nrf_modem_lib: Add nrf_modem_lib_trace_peek_at() API

Add API to peek modem trace data from a specific offset.
Support for the API is added in the flash backend.

Signed-off-by: Jan Tore Guggedal <[email protected]>

Author: jtguggedal

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -652,6 +652,11 @@ Modem libraries
     * The order of the ``LTE_LC_MODEM_EVT_SEARCH_DONE`` modem event, and registration and cell related events.
       See the :ref:`migration guide <migration_3.2_required>` for more information.
 
+* :ref:`nrf_modem_lib_readme` library:
+
+  * Added the :c:func:`nrf_modem_lib_trace_peek_at` function to the :c:struct:`nrf_modem_lib_trace_backend` interface to peek trace data at a byte offset without consuming it.
+    Support for this API has been added to the flash trace backend.
+
 Multiprotocol Service Layer libraries
 -------------------------------------
 

include/modem/nrf_modem_lib_trace.h

@@ -103,6 +103,25 @@ int nrf_modem_lib_trace_read(uint8_t *buf, size_t len);
  */
 int nrf_modem_lib_trace_clear(void);
 
+/**
+ * @brief Peek trace data at offset without consuming it
+ *
+ * Copy up to @p len bytes starting at @p offset from the oldest available data into @p buf
+ * without advancing the backend read cursor.
+ *
+ * @param offset Byte offset relative to the oldest available byte
+ * @param buf Output buffer
+ * @param len Size of output buffer
+ *
+ * @return number of bytes copied, negative errno on failure.
+ * @retval -ENOTSUP if the operation is not supported by the trace backend.
+ * @retval -EPERM if the trace backend is not initialized.
+ * @retval -EINVAL if the buffer is NULL.
+ * @retval -EFAULT if the offset is beyond the available trace data.
+ * @retval -ENODATA if no data is available at the offset.
+ */
+int nrf_modem_lib_trace_peek_at(size_t offset, uint8_t *buf, size_t len);
+
 #if defined(CONFIG_NRF_MODEM_LIB_TRACE_BACKEND_BITRATE) || defined(__DOXYGEN__)
 /** @brief Get the last measured rolling average bitrate of the trace backend.
  *

include/modem/trace_backend.h

@@ -7,6 +7,8 @@
 #ifndef TRACE_BACKEND_H__
 #define TRACE_BACKEND_H__
 
+#include <zephyr/kernel.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -92,6 +94,22 @@ struct nrf_modem_lib_trace_backend {
 	 */
 	int (*read)(void *buf, size_t len);
 
+	/**
+	 * @brief Peek trace data at a byte offset without consuming it.
+	 *
+	 * Copy up to @p len bytes starting at @p offset from the beginning of the
+	 * currently available trace data into @p buf. The oldest available byte is at offset 0.
+	 *
+	 * @note Set to @c NULL if this operation is not supported by the trace backend.
+	 *
+	 * @param offset Start offset from the oldest available byte.
+	 * @param buf Output buffer.
+	 * @param len Size of output buffer.
+	 *
+	 * @return Number of bytes copied on success, negative errno on failure.
+	 */
+	int (*peek_at)(size_t offset, void *buf, size_t len);
+
 	/**
 	 * @brief Erase all captured trace data in the compile-time selected trace backend.
 	 *

lib/nrf_modem_lib/nrf_modem_lib_trace.c

@@ -516,6 +516,15 @@ int nrf_modem_lib_trace_read(uint8_t *buf, size_t len)
 	return read;
 }
 
+int nrf_modem_lib_trace_peek_at(size_t offset, uint8_t *buf, size_t len)
+{
+	if (!trace_backend.peek_at) {
+		return -ENOTSUP;
+	}
+
+	return trace_backend.peek_at(offset, buf, len);
+}
+
 int nrf_modem_lib_trace_clear(void)
 {
 	int err;