Hi Roland,
I am not sure that I completely understand your question but have you
looked at the iio_generic_buffer
(https://github.com/torvalds/linux/blob/master/tools/iio/iio_generic_buffer.c)?
I did something similar 3 years ago and used this example to sample the BBB
ADC using the iio driver and read the results in userspace after.
Sorry if I am way off the mark here.
Best
Pierrick
Le lundi 8 mars 2021 à 10:21:03 UTC-5, droland a écrit :
> 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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