漏信號

arch/m68k/include/asm/gpio.h

···
 		return __gpio_to_irq(gpio);
 }
 
-static inline int irq_to_gpio(unsigned irq)
-{
-	return (irq >= MCFGPIO_IRQ_VECBASE &&
-		irq < (MCFGPIO_IRQ_VECBASE + MCFGPIO_IRQ_MAX)) ?
-		irq - MCFGPIO_IRQ_VECBASE : -ENXIO;
-}
-
 static inline int gpio_cansleep(unsigned gpio)
 {
 	return gpio < MCFGPIO_PIN_MAX ? 0 : __gpio_cansleep(gpio);

arch/sh/include/asm/gpio.h

···
 	return __gpio_to_irq(gpio);
 }
 
-static inline int irq_to_gpio(unsigned int irq)
-{
-	return -ENOSYS;
-}
-
 #endif /* CONFIG_GPIOLIB */
 
 #endif /* __ASM_SH_GPIO_H */

include/linux/gpio.h

···
 	return __gpio_to_irq(gpio);
 }
 
-static inline int irq_to_gpio(unsigned int irq)
-{
-	return -EINVAL;
-}
-
 #endif /* ! CONFIG_ARCH_HAVE_CUSTOM_GPIO_H */
 
 /* CONFIG_GPIOLIB: bindings for managed devices that want to request gpios */
···
 static inline int gpio_to_irq(unsigned gpio)
 {
 	/* GPIO can never have been requested or set as input */
-	WARN_ON(1);
-	return -EINVAL;
-}
-
-static inline int irq_to_gpio(unsigned irq)
-{
-	/* irq can never have been returned from gpio_to_irq() */
 	WARN_ON(1);
 	return -EINVAL;
 }