app: nrfcloud: Add GCI support to cellpos

[trantanen]

Implement cell positioning similarly to Location library meaning AT%NCELLMEAS will be done 1-3 times depending on how many cells are requested and found in each attempt. Implementation done by copying GCI parsing from lte_lc and use of 1-3 AT%NCELLMEAS operations from location library.

Use of memory seen from numbers before:

           FLASH:      363716 B     413546 B     87.95%
             RAM:      175600 B       206 KB     83.24%

After:

           FLASH:      367148 B     413546 B     88.78%
             RAM:      175616 B       206 KB     83.25%

This change removes use of modem_info from sm_at_nrfcloud.c. It is still needed for nrf_provisioning and nrf_cloud_agnss.

Jira: SM-223

TODO:

• Squash commits. They exist to show reviewers a bit on what has been done.
• Verify A-GNSS functionality
• Unit tests

[github-actions]

You can find the documentation preview for this PR here.

[trantanen]

This is ready for review. I'll try to add unit tests also into the PR.
A lot of the parsing functions have been copied from lte_lc and I'm not sure how much we should fine-tune them.
The logical change of using AT%NCELLMEAS from SM instead of host triggering it is something to be noted.
I'd like to get this merged in a week or so to get testing for this over the following weeks in CI.

[Copilot]

Pull request overview

This PR adds internal AT%NCELLMEAS-based cellular positioning for AT#XNRFCLOUDPOS, including GCI parsing, and updates nRF Cloud/GNSS integration plus related documentation.

Changes:

• Reworks nRF Cloud location requests from <cell_pos> modes to a <cell_count>-based measurement flow.
• Adds NCELLMEAS/GCI parsing and asynchronous location request handling.
• Updates A-GNSS cell-info collection and command documentation/migration notes.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 15 comments.

Show a summary per file

File	Description
doc/releases/migration_notes_v2.0.0.rst	Documents the AT#XNRFCLOUDPOS parameter migration.
doc/releases/migration_notes_ncs_slm_v3.1.x.rst	Adds migration guidance for the new nRF Cloud positioning behavior.
doc/app/at_nrfcloud.rst	Updates command reference syntax and notes for <cell_count> and internal NCELLMEAS use.
app/src/sm_at_nrfcloud.h	Replaces single-cell info API with the new NCELLMEAS helper declaration.
app/src/sm_at_nrfcloud.c	Implements NCELLMEAS/GCI parsing and location request orchestration.
app/src/sm_at_gnss.c	Switches A-GNSS network info collection to the new NCELLMEAS helper.

Comments suppressed due to low confidence (2)

app/src/sm_at_nrfcloud.c:919

• This PLMN string is also read with at_parser_string_get() but is not NUL-terminated before string_to_int(&tmp_str[3], ...) is called. Because the parser uses memcpy, the MNC parse can read beyond the PLMN field and produce spurious failures or incorrect MCC/MNC values for GCI cells.

		curr_index++;
		err = at_parser_string_get(&parser, curr_index, tmp_str, &len);
		if (err) {
			LOG_ERR("Could not parse plmn, error: %d", err);
			goto clean_exit;
		}

		/* Read MNC and store as integer. The MNC starts as the fourth character
		 * in the string, following three characters long MCC.
		 */
		err = string_to_int(&tmp_str[3], 10, &parsed_cell.mnc);
		if (err) {

app/src/sm_at_nrfcloud.c:1055

• For the normal %NCELLMEAS format, the first neighbor field is at index AT_NCELLMEAS_PRE_NCELLS_PARAMS_COUNT (the previous parser used offset 11). Initializing curr_index to 11 and then pre-incrementing in parse_ncellmeas_neighbors() starts at index 12, so neighbor fields are shifted and parsed into the wrong struct members.

	int err, status, tmp;
	struct at_parser parser;
	size_t count = 0;
	int curr_index = AT_NCELLMEAS_PRE_NCELLS_PARAMS_COUNT;

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[MarkusLassila]

This is getting difficult to review.

Approving as this needs CI-time and testing.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 7 comments.

[MarkusLassila]

The code changes are OK.

Rebase, fix the problems in compliance and the flash running out.

[divipillai]

Shouldn't these changes only be in the 2.0 migration guide?

[trantanen]

No. Those who transition from NCS SLM 3.1.1 to SM v2.0.0 needs to do same changes.