I am using Raspberry pi 4b with Linux raspberrypi 5.10.63-v7l+. I am writing simple userspace program for control one GPIO by ioctl() (in my case GPIO 13 for example). However program responses: Device or resource busy when I try to handle it.
The investigation shows that all pins on gpiochip0 are occupied by sysfs:
root@raspberrypi:/home/pi# cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 0-57, parent: platform/fe200000.gpio, pinctrl-bcm2711:
gpio-0 (ID_SDA )
gpio-1 (ID_SCL )
gpio-2 (SDA1 |sysfs ) in hi
gpio-3 (SCL1 |sysfs ) in hi
gpio-4 (GPIO_GCLK |sysfs ) in hi
gpio-5 (GPIO5 |sysfs ) in hi
gpio-6 (GPIO6 |sysfs ) in hi
gpio-7 (SPI_CE1_N |spi0 CS1 ) out hi ACTIVE LOW
gpio-8 (SPI_CE0_N |spi0 CS0 ) out hi ACTIVE LOW
gpio-9 (SPI_MISO |sysfs ) in lo
gpio-10 (SPI_MOSI |sysfs ) in lo
gpio-11 (SPI_SCLK |sysfs ) in lo
gpio-12 (GPIO12 |sysfs ) in lo
gpio-13 (GPIO13 |sysfs ) in lo
gpio-14 (TXD1 |sysfs ) in hi
gpio-15 (RXD1 |sysfs ) in hi
gpio-16 (GPIO16 |sysfs ) in lo
gpio-17 (GPIO17 |sysfs ) in lo
gpio-18 (GPIO18 |sysfs ) in lo
gpio-19 (GPIO19 |sysfs ) in lo
gpio-20 (GPIO20 |sysfs ) in lo
gpio-21 (GPIO21 |sysfs ) in lo
gpio-22 (GPIO22 |sysfs ) in lo
gpio-23 (GPIO23 |sysfs ) in lo
gpio-24 (GPIO24 |sysfs ) in lo
gpio-25 (GPIO25 |sysfs ) in lo
gpio-26 (GPIO26 |sysfs ) in lo
gpio-27 (GPIO27 |sysfs ) in lo
gpio-28 (RGMII_MDIO )
gpio-29 (RGMIO_MDC )
gpio-30 (CTS0 )
gpio-31 (RTS0 )
gpio-32 (TXD0 )
gpio-33 (RXD0 )
gpio-34 (SD1_CLK )
gpio-35 (SD1_CMD )
gpio-36 (SD1_DATA0 )
gpio-37 (SD1_DATA1 )
gpio-38 (SD1_DATA2 )
gpio-39 (SD1_DATA3 )
gpio-40 (PWM0_MISO )
gpio-41 (PWM1_MOSI )
gpio-42 (STATUS_LED_G_CLK |led0 ) out lo
gpio-43 (SPIFLASH_CE_N )
gpio-44 (SDA0 )
gpio-45 (SCL0 )
gpio-46 (RGMII_RXCLK )
gpio-47 (RGMII_RXCTL )
gpio-48 (RGMII_RXD0 )
gpio-49 (RGMII_RXD1 )
gpio-50 (RGMII_RXD2 )
gpio-51 (RGMII_RXD3 )
gpio-52 (RGMII_TXCLK )
gpio-53 (RGMII_TXCTL )
gpio-54 (RGMII_TXD0 )
gpio-55 (RGMII_TXD1 )
gpio-56 (RGMII_TXD2 )
gpio-57 (RGMII_TXD3 )
gpiochip1: GPIOs 504-511, parent: platform/soc:firmware:gpio, raspberrypi-exp-gpio, can sleep:
gpio-504 (BT_ON )
gpio-505 (WL_ON )
gpio-506 (PWR_LED_OFF |led1 ) out lo ACTIVE LOW
gpio-507 (GLOBAL_RESET )
gpio-508 (VDD_SD_IO_SEL |vdd-sd-io ) out hi
gpio-509 (CAM_GPIO )
gpio-510 (SD_PWR_ON |sd_vcc_reg ) out hi
gpio-511 (SD_OC_N
same thing if try to run gpioinfo:
pi@raspberrypi:~ $ gpioinfo
gpiochip0 - 58 lines:
line 0: "ID_SDA" unused input active-high
line 1: "ID_SCL" unused input active-high
line 2: "SDA1" "sysfs" input active-high [used]
line 3: "SCL1" "sysfs" input active-high [used]
line 4: "GPIO_GCLK" "sysfs" input active-high [used]
line 5: "GPIO5" "sysfs" input active-high [used]
line 6: "GPIO6" "sysfs" input active-high [used]
line 7: "SPI_CE1_N" "spi0 CS1" output active-low [used]
line 8: "SPI_CE0_N" "spi0 CS0" output active-low [used]
line 9: "SPI_MISO" "sysfs" input active-high [used]
line 10: "SPI_MOSI" "sysfs" input active-high [used]
line 11: "SPI_SCLK" "sysfs" input active-high [used]
line 12: "GPIO12" "sysfs" input active-high [used]
line 13: "GPIO13" "sysfs" input active-high [used]
line 14: "TXD1" "sysfs" input active-high [used]
line 15: "RXD1" "sysfs" input active-high [used]
line 16: "GPIO16" "sysfs" input active-high [used]
line 17: "GPIO17" "sysfs" input active-high [used]
line 18: "GPIO18" "sysfs" input active-high [used]
line 19: "GPIO19" "sysfs" input active-high [used]
line 20: "GPIO20" "sysfs" input active-high [used]
line 21: "GPIO21" "sysfs" input active-high [used]
line 22: "GPIO22" "sysfs" input active-high [used]
line 23: "GPIO23" "sysfs" input active-high [used]
line 24: "GPIO24" "sysfs" input active-high [used]
line 25: "GPIO25" "sysfs" input active-high [used]
line 26: "GPIO26" "sysfs" input active-high [used]
line 27: "GPIO27" "sysfs" input active-high [used]
The situation is strange because first minute after kernel restart gpio pins are not occupied and I can run my program but then somehow they become "used" by sysfs. Even if I don't run any program situation is same. Of course it is possible to unexport each pin by echo in sysfs and run my program without problem but I can't understand reason of this behavior. How to find who is occupying gpiochip0?
