[RFC PATCH 6/8] firewire: core: detect numeric model identifier for legacy layout of configuration ROM

[Takashi S. <o-t...@sa...>]

As the part of support for legacy layout of configuration ROM, this
commit traverse vendor directory as well as root directory when showing
device attribute for node device. This change expects 'model' attribute
appears in node device, however it is probable to see the other types of
immediate values if the vendor directory includes.

Signed-off-by: Takashi Sakamoto <o-t...@sa...>
---
 drivers/firewire/core-device.c  | 57 +++++++++++++++++++++++++--------
 drivers/firewire/csr-api-test.c |  5 +--
 2 files changed, 47 insertions(+), 15 deletions(-)

diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
index 14c7461c05f6..dad5c9937b78 100644
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -49,6 +49,22 @@ int fw_csr_iterator_next(struct fw_csr_iterator *ci, int *key, int *value)
 }
 EXPORT_SYMBOL(fw_csr_iterator_next);
 
+static const u32 *search_directory(const u32 *directory, int search_key)
+{
+	struct fw_csr_iterator ci;
+	int key, value;
+
+	search_key |= CSR_DIRECTORY;
+
+	fw_csr_iterator_init(&ci, directory);
+	while (fw_csr_iterator_next(&ci, &key, &value)) {
+		if (key == search_key)
+			return ci.p - 1 + value;
+	}
+
+	return NULL;
+}
+
 static const u32 *search_leaf(const u32 *directory, int search_key)
 {
 	struct fw_csr_iterator ci;
@@ -253,27 +269,42 @@ static ssize_t show_immediate(struct device *dev,
 	struct config_rom_attribute *attr =
 		container_of(dattr, struct config_rom_attribute, attr);
 	struct fw_csr_iterator ci;
-	const u32 *dir;
-	int key, value, ret = -ENOENT;
+	const u32 *directories[] = {NULL, NULL};
+	int i, value = -1;
 
 	down_read(&fw_device_rwsem);
 
-	if (is_fw_unit(dev))
-		dir = fw_unit(dev)->directory;
-	else
-		dir = fw_device(dev)->config_rom + ROOT_DIR_OFFSET;
+	if (is_fw_unit(dev)) {
+		directories[0] = fw_unit(dev)->directory;
+	} else {
+		const u32 *root_directory = fw_device(dev)->config_rom + ROOT_DIR_OFFSET;
 
-	fw_csr_iterator_init(&ci, dir);
-	while (fw_csr_iterator_next(&ci, &key, &value))
-		if (attr->key == key) {
-			ret = snprintf(buf, buf ? PAGE_SIZE : 0,
-				       "0x%06x\n", value);
-			break;
+		directories[0] = root_directory;
+
+		// Legacy layout of configuration ROM described in Annex 1 of 'Configuration ROM
+		// for AV/C Devices 1.0 (December 12, 2000, 1394 Trading Association, TA Document
+		// 1999027)'.
+		directories[1] = search_directory(root_directory, CSR_VENDOR);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(directories) && !!directories[i]; ++i) {
+		int key, val;
+
+		fw_csr_iterator_init(&ci, directories[i]);
+		while (fw_csr_iterator_next(&ci, &key, &val)) {
+			if (attr->key == key) {
+				value = val;
+				break;
+			}
 		}
+	}
 
 	up_read(&fw_device_rwsem);
 
-	return ret;
+	if (value < 0)
+		return -ENOENT;
+
+	return snprintf(buf, buf ? PAGE_SIZE : 0, "0x%06x\n", value);
 }
 
 #define IMMEDIATE_ATTR(name, key)				\
diff --git a/drivers/firewire/csr-api-test.c b/drivers/firewire/csr-api-test.c
index 2430891c5dcb..7278e7b927a8 100644
--- a/drivers/firewire/csr-api-test.c
+++ b/drivers/firewire/csr-api-test.c
@@ -199,8 +199,9 @@ static void csr_api_legacy_avc_device(struct kunit *test)
 	KUNIT_EXPECT_GT(test, show_immediate(node_dev, &config_rom_attributes[0].attr, buf), 0);
 	KUNIT_EXPECT_STREQ(test, buf, "0x012345\n");
 
-	// Model immediate entry is not found.
-	KUNIT_EXPECT_LT(test, show_immediate(node_dev, &config_rom_attributes[4].attr, buf), 0);
+	// Model immediate entry is found.
+	KUNIT_EXPECT_GT(test, show_immediate(node_dev, &config_rom_attributes[4].attr, buf), 0);
+	KUNIT_EXPECT_STREQ(test, buf, "0xfedcba\n");
 
 	// Descriptor leaf entry for vendor is not found.
 	KUNIT_EXPECT_LT(test, show_text_leaf(node_dev, &config_rom_attributes[5].attr, buf), 0);
-- 
2.39.2