Hello,
I find an "adc" device by the following code:
*struct device dev;*
*static int custom_match_dev(struct device *dev, const void *data)*
*{ // this function implements the comaparison logic. Return not zero if
found. const char *name = data; int result = 0;*
* if (dev == NULL)*
* return result; if (dev->of_node == NULL) return
result; if (dev->of_node->name == NULL) return result;*
* result = sysfs_streq(name, dev->of_node->name);*
* return result;}static struct device *find_dev(const char *name){
struct device *dev = NULL; dev = bus_find_device(&platform_bus_type,
NULL, name, custom_match_dev); return dev;*
*}*
and there is an "adc" here:
~#
*cat /sys/bus/platform/devices/TI-am335x-adc.2.auto/of_node/nameadc*
*~# ls
/sys/bus/platform/devices/TI-am335x-adc.2.auto/of_node/#io-channel-cells
compatible name ti,adc-channels*
*~# ls /sys/bus/platform/devices/TI-am335x-adc.2.autodriver
iio:device0 of_node subsystemdriver_override
modalias power uevent*
*~# ls /sys/bus/iio/devices/iio\:device0/buffer/ in_voltage2_raw
in_voltage6_raw power/dev in_voltage3_raw in_voltage7_raw
scan_elements/in_voltage0_raw in_voltage4_raw name
subsystem/in_voltage1_raw in_voltage5_raw of_node/ uevent*
When I try to get the iio channels with *devm_IIo_channel_get *or*
devm_IIo_channel_get_all. *I always get -19 answer (no such device). I also
tried the *iio_channel_get *and* iio_channel_get_all *and the result is
same.
*struct iio_channel *channels;channels = iio_channel_get(dev,
"iio:device0"); if (IS_ERR(channels)) { printk(KERN_ERR
"channels: %d\n", (int)channels); //return 0; return
PTR_ERR(channels); }*
At the iio_channel_get second parameter I tried various stings like channel
number and other strings I found under /sys/bus/iio.... and path above.
What is wrong with this code?
Please give me any advice how I read adc channels in kernel space.
Thank you in advance.
Roland Dobak
droland a következőt írta (2021. február 25., csütörtök, 13:17:22 UTC+1):
>
> Hello,
>
> I can read/write gpio pins from the kernel module, but now I should
> read/access ADC channels from the kernel modules.
> I found some examples, but each uses file access with the open / read /
> close commands. they work well in user space but not in kernel space.
> Some sample code uses sysfs_open with changing code segment (KERNEL_DS)
> (Unfortunately) I could not compile my module because the sysfs commands
> were not exported in Linux source and I think the file operations is not a
> good idea in kernel space.
>
> I'm working on a custom build Linux with 5.4 kernel on Beaglebone Black.
> Thanks to some articles by Derek Molloy, I can access to gpio, but I got
> stuck at the ADC (iio).
> (I see and I can read the
> /sys/bus/iio/devices/iio\:device0/in_voltageX_raw and in user space works
> fine.)
>
> What is the correct mode or how can I read ADC channels from the kernel
> space/module (without segment manipulation)?
> (I'm also interested in using the UART in kernel module...)
>
> Please, anyone help me with any useful information.
>
> Thank you in advance.
>
> Roland Dobak
>
>
>
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