gpio_request will fail with error

[berndbenner]

Describe the bug

I am porting a gpio irq driver, working on rpi4/cm4 to rpi5/cm5.

Here is the code snippet to request the gpio:

/// gpio setup returns irq number
static int gpio_config(MYCONTEXT* md,int gpio) {
   int ret;
   int irqno;
   IRQCONTEXT* imd; 

   if ( (gpio<0) || (gpio>=NUM_GPIOS)) {
	  return -1;
   }
   imd=&md->irq_ctx[gpio];
   imd->gpio_no=gpio;
   ret=gpio_request(gpio,&imd->desc[0]);
   if (ret) {
      printk(KERN_ERR  "GPIO request failure: %s ret=%d\n", &imd->desc[0],ret);
      return ret;
   }
   irqno = gpio_to_irq(gpio);
   if ( irqno < 0 ) {
      printk(KERN_ERR "GPIO to IRQ mapping failure %s irqno=%d\n", &imd->desc[0],irqno);
      return -1;
   }
   imd->irq_number=irqno;
   printk(KERN_NOTICE  "Mapped gpio %d to intr no %d\n", gpio,irqno);
   return irqno;
}

If I call the routine with gpio=26 and descr. string "GPIO26", I get the following error return from gpio request:

root@rasp-cm5-000:/projects/rtflex# journalctl -k -f
Dec 18 12:37:26 rasp-cm5-000 kernel: gpioirq - registered Device number, Major: 90
Dec 18 12:38:58 rasp-cm5-000 kernel: Open was called!
Dec 18 12:38:58 rasp-cm5-000 kernel: gpioirq: IOCTL, command=1074283049(40084229), type=66, nr=41, dir=1, size=8, arg=7fffceedfc58
Dec 18 12:38:58 rasp-cm5-000 kernel: GPIO request failure: GPIO26 ret=-517

On rpi4/cm4 with older kernels this will work.

What went wrong ?

Steps to reproduce the behaviour

Try to request GPIO Pin in a kernel mode driver.

Device (s)

Raspberry Pi CM5

System

Raspberry Pi reference 2025-10-01
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 7dadcf1fc5ce1648ab09409ab978831690c9a955, stage4

2025/11/05 17:37:18
Copyright (c) 2012 Broadcom
version 57db150d (release) (embedded)

Linux rasp-cm5-000 6.12.47+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.12.47-1+rpt1 (2025-09-16) aarch64 GNU/Linux

facing the problem also on RPI5 and also with older kernel 6.13.37

Logs

No response

Additional context

No response

[6by9]

Error -517 is -EPROBE_DEFER (https://elixir.bootlin.com/linux/v6.18.1/source/include/linux/errno.h#L19). ie there is no driver loaded that declares that it serves that GPIO.

You appear to be trying to use the deprecated GPIO functions within the kernel which expected the internal GPIO number assignment to be static. The kernel moved away from that a good number of years ago as it doesn't work well when there are multiple GPIO provider drivers in the system.
The assignment of GPIOs hasn't been static for Pi0-4 since 6.6, and has never been static for Pi5. Checking on my Pi5 via /sys/class/gpio/, I have gpio providers starting at base numbers 512, 529, 535, 567, and 571. Ah, the forum post was at https://forums.raspberrypi.com/viewtopic.php?p=2166256#p2166256

gpio_request tries to map the internal GPIO number passed in gpio to a gpiochip which provides that GPIO. Trying to look up a value 26 in that case isn't going to work on Pi5.

The newer gpiod_ functions do provide mechanisms to look up a GPIO by name, but I can't see them immediately. You can also do that lookup from userspace using libgpiod ioctl GPIO_V2_GET_LINEINFO_IOCTL, hence why you can do gpioget GPIO26 and gpioinfo GPIO26.

[pelwell]

I am porting a gpio irq driver

What is this driver meant to do? Knowing the answer will help to guide you.

What went wrong ?

Time passed, and your driver didn't keep up.

1. The kernel's global number space has been deprecated for a very long time. A few released kernel versions ago we dropped the hack that forced the GPIOs on the 40-pin header to start at 0, so now they start at around 500 - look in /sys/class/gpio/. You are not meant to hardcode these numbers - they could change - and ideally you wouldn't use them at all, e.g....
2. GPIO descriptors (struct gpiod) are the preferred representation of GPIOs in the kernel. One would normally get them from settings in Device Tree using a call such as:

gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);

[berndbenner]

Thanks for your support!

The driver driver will provide ioclt-functions after initialization, to wait for gpio edges with or without a timeout. The ioclt functions will wait for a semphore, signalled by the gpio interrupt handler. A real time thread will wait for a gpio edge, to synchronize the software to the pulse timing of a fpga device on a hat-board. The old rpi4/cm4 driver was used to synchronize the software to the EtherCAT data update cycle of a microchip EtherCAT Slave HAT-board. This works well on kernel 6.1, I think also on kernel 6.6.
I need a api , to get the irq number of the gpio and setup the irq handler signaling the semaphore.
Is there a newer api providing this service?

[berndbenner]

I am also a little confused about the new gpio enumeration and chip naming, because pinctl and gpioinfo will report gpiochip0, gpiochip10 .. gpiochip13 and line numbers based on 0. Is there a api to get the right gpio-no. and/or chip no. to get the interrupt number of the gpio and setup the interrupt handler.