Merge patch series "fs: regression-safe load <iface> for null_dev_desc_ok fstypes"

Vincent Jardin <[email protected]> says:

3 commits providing documentation of impacts and testing the dispatch
for null_dev_desc_ok fstypes (semihosting, ubifs, sandbox) in the
generic `load <iface> ...` command.

The test does not cover ubifs, I could not make it work with
qemu. Since the code logic is there and testing with semihost
is done, it should cover the needed cases.

Link: https://lore.kernel.org/r/[email protected]

5 files changed, 166 insertions, 2 deletions

diff --git a/doc/usage/cmd/load.rst b/doc/usage/cmd/load.rst
index bfa45c6f36c..bf2fffbed21 100644
--- a/doc/usage/cmd/load.rst
+++ b/doc/usage/cmd/load.rst
@@ -63,6 +63,39 @@ Example
     16 bytes read in 1 ms (15.6 KiB/s)
     =>
 
+Null-block-device interfaces
+----------------------------
+
+A few ``<interface>`` values have no underlying block device. Their
+filesystem implementations directly call a back-end (JTAG
+debugger, UBI volume, host running U-Boot under sandbox, ...) and
+ignore the ``<dev[:part]>`` field, which may be given as ``-``. So
+``load <iface> - <addr> <filename>`` works.
+
+semihosting
+    Read files from the host filesystem of an attached JTAG debugger
+    using the ARM semihosting protocol. Useful with OpenOCD.
+    Built when ``CONFIG_SEMIHOSTING=y``.
+
+ubifs
+    Read files from a UBIFS volume that has already been attached
+    and mounted with the ``ubi part`` + ``ubifsmount`` commands.
+    Built when ``CONFIG_CMD_UBIFS=y``.
+
+sandbox
+    Read files from the host filesystem the sandbox binary is
+    running under. Available on sandbox builds.
+
+The ``<dev[:part]>`` argument is conventionally written as ``-`` for
+these interfaces, to make it visible at the call site that the field
+is unused. The filesystem layer never looks at it.
+
+Example::
+
+    => load semihosting - ${kernel_addr_r} kernel.itb
+    9437184 bytes read in 412 ms (21.8 MiB/s)
+    =>
+
 Configuration
 -------------
 
diff --git a/fs/fs.c b/fs/fs.c
index 1ebda6f4ee2..2824c7defa2 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -461,11 +461,53 @@ const char *fs_get_type_name(void)
 	return fs_get_info(fs_type)->name;
 }
 
+/*
+ * Some fstypes (semihosting, ubifs) have no underlying block device
+ * and ignore the block_desc argument of their probe hook. The legacy
+ * commands (ubifsload, semihosting via env macros) just pass NULL;
+ * for "load <iface> ..." to behave the same, the dispatcher opts
+ * those fstypes in by name here, before any block-device lookup is
+ * attempted.
+ *
+ * Returns the matching fstype_info if @ifname names a fstype that
+ * opts into null_dev_desc_ok dispatch and the caller's @fstype filter
+ * permits it. Returns NULL otherwise.
+ */
+static struct fstype_info *fs_lookup_null_dev_info(const char *ifname,
+						   int fstype)
+{
+	struct fstype_info *info;
+	int i;
+
+	for (i = 0, info = fstypes; i < ARRAY_SIZE(fstypes); i++, info++) {
+		if (fstype != FS_TYPE_ANY && info->fstype != FS_TYPE_ANY &&
+		    fstype != info->fstype)
+			continue;
+		if (!info->null_dev_desc_ok || !info->name)
+			continue;
+		if (!strcmp(info->name, ifname))
+			return info;
+	}
+
+	return NULL;
+}
+
 int fs_set_blk_dev(const char *ifname, const char *dev_part_str, int fstype)
 {
 	struct fstype_info *info;
 	int part, i;
 
+	info = fs_lookup_null_dev_info(ifname, fstype);
+	if (info) {
+		fs_dev_desc = NULL;
+		memset(&fs_partition, 0, sizeof(fs_partition));
+		if (!info->probe(NULL, &fs_partition)) {
+			fs_type = info->fstype;
+			fs_dev_part = 0;
+			return 0;
+		}
+	}
+
 	part = part_get_info_by_dev_and_name_or_num(ifname, dev_part_str, &fs_dev_desc,
 						    &fs_partition, 1);
 	if (part < 0)
diff --git a/test/py/tests/test_load_sandbox.py b/test/py/tests/test_load_sandbox.py
new file mode 100644
index 00000000000..8d28a630e76
--- /dev/null
+++ b/test/py/tests/test_load_sandbox.py
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier:      GPL-2.0+
+# Copyright 2026 Free Mobile - Vincent Jardin
+
+"""Regression test for `load sandbox - <addr> <file>`.
+
+Exercises the null_dev_desc_ok dispatch added in
+"fs: dispatch null_dev_desc_ok filesystems before block lookup".
+
+It is the counterpart of test_load_semihosting.py
+"""
+
+import os
+import pytest
+
+
[email protected](scope='session')
+def sandbox_fixture(u_boot_config):
+    """Host-staged fixture file read by `load sandbox`."""
+    path = os.path.join(u_boot_config.persistent_data_dir,
+                        'sandbox-fstype.txt')
+    with open(path, 'w', encoding='utf-8') as f:
+        f.write('Das U-Boot\n')   # 11 bytes, same as test_hostfs.py / semihosting
+    yield path
+    os.remove(path)
+
+
[email protected]('sandbox')
+def test_sandbox_load(ubman, sandbox_fixture):
+    """Run `load sandbox - <addr> <file>` and check the bytes."""
+    response = ubman.run_command(
+        f'load sandbox - $loadaddr {sandbox_fixture}')
+
+    # Fixture is "Das U-Boot\n" (11 bytes).
+    assert '11 bytes read' in response
+
+    # crc32("Das U-Boot\n") -- identical to the semihosting / hostfs checks.
+    response = ubman.run_command('crc32 $loadaddr $filesize')
+    assert '==> 60cfccfc' in response
+
+
[email protected]('sandbox')
+def test_sandbox_load_offset(ubman, sandbox_fixture):
+    """Run the [bytes] [pos] variant through the same dispatch."""
+    response = ubman.run_command(
+        f'load sandbox - $loadaddr {sandbox_fixture} 4 6')
+    # bytes=4 pos=6 over "Das U-Boot\n" -> "Boot".
+    assert '4 bytes read' in response
+
+    # crc32("Boot")
+    response = ubman.run_command('crc32 $loadaddr $filesize')
+    assert '==> e6df01fa' in response
diff --git a/test/py/tests/test_semihosting/conftest.py b/test/py/tests/test_semihosting/conftest.py
index b00d8f4ea9c..6b7f3f3c2d9 100644
--- a/test/py/tests/test_semihosting/conftest.py
+++ b/test/py/tests/test_semihosting/conftest.py
@@ -6,9 +6,9 @@
 import os
 import pytest
 
[email protected](scope='session')
[email protected](scope='function')
 def semihosting_data(u_boot_config):
-    """Set up a file system to be used in semihosting tests
+    """Set up a new file for each semihosting test
 
     Args:
         u_boot_config -- U-Boot configuration.
diff --git a/test/py/tests/test_semihosting/test_load_semihosting.py b/test/py/tests/test_semihosting/test_load_semihosting.py
new file mode 100644
index 00000000000..7c2eb72c69a
--- /dev/null
+++ b/test/py/tests/test_semihosting/test_load_semihosting.py
@@ -0,0 +1,38 @@
+# SPDX-License-Identifier:      GPL-2.0+
+# Copyright 2026 Free Mobile - Vincent Jardin
+
+"""Regression test for `load semihosting - <addr> <file>`.
+
+Companion to test_hostfs.py: same fixture, same crc32, different
+fstype routing:
+see the doc/usage/cmd/load.rst "Null-block-device interfaces" section.
+"""
+
+import pytest
+
+
[email protected]('semihosting')
+def test_semihosting_load(ubman, semihosting_data):
+    """Run `load semihosting - <addr> <file>` and check the bytes."""
+    response = ubman.run_command(
+        f'load semihosting - $loadaddr {semihosting_data}')
+
+    # Fixture is "Das U-Boot\n" (11 bytes).
+    assert '11 bytes read' in response
+
+    # crc32("Das U-Boot\n")
+    response = ubman.run_command('crc32 $loadaddr $filesize')
+    assert '==> 60cfccfc' in response
+
+
[email protected]('semihosting')
+def test_semihosting_load_offset(ubman, semihosting_data):
+    """Run the [bytes] [pos] variant through the same dispatch."""
+    response = ubman.run_command(
+        f'load semihosting - $loadaddr {semihosting_data} 4 6')
+    # bytes=4 pos=6 over "Das U-Boot\n" -> "Boot".
+    assert '4 bytes read' in response
+
+    # crc32("Boot")
+    response = ubman.run_command('crc32 $loadaddr $filesize')
+    assert '==> e6df01fa' in response