I wrote a driver that exposes I2C registers via an IIO device, this device operates in direct mode (read/write directly to files in sysfs), the files are correctly created in sysfs and work fine. I would like to expose these files in a user-friendly way, I was thinking of creating symlinks to the sysfs files with a udev rule so that instead of having to read /sys/bus/i2c/devices/5-0042/iio\:device1/in_pressure_raw the user can read from a file like /run/the_tank/pressure. What's the best place for such files? /dev? /run?

I have set up an i2c protocol which detects the mpu9250 at address 0x68. Now I want to configure the mpu and I have updated my dts file with the following lines of code: mpu9250@68 { compatible = "invensense,mpu9250"; reg = ; i2c-gate { #address-cells = ; #size-cells = ; ax8975@c { compatible = "ak,ak8975"; reg = ; }; }; }; However, I get the following error on running >> dmesg | grep mpu >> inv-mpu6050-i2c 1-0068: invalid whoami 0x40 expected 0x71 (MPU9250) For this I have also configured the i2cmux and Industrial I/O (IIO) through the developer shell with the "make menuconfig" command. But I see no expected results. Where could I have possibly gone wrong?

I have made a custom Linux image with Yocto for use with CN0540 and DE10-Nano. The manufacturer of the CN0540 (Analog Devices) provides an evaluation image for the board, which works without issue, however in my custom image which is using the same kernel fork (ADI Linux fork ), the same defconfig as far as I can tell (socfpga_adi_defconfig), and the same device tree (CN0540 dts ), and also the same HDL is loaded on the FPGA (CN0540 HDL ) I can't use the buffer from the ADC on the CN0540 (AD7768-1). I can read a single value from the ADC, either with libiio's iio_info command, or with the device file at sys/bus/iio/devices/iio:device0/in_voltage0_raw, but I can't read from the buffer of the device E.g iio_readdev ad7768-1 returns Unable to refill buffer: Connection timed out (110), or doing

> echo 1 > scan_elements/in_voltage0_en
> echo 1 > buffer/enable
> cat /dev/iio:device0 | hexdump

which causes the device to crash, unless I set the length of the buffer to 1 with echo 1 > buffer/length which causes the device to output

[  441.310599] rcu: INFO: rcu_sched self-detected stall on CPU
[  441.316258] rcu:     0-....: (2099 ticks this GP) idle=10f/1/0x40000002 softirq=2509/2509 fqs=1033
[  441.325163]  (t=2100 jiffies g=497 q=7)
[  441.329057] NMI backtrace for cpu 0
[  441.332592] CPU: 0 PID: 163 Comm: cat Not tainted 5.15.0-yocto-standard-adi #1
[  441.339927] Hardware name: Altera SOCFPGA
[  441.343988] Backtrace:
[  441.346453] [] (dump_backtrace) from [] (show_stack+0x20/0x24)
[  441.354073]  r7:c010edfc r6:00000000 r5:60070193 r4:c143b218
[  441.359801] [] (show_stack) from [] (dump_stack_lvl+0x48/0x54)
[  441.367360] [] (dump_stack_lvl) from [] (dump_stack+0x18/0x1c)
[  441.374907]  r5:00000000 r4:20070193
[  441.378525] [] (dump_stack) from [] (nmi_cpu_backtrace+0xe0/0x114)
[  441.386424] [] (nmi_cpu_backtrace) from [] (nmi_trigger_cpumask_backtrace+0xe8/0x134)
[  441.395965]  r7:c010edfc r6:c0e01ee4 r5:c170469c r4:00000000
[  441.401597] [] (nmi_trigger_cpumask_backtrace) from [] (arch_trigger_cpumask_backtrace+0x20/0x24)
[  441.412180]  r9:c1703f10 r8:c0e01ee0 r7:c1835438 r6:00000000 r5:c1703fa4 r4:c171e840
[  441.419886] [] (arch_trigger_cpumask_backtrace) from [] (rcu_dump_cpu_stacks+0x144/0x174)
[  441.429922] [] (rcu_dump_cpu_stacks) from [] (rcu_sched_clock_irq+0x6a8/0xa58)
[  441.438860]  r10:2e138000 r9:c1702d00 r8:c1693f40 r7:c18361a0 r6:00000000 r5:ef7cbf40
[  441.446784]  r4:c171e840
[  441.449304] [] (rcu_sched_clock_irq) from [] (update_process_times+0x98/0xc4)
[  441.458174]  r10:c1702d80 r9:c1702d40 r8:c184fd40 r7:2e138000 r6:c1702d00 r5:00000000
[  441.465969]  r4:ef7c5540
[  441.468524] [] (update_process_times) from [] (tick_sched_timer+0x88/0x2d8)
[  441.477198]  r7:c1ea9dc0 r6:00000066 r5:bf87a4da r4:ef7c6128
[  441.482830] [] (tick_sched_timer) from [] (__hrtimer_run_queues+0x1fc/0x36c)
[  441.491730]  r10:ef7c5e14 r9:ef7c6128 r8:20070193 r7:00000000 r6:c01b7458 r5:ef7c5dc0
[  441.499645]  r4:ef7c5e00
[  441.502183] [] (__hrtimer_run_queues) from [] (hrtimer_interrupt+0x13c/0x2c8)
[  441.511041]  r10:ef7c5e98 r9:ef7c5e70 r8:ef7c5e48 r7:ef7c5dcc r6:00000003 r5:20070193
[  441.518836]  r4:ef7c5dc0
[  441.521357] [] (hrtimer_interrupt) from [] (twd_handler+0x44/0x4c)
[  441.529394]  r10:c1ea8000 r9:c1ea9dc0 r8:f080210c r7:c1d08240 r6:00000018 r5:c17046b4
[  441.537301]  r4:00000001
[  441.539821] [] (twd_handler) from [] (handle_percpu_devid_irq+0x9c/0x200)
[  441.548321]  r5:c17046b4 r4:c1d09000
[  441.551888] [] (handle_percpu_devid_irq) from [] (handle_domain_irq+0x6c/0x88)
[  441.560961]  r7:0000001d r6:00000000 r5:00000000 r4:c1692a14
[  441.566593] [] (handle_domain_irq) from [] (gic_handle_irq+0x88/0x9c)
[  441.574767]  r7:c1692a20 r6:f0802100 r5:c177a344 r4:c17046b4
[  441.580494] [] (gic_handle_irq) from [] (__irq_svc+0x5c/0x78)
[  441.587952] Exception stack(0xc1ea9dc0 to 0xc1ea9e08)
[  441.593047] 9dc0: c28b3700 00000000 00000000 00000003 00001000 c28b3700 c2b47f40 befe9c04
[  441.601193] 9de0: c28b3774 befe9c04 c1ea8000 c1ea9e24 c1ea9e28 c1ea9e10 c0a95530 c0a949ac
[  441.609342] 9e00: 20070013 ffffffff
[  441.612863]  r9:c1ea8000 r8:c28b3774 r7:c1ea9df4 r6:ffffffff r5:20070013 r4:c0a949ac
[  441.620699] [] (iio_dma_buffer_dequeue) from [] (iio_dma_buffer_read+0x148/0x19c)
[  441.629894]  r5:c28b3700 r4:00001000
[  441.633452] [] (iio_dma_buffer_read) from [] (iio_buffer_read+0x178/0x228)
[  441.642168]  r10:c1ea8000 r9:befe9c04 r8:00001000 r7:00000400 r6:00000002 r5:c1e43000
[  441.649962]  r4:c28b3700
[  441.652483] [] (iio_buffer_read) from [] (iio_buffer_read_wrapper+0x2c/0x38)
[  441.661248]  r10:00000003 r9:c0954af8 r8:00001000 r7:00000001 r6:c1ea8000 r5:c1ea9f60
[  441.669050]  r4:c2b28540
[  441.671571] [] (iio_buffer_read_wrapper) from [] (vfs_read+0xc4/0x320)
[  441.679817] [] (vfs_read) from [] (ksys_read+0x74/0xec)
[  441.686766]  r10:00000003 r9:00000000 r8:00000000 r7:befe9c04 r6:c1ea8000 r5:c2b28540
[  441.694560]  r4:c2b28540
[  441.697081] [] (ksys_read) from [] (sys_read+0x18/0x1c)
[  441.704027]  r9:c1ea8000 r8:c0100244 r7:00000003 r6:b6f681a0 r5:befe9c04 r4:00001000
[  441.711733] [] (sys_read) from [] (ret_fast_syscall+0x0/0x48)
[  441.719310] Exception stack(0xc1ea9fa8 to 0xc1ea9ff0)
[  441.724344] 9fa0:                   00001000 befe9c04 00000003 befe9c04 00001000 00000000
[  441.732488] 9fc0: 00001000 befe9c04 b6f681a0 00000003 00000000 01000000 00000003 befe9c04
[  441.740769] 9fe0: 00000003 befe9bb8 b6e6070f b6de1ae6

and that output repeats every ~20 seconds. The device is supposed to send an interrupt to the OS when the buffer is ready, so I probed the DRDY pin (which is the pin for the interrupt) of the device with an MCU, and the pin never goes high. I also tried switching the libiio version I was using to the same as the evaluation image, 0.23 to 0.21 and the error when running iio_readdev ad7768-1 changed from Unable to refill buffer: Connection timed out (110) to

Unable to refill buffer: Connection timed out
ERROR: Error during buffer disable: No such file or directory

which I'm pretty sure is functionally the same error, so I changed the libiio version back to 0.23 I patched the device driver and libiio in an attempt to find the problem and found out that the problem line from calling iio_readdev ad7768-1 in libiio is this one ret = poll(pollfd, 2, timeout_rel);, and the problem function in the device driver seems to be this one hw_submit_block. What is causing the timed out error?

I have a BeagleBone green and ADT7516's evaluation board connected with SDA and SCL pins. When I do i2cdetect -y -r 2, I can see the i2c address as 0x4b and I am able to probe the adt7316 driver present in IIO subsystem. adt7316 driver uses platform data to get the hardware description. But my goal is to remove platform data and use DT bindings. I understand some basic things about the DT bindings like.. 1. Compatible 2. reg But when I have a close look at the driver, I can see that there are certain things which are taken from the platform data and are used in the whole driver. So my question is that how do I replace those things in the driver if I remove platform data and use DT bindings. I am putting probe function's code here. int adt7316_probe(struct device *dev, struct adt7316_bus *bus, const char *name) { struct adt7316_chip_info *chip; struct iio_dev *indio_dev; unsigned short *adt7316_platform_data = dev->platform_data; int ret = 0; indio_dev = devm_iio_device_alloc(dev, sizeof(*chip)); if (!indio_dev) return -ENOMEM; chip = iio_priv(indio_dev); /* this is only used for device removal purposes */ dev_set_drvdata(dev, indio_dev); chip->bus = *bus; if (name == '3') chip->id = ID_ADT7316 + (name - '6'); else if (name == '5') chip->id = ID_ADT7516 + (name - '6'); else return -ENODEV; chip->ldac_pin = adt7316_platform_data; if (chip->ldac_pin) { chip->config3 |= ADT7316_DA_EN_VIA_DAC_LDCA; if ((chip->id & ID_FAMILY_MASK) == ID_ADT75XX) chip->config1 |= ADT7516_SEL_AIN3; } chip->int_mask = ADT7316_TEMP_INT_MASK | ADT7316_VDD_INT_MASK; if ((chip->id & ID_FAMILY_MASK) == ID_ADT75XX) chip->int_mask |= ADT7516_AIN_INT_MASK; indio_dev->dev.parent = dev; if ((chip->id & ID_FAMILY_MASK) == ID_ADT75XX) indio_dev->info = &adt7516_info; else indio_dev->info = &adt7316_info; indio_dev->name = name; indio_dev->modes = INDIO_DIRECT_MODE; if (chip->bus.irq > 0) { if (adt7316_platform_data) chip->bus.irq_flags = adt7316_platform_data; ret = devm_request_threaded_irq(dev, chip->bus.irq, NULL, adt7316_event_handler, chip->bus.irq_flags | IRQF_ONESHOT, indio_dev->name, indio_dev); if (ret) return ret; if (chip->bus.irq_flags & IRQF_TRIGGER_HIGH) chip->config1 |= ADT7316_INT_POLARITY; } ret = chip->bus.write(chip->bus.client, ADT7316_CONFIG1, chip->config1); if (ret) return -EIO; ret = chip->bus.write(chip->bus.client, ADT7316_CONFIG3, chip->config3); if (ret) return -EIO; ret = devm_iio_device_register(dev, indio_dev); if (ret) return ret; dev_info(dev, "%s temperature sensor, ADC and DAC registered.\n", indio_dev->name); return 0; } EXPORT_SYMBOL(adt7316_probe); So in the code we can see that **chip->ldac_pin** and **chip->bus.irq_flags** uses platform data. If I use DT bindings then platform data will have NULL value in it. So how do I design my DT bindings here and how can I fetch that data in the driver? I have seen many examples of DT bindings but I need specific help with adt7516 sensor. **Datasheet of adt7516 sensor** http://www.analog.com/media/en/technical-documentation/data-sheets/ADT7516_7517_7519.pdf

I have used a device tree overlay file (dtbo) to add a hardware reference over the i2c-2 node to my device tree. This device is an accelerometer that implements an existing driver that can be found here: https://elixir.bootlin.com/linux/v4.19.94/source/drivers/iio/accel/mma8452.c My device appears as iio:device0 in the /dev directory:

debian@beaglebone:/dev$ ls
accel            log                 spi        tty27  tty53     urandom
apm_bios         loop-control        spidev1.0  tty28  tty54     vcs
autofs           mapper              spidev1.1  tty29  tty55     vcs1
block            mem                 spidev2.0  tty3   tty56     vcs2
btrfs-control    memory_bandwidth    spidev2.1  tty30  tty57     vcs3
bus              mmcblk0             stderr     tty31  tty58     vcs4
char             mmcblk0p1           stdin      tty32  tty59     vcs5
console          mmcblk1             stdout     tty33  tty6      vcs6
cpu_dma_latency  mmcblk1boot0        tty        tty34  tty60     vcsa
cuse             mmcblk1boot1        tty0       tty35  tty61     vcsa1
disk             mmcblk1p1           tty1       tty36  tty62     vcsa2
dri              mmcblk1rpmb         tty10      tty37  tty63     vcsa3
fb0              mqueue              tty11      tty38  tty7      vcsa4
fd               net                 tty12      tty39  tty8      vcsa5
full             network_latency     tty13      tty4   tty9      vcsa6
fuse             network_throughput  tty14      tty40  ttyGS0    vcsu
gpiochip0        null                tty15      tty41  ttyO0     vcsu1
gpiochip1        ppp                 tty16      tty42  ttyO1     vcsu2
gpiochip2        ptmx                tty17      tty43  ttyO2     vcsu3
gpiochip3        pts                 tty18      tty44  ttyO4     vcsu4
hwrng            pwm                 tty19      tty45  ttyO5     vcsu5
i2c-0            random              tty2       tty46  ttyS0     vcsu6
i2c-1            remoteproc          tty20      tty47  ttyS1     vhci
i2c-2            rfkill              tty21      tty48  ttyS2     watchdog
iio:device0      rtc                 tty22      tty49  ttyS4     watchdog0
initctl          rtc0                tty23      tty5   ttyS5     watchdog1
input            shm                 tty24      tty50  ubi_ctrl  zero
ion              snapshot            tty25      tty51  uhid
kmsg             snd                 tty26      tty52  uinput

My device can also be viewed in:

debian@beaglebone:/sys/class/i2c-dev/i2c-2/subsystem/i2c-2/device/2-001c$ ls
driver       modalias  of_node  subsystem  uevent
iio:device0  name      power    trigger0

Here you can see the specifics of the device naming:

debian@beaglebone:/sys/class/i2c-dev/i2c-2/subsystem/i2c-2/device/2-001c/iio:device0$ cat uevent
MAJOR=248
MINOR=0
DEVNAME=iio:device0
DEVTYPE=iio_device
OF_NAME=accelerometer
OF_FULLNAME=/ocp/i2c@4819c000/accelerometer@1C
OF_COMPATIBLE_0=fsl,mma8451
OF_COMPATIBLE_N=1

**My question is, where does this device get its name as iio:device0?** I assume this is simply a default name as I haven't specified one. **My question therefore becomes: How do I specify a name for my device in the device tree? It seems I would like to change the DEVNAME somehow.** I do not see any reason for this name in my dtbo file, which can be seen below:

/*
 * MIRA custom cape device tree overlay
 * Supports MMA8451Q Accelerometer  
 */
/dts-v1/;
/plugin/;

#include 

/ {
        /*
         * Helper to show loaded overlays under: /proc/device-tree/chosen/overlays/
         */
        fragment@0 {
                target-path="/";
                __overlay__ {

                        chosen {
                                overlays {
                                        MIRA_EXTENSIONS = __TIMESTAMP__;
                                };
                        };
                };
        };

        fragment@1 {
                target = ;

                __overlay__ {
                        status = "okay";
                        #address-cells = ;
                        #size-cells = ;
                        accelerometer@1C {
                                compatible = "fsl,mma8451";
                                reg = ;
                                interrupt-parent = ;
                                interrupts = ;
                                interrupt-names = "INT1";
                        };
                };
        };
};

I am using the Aria G25 board from Acme Systems. I have their Terra board breakout. I have also asked this question on their google groups but thought it might be a more general issue so have posted here as well. I have built the ADC into the kernel (not as module) based on this guide: http://www.at91.com/linux4sam/bin/view/Linux4SAM/IioAdcDriver At startup I am able to grep for iio and get: root@acmeboard:~# dmesg | grep iio iio iio:device0: Resolution used: 10 bits iio iio:device0: ADC Touch screen is disabled. After startup I have the appropriate sysfs structure: root@acmeboard:~# ls -l /sys/bus/iio/devices/iio\:device0/ total 0 drwxr-xr-x 2 root root 0 Jan 1 01:06 buffer -r--r--r-- 1 root root 4096 Jan 1 01:06 dev -rw-r--r-- 1 root root 4096 Jan 1 01:01 in_voltage0_raw -rw-r--r-- 1 root root 4096 Jan 1 01:01 in_voltage1_raw -rw-r--r-- 1 root root 4096 Jan 1 01:01 in_voltage2_raw -rw-r--r-- 1 root root 4096 Jan 1 01:01 in_voltage3_raw -rw-r--r-- 1 root root 4096 Jan 1 01:06 in_voltage_scale -r--r--r-- 1 root root 4096 Jan 1 01:06 name drwxr-xr-x 2 root root 0 Jan 1 01:06 power drwxr-xr-x 2 root root 0 Jan 1 01:06 scan_elements lrwxrwxrwx 1 root root 0 Jan 1 01:06 subsystem -> ../../../../../bus/iio drwxr-xr-x 2 root root 0 Jan 1 01:06 trigger -rw-r--r-- 1 root root 4096 Jan 1 01:06 uevent However when attempting to read the ADC value I always get 1023 (I have a potentiometer connected on one of their breakout boards, so I would expect to not read the max): root@acmeboard:~# cat /sys/bus/iio/devices/iio\:device0/in_voltage0_raw 1023 I am relatively new to linux and sysfs so I could be missing something simple. Other point of interest. If I read the same pin (W20 on Aria) as a digital GPIO it appears to work. Spinning the pot I eventually read 0 and then 1 going the other way. Do I some how need to disable the GPIO functionality for this pin? Finally here is the relevant lines in the DTS file (only thing I've changed): adc0: adc@f804c000 { status = "okay"; atmel,adc-channels-used = ; atmel,adc-num-channels = ; compatible = "atmel,at91sam9x5-adc"; atmel,adc-startup-time = ; atmel,adc-status-register = ; atmel,adc-trigger-register = ; atmel,adc-use-external; atmel,adc-vref = ; atmel,adc-res = ; atmel,adc-res-names = "lowres", "highres"; atmel,adc-use-res = "highres"; trigger@0 { trigger-name = "continuous"; trigger-value = ; }; };

I have a tablet with builtin sensors which allow me automatic screen rotation, based on iio-sensors-proxy. However, the screen orientation is off, and I need to fix it. On it's GitHub page (https://github.com/systemd/systemd/blob/master/hwdb/60-sensor.hwdb) is explained how to change this behavior: Create a file /etc/udev/hwdb.d/61-sensor-local.hwdb and write to it sensor:modalias::dmi: and ACCEL_MOUNT_MATRIX=1, 0, 0; 0, 1, 0; 0, 0, 1 (this matrix has to be changed ofc). # Problem : I have no idea how to get the neccessary information for the first line, the sensor-prefix. # Solution : Final file contains: sensor:modalias:acpi:KIOX000A*:dmi:*:svnEVE*:pnEveV:* ACCEL_MOUNT_MATRIX=0, 1, 0; -1, 0, 0; 0, 0, 1 What I've found so far: This gives me device name: udevadm info --export-db | grep iio P: /devices/pci0000:00/0000:00:15.0/i2c_designware.0/i2c-0/i2c-KIOX000A:00/iio:device0 N: iio:device0 E: DEVNAME=/dev/iio:device0 E: DEVPATH=/devices/pci0000:00/0000:00:15.0/i2c_designware.0/i2c-0/i2c-KIOX000A:00/iio:device0 E: DEVTYPE=iio_device E: IIO_SENSOR_PROXY_TYPE=iio-buffer-accel E: SUBSYSTEM=iio E: SYSTEMD_WANTS=iio-sensor-proxy.service This gives me more info about the device: udevadm info -n "/dev/iio:device0" P: /devices/pci0000:00/0000:00:15.0/i2c_designware.0/i2c-0/i2c-KIOX000A:00/iio:device0 N: iio:device0 E: DEVNAME=/dev/iio:device0 E: DEVPATH=/devices/pci0000:00/0000:00:15.0/i2c_designware.0/i2c-0/i2c-KIOX000A:00/iio:device0 E: DEVTYPE=iio_device E: IIO_SENSOR_PROXY_TYPE=iio-buffer-accel E: MAJOR=245 E: MINOR=0 E: SUBSYSTEM=iio E: SYSTEMD_WANTS=iio-sensor-proxy.service E: TAGS=:systemd: E: USEC_INITIALIZED=1959744 And via pci I find the so-called modalias: cat /sys/devices/pci0000:00/0000:00:15.0/modalias pci:v00008086d00009D60sv00008086sd00007270bc11sc80i00 Would really appreciate help from here on! --- My system: Linux jva 4.14.5-1-ARCH #1 SMP PREEMPT Sun Dec 10 14:50:30 UTC 2017 x86_64 GNU/Linux running under GNOME 3.26.2 (Wayland-seesion) Tablet: Eve V i7Y

The driver I'm developing has a number of settings I want the user to be able to change that don't really fit into the IIO framework. For example, using the IIO_CHAN_INFO_SAMP_FREQ enum in my read function exposes a variable in /sys/bus/iio/devices/iio:device0/ called "in_voltage_sampling_frequency" that allows the user to change the frequency on-the-go. I would also like to be able to pass in different modes (a string) through a similar mechanism. How would I do this? It doesn't look like the IIO interface supports ioctl calls. So in short, what I want is a mechanism to expose a variable called "timer_mode" through IIO, that people could pass a string into that my driver can use.

I am trying to read one sample from a sensor using libiio, but for some reason I always get the same sample unless I restart the application. Here is a minimal example

#include 
#include 
#include 
#include 
#include 


/* Global objects */
static struct iio_buffer *device_buffer = NULL;
static struct iio_channel *channel = NULL;
static struct iio_context *local_ctx = NULL;
static struct iio_device *dev = NULL;
static const char *dev_name = NULL;
static const char *channel_id = NULL;
static uint8_t *in_buf;


int main()
{

        /* Getting local iio device context */
        local_ctx = iio_create_local_context();
        dev = iio_context_get_device(local_ctx, 0);
        dev_name = iio_device_get_name(dev);
        channel = iio_device_get_channel(dev, 0);

        iio_channel_enable(channel);
        if (iio_channel_is_enabled(channel))
                return -1;

        uint32_t sample_size = 3;
        uint32_t buffer_length = 1;

        struct iio_buffer *device_buffer =
                iio_device_create_buffer(dev, buffer_length, false);

        if (!device_buffer)
                return -1;

        while (true) {
                ssize_t nbytes_rx = iio_buffer_refill(device_buffer);

                if (nbytes_rx <= 0) {
                        printf("Error refilling buf %d\n", (int) nbytes_rx);
                        return -1;
                }

                in_buf = (uint8_t*)malloc(sample_size * buffer_length);
                iio_channel_read(channel, device_buffer, in_buf, sample_size * buffer_length);
                printf("%" PRIi32 "\n", ((int32_t *)in_buf));
                free(in_buf);

        }
}

In the actual code I am properly error checking, handling SIGINT and destroying all the buffers. Everything works. The only issue is that the same sample is printed over and over, whereas I would assume the buffer to get refilled and a new sample to get printed.