"Device or resource busy" when attempting to add a third buffer with iio_device_create_buffer to ad9361-iiostream.c example code

Hello-

I am  modifying the ad9361-iiostream.c https://github.com/analogdevicesinc/libiio/blob/master/examples/ad9361-iiostream.c example as a simple experiment to create a third iio buffer.

I have no competing applications such as iio-oscilloscope using the resources, but console output shows that it  "Could not create RF buffer: Device or resource busy" on the first attempt to run the code.

In this thread, https://ez.analog.com/linux-device-drivers/linux-software-drivers/f/q-a/87769/libiio-device-or-resource-busy-when-creating-buffers/313187#313187 mahkoe seems to have successfully created the buffers , but can't open them after running another program that uses the resources.. I cant create them at all even though it is the only program I run, not even the first time after a fresh boot from power off of target and host.. I am using zc702 and FMCOMMS2.

Console output below:

root@analog:~/tmp# ./ad9361-iiostream
* Acquiring IIO context
* Acquiring AD9361 streaming devices
* Configuring AD9361 for streaming
* Acquiring AD9361 phy channel 0
* Acquiring AD9361 RX lo channel
* Acquiring AD9361 phy channel 0
* Acquiring AD9361 TX lo channel
* Initializing AD9361 IIO streaming channels
* Enabling IIO streaming channels
* Creating non-cyclic IIO buffers with 1 MiS
* Receive buffer created
* Transmit buffer created
Could not create RF buffer: Device or resource busy
* Destroying buffers
* Disabling streaming channels
* Destroying context

It seems straightforward and common to create multiple buffers, can anyone see what the issue is here? I appreciate your suggestions.

I've attached my code and anything that I thought should be modified to create the third buffer (which I call RF) is commented with //RF or /*RF*/

Full modified code is copied below:

/*
* libiio - AD9361 IIO streaming example
*
* Copyright (C) 2014 IABG mbH
* Author: Michael Feilen <feilen_at_iabg.de>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
**/

#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <signal.h>
#include <stdio.h>

#ifdef __APPLE__
#include <iio/iio.h>
#else
#include <iio.h>
#endif

/* helper macros */
#define MHZ(x) ((long long)(x*1000000.0 + .5))
#define GHZ(x) ((long long)(x*1000000000.0 + .5))

#define ASSERT(expr) { \
if (!(expr)) { \
(void) fprintf(stderr, "assertion failed (%s:%d)\n", __FILE__, __LINE__); \
(void) abort(); \
} \
}

/* RX is input, TX is output */
enum iodev { RX, TX };

/* common RX and TX streaming params */
struct stream_cfg {
long long bw_hz; // Analog banwidth in Hz
long long fs_hz; // Baseband sample rate in Hz
long long lo_hz; // Local oscillator frequency in Hz
const char* rfport; // Port name
};

/* static scratch mem for strings */
static char tmpstr[64];

/* IIO structs required for streaming */
static struct iio_context *ctx = NULL;
static struct iio_channel *rx0_i = NULL;
static struct iio_channel *rx0_q = NULL;
static struct iio_channel *tx0_i = NULL;
static struct iio_channel *tx0_q = NULL;
static struct iio_channel *rf0_i = NULL; //RF
static struct iio_channel *rf0_q = NULL; //RF

static struct iio_buffer *rxbuf = NULL;
static struct iio_buffer *txbuf = NULL;

static struct iio_buffer *rfbuf = NULL; /*RF*/

static bool stop;

/* cleanup and exit */
static void shutdown()
{
printf("* Destroying buffers\n");
if (rxbuf) { iio_buffer_destroy(rxbuf); }
if (txbuf) { iio_buffer_destroy(txbuf); }
if (rfbuf) { iio_buffer_destroy(rfbuf); } /*RF*/

printf("* Disabling streaming channels\n");
if (rx0_i) { iio_channel_disable(rx0_i); }
if (rx0_q) { iio_channel_disable(rx0_q); }
if (tx0_i) { iio_channel_disable(tx0_i); }
if (tx0_q) { iio_channel_disable(tx0_q); }
if (rf0_i) { iio_channel_disable(rf0_i); } //RF
if (rf0_q) { iio_channel_disable(rf0_q); } //RF

printf("* Destroying context\n");
if (ctx) { iio_context_destroy(ctx); }
exit(0);
}

static void handle_sig(int sig)
{
printf("Waiting for process to finish...\n");
stop = true;
}

/* check return value of attr_write function */
static void errchk(int v, const char* what) {
if (v < 0) { fprintf(stderr, "Error %d writing to channel \"%s\"\nvalue may not be supported.\n", v, what); shutdown(); }
}

/* write attribute: long long int */
static void wr_ch_lli(struct iio_channel *chn, const char* what, long long val)
{
errchk(iio_channel_attr_write_longlong(chn, what, val), what);
}

/* write attribute: string */
static void wr_ch_str(struct iio_channel *chn, const char* what, const char* str)
{
errchk(iio_channel_attr_write(chn, what, str), what);
}

/* helper function generating channel names */
static char* get_ch_name(const char* type, int id)
{
snprintf(tmpstr, sizeof(tmpstr), "%s%d", type, id);
return tmpstr;
}

/* returns ad9361 phy device */
static struct iio_device* get_ad9361_phy(struct iio_context *ctx)
{
struct iio_device *dev = iio_context_find_device(ctx, "ad9361-phy");
ASSERT(dev && "No ad9361-phy found");
return dev;
}

/* finds AD9361 streaming IIO devices */
static bool get_ad9361_stream_dev(struct iio_context *ctx, enum iodev d, struct iio_device **dev)
{
switch (d) {
case TX: *dev = iio_context_find_device(ctx, "cf-ad9361-dds-core-lpc"); return *dev != NULL;
case RX: *dev = iio_context_find_device(ctx, "cf-ad9361-lpc"); return *dev != NULL;
default: ASSERT(0); return false;
}
}

/* finds AD9361 streaming IIO channels */
static bool get_ad9361_stream_ch(struct iio_context *ctx, enum iodev d, struct iio_device *dev, int chid, struct iio_channel **chn)
{
*chn = iio_device_find_channel(dev, get_ch_name("voltage", chid), d == TX);
if (!*chn)
*chn = iio_device_find_channel(dev, get_ch_name("altvoltage", chid), d == TX);
return *chn != NULL;
}

/* finds AD9361 phy IIO configuration channel with id chid */
static bool get_phy_chan(struct iio_context *ctx, enum iodev d, int chid, struct iio_channel **chn)
{
switch (d) {
case RX: *chn = iio_device_find_channel(get_ad9361_phy(ctx), get_ch_name("voltage", chid), false); return *chn != NULL;
case TX: *chn = iio_device_find_channel(get_ad9361_phy(ctx), get_ch_name("voltage", chid), true); return *chn != NULL;
default: ASSERT(0); return false;
}
}

/* finds AD9361 local oscillator IIO configuration channels */
static bool get_lo_chan(struct iio_context *ctx, enum iodev d, struct iio_channel **chn)
{
switch (d) {
// LO chan is always output, i.e. true
case RX: *chn = iio_device_find_channel(get_ad9361_phy(ctx), get_ch_name("altvoltage", 0), true); return *chn != NULL;
case TX: *chn = iio_device_find_channel(get_ad9361_phy(ctx), get_ch_name("altvoltage", 1), true); return *chn != NULL;
default: ASSERT(0); return false;
}
}

/* applies streaming configuration through IIO */
bool cfg_ad9361_streaming_ch(struct iio_context *ctx, struct stream_cfg *cfg, enum iodev type, int chid)
{
struct iio_channel *chn = NULL;

// Configure phy and lo channels
printf("* Acquiring AD9361 phy channel %d\n", chid);
if (!get_phy_chan(ctx, type, chid, &chn)) { return false; }
wr_ch_str(chn, "rf_port_select", cfg->rfport);
wr_ch_lli(chn, "rf_bandwidth", cfg->bw_hz);
wr_ch_lli(chn, "sampling_frequency", cfg->fs_hz);

// Configure LO channel
printf("* Acquiring AD9361 %s lo channel\n", type == TX ? "TX" : "RX");
if (!get_lo_chan(ctx, type, &chn)) { return false; }
wr_ch_lli(chn, "frequency", cfg->lo_hz);
return true;
}

/* simple configuration and streaming */
int main (int argc, char **argv)
{
// Streaming devices
struct iio_device *tx;
struct iio_device *rx;
struct iio_device *rf; /*RF */

// RX and TX sample counters
size_t nrx = 0;
size_t ntx = 0;
size_t nrf = 0; /*RF */

// Stream configurations
struct stream_cfg rxcfg;
struct stream_cfg txcfg;
struct stream_cfg rfcfg;

// Listen to ctrl+c and ASSERT
signal(SIGINT, handle_sig);

// RX stream config
rxcfg.bw_hz = MHZ(2); // 2 MHz rf bandwidth
rxcfg.fs_hz = MHZ(2.5); // 2.5 MS/s rx sample rate
rxcfg.lo_hz = GHZ(2.5); // 2.5 GHz rf frequency
rxcfg.rfport = "A_BALANCED"; // port A (select for rf freq.)

// TX stream config
txcfg.bw_hz = MHZ(1.5); // 1.5 MHz rf bandwidth
txcfg.fs_hz = MHZ(2.5); // 2.5 MS/s tx sample rate
txcfg.lo_hz = GHZ(2.5); // 2.5 GHz rf frequency
txcfg.rfport = "A"; // port A (select for rf freq.)

printf("* Acquiring IIO context\n");
ASSERT((ctx = iio_create_default_context()) && "No context");
ASSERT(iio_context_get_devices_count(ctx) > 0 && "No devices");

printf("* Acquiring AD9361 streaming devices\n");
ASSERT(get_ad9361_stream_dev(ctx, TX, &tx) && "No tx dev found");
ASSERT(get_ad9361_stream_dev(ctx, RX, &rx) && "No rx dev found");
ASSERT(get_ad9361_stream_dev(ctx, RX, &rf) && "No rf dev found"); //RF

printf("* Configuring AD9361 for streaming\n");
ASSERT(cfg_ad9361_streaming_ch(ctx, &rxcfg, RX, 0) && "RX port 0 not found");
ASSERT(cfg_ad9361_streaming_ch(ctx, &txcfg, TX, 0) && "TX port 0 not found");
//ASSERT(cfg_ad9361_streaming_ch(ctx, &rfcfg, RX, 0) && "RF port 0 not found"); // RF


printf("* Initializing AD9361 IIO streaming channels\n");
ASSERT(get_ad9361_stream_ch(ctx, RX, rx, 0, &rx0_i) && "RX chan i not found");
ASSERT(get_ad9361_stream_ch(ctx, RX, rx, 1, &rx0_q) && "RX chan q not found");
ASSERT(get_ad9361_stream_ch(ctx, TX, tx, 0, &tx0_i) && "TX chan i not found");
ASSERT(get_ad9361_stream_ch(ctx, TX, tx, 1, &tx0_q) && "TX chan q not found");
ASSERT(get_ad9361_stream_ch(ctx, RX, rf, 0, &rf0_i) && "RX chan i not found"); //RF
ASSERT(get_ad9361_stream_ch(ctx, RX, rf, 1, &rf0_q) && "RX chan q not found"); //RF

printf("* Enabling IIO streaming channels\n");
iio_channel_enable(rx0_i);
iio_channel_enable(rx0_q);
iio_channel_enable(tx0_i);
iio_channel_enable(tx0_q);
iio_channel_enable(rf0_i); //RF
iio_channel_enable(rf0_q); //RF

printf("* Creating non-cyclic IIO buffers with 1 MiS\n");

rxbuf = iio_device_create_buffer(rx, 1024, false);//RF reduce size by *1024
if (!rxbuf) {
perror("Could not create RX buffer");
shutdown();
}

printf("* Receive buffer created\n");





txbuf = iio_device_create_buffer(tx, 1024, false); //RF reduce size by *1024
if (!txbuf) {
perror("Could not create TX buffer");
shutdown();
}

printf("* Transmit buffer created\n");




//RF trouble using rx device
rfbuf = iio_device_create_buffer(rx, 1024, false);
if (!rfbuf) {
perror("Could not create RF buffer");
shutdown();
}

printf("* Aux buffer created\n");

printf("* Starting IO streaming (press CTRL+C to cancel)\n");
while (!stop)
{
ssize_t nbytes_rx, nbytes_tx, nbytes_rf;
char *p_dat, *p_end;
ptrdiff_t p_inc;

// Schedule TX buffer
nbytes_tx = iio_buffer_push(txbuf);
if (nbytes_tx < 0) { printf("Error pushing buf %d\n", (int) nbytes_tx); shutdown(); }

// Refill RX buffer
nbytes_rx = iio_buffer_refill(rxbuf);
if (nbytes_rx < 0) { printf("Error refilling buf %d\n",(int) nbytes_rx); shutdown(); }

/* Refill RF buffer
nbytes_rf = iio_buffer_refill(rfbuf);
if (nbytes_rf < 0) { printf("Error refilling buf %d\n",(int) nbytes_rf); shutdown(); }
*/

printf("* round 2\n");

// READ: Get pointers to RX buf and read IQ from RX buf port 0
p_inc = iio_buffer_step(rxbuf);
p_end = iio_buffer_end(rxbuf);
for (p_dat = (char *)iio_buffer_first(rxbuf, rx0_i); p_dat < p_end; p_dat += p_inc) {
// Example: swap I and Q
const int16_t i = ((int16_t*)p_dat)[0]; // Real (I)
const int16_t q = ((int16_t*)p_dat)[1]; // Imag (Q)
((int16_t*)p_dat)[0] = q;
((int16_t*)p_dat)[1] = i;
}

// WRITE: Get pointers to TX buf and write IQ to TX buf port 0
p_inc = iio_buffer_step(txbuf);
p_end = iio_buffer_end(txbuf);
for (p_dat = (char *)iio_buffer_first(txbuf, tx0_i); p_dat < p_end; p_dat += p_inc) {
// Example: fill with zeros
// 12-bit sample needs to be MSB alligned so shift by 4
// wiki.analog.com/.../basic_iq_datafiles
((int16_t*)p_dat)[0] = 0 << 4; // Real (I)
((int16_t*)p_dat)[1] = 0 << 4; // Imag (Q)
}

// Sample counter increment and status output
nrx += nbytes_rx / iio_device_get_sample_size(rx);
ntx += nbytes_tx / iio_device_get_sample_size(tx);

nrf += nbytes_rf / iio_device_get_sample_size(rf); //RF


printf("\tRX %8.2f MSmp, TX %8.2f MSmp\n, RF %8.2f MSmp\n", nrx/1e6, ntx/1e6, nrf/1e6);
}

shutdown();

return 0;
}