linux-kernel - [RFC PATCH 7/8] firewire: core: detect model name for legacy layout of configuration ROM

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Message-Id: <20231217103012.41273-8-o-takashi@sakamocchi.jp>
Date: Sun, 17 Dec 2023 19:30:10 +0900
From: Takashi Sakamoto <o-takashi@...amocchi.jp>
To: linux1394-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Cc: adamg@...ox.com
Subject: [RFC PATCH 7/8] firewire: core: detect model name for legacy layout of configuration ROM

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_name'
attribute appears in node device, however it is probable to see the other
types of descriptor leaf if the vendor directory includes.

Signed-off-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
---
 drivers/firewire/core-device.c  | 23 ++++++++++++++++-------
 drivers/firewire/csr-api-test.c |  5 +++--
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
index dad5c9937b78..f7a11004f972 100644
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -315,17 +315,25 @@ static ssize_t show_text_leaf(struct device *dev,
 {
 	struct config_rom_attribute *attr =
 		container_of(dattr, struct config_rom_attribute, attr);
-	const u32 *dir;
+	const u32 *directories[] = {NULL, NULL};
 	size_t bufsize;
 	char dummy_buf[2];
-	int ret;
+	int i, ret;
 
 	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;
+
+		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);
+	}
 
 	if (buf) {
 		bufsize = PAGE_SIZE - 1;
@@ -334,7 +342,8 @@ static ssize_t show_text_leaf(struct device *dev,
 		bufsize = 1;
 	}
 
-	ret = fw_csr_string(dir, attr->key, buf, bufsize);
+	for (i = 0; i < ARRAY_SIZE(directories) && directories[i]; ++i)
+		ret = fw_csr_string(directories[i], attr->key, buf, bufsize);
 
 	if (ret >= 0) {
 		/* Strip trailing whitespace and add newline. */
diff --git a/drivers/firewire/csr-api-test.c b/drivers/firewire/csr-api-test.c
index 7278e7b927a8..779146d0cfba 100644
--- a/drivers/firewire/csr-api-test.c
+++ b/drivers/firewire/csr-api-test.c
@@ -206,8 +206,9 @@ static void csr_api_legacy_avc_device(struct kunit *test)
 	// Descriptor leaf entry for vendor is not found.
 	KUNIT_EXPECT_LT(test, show_text_leaf(node_dev, &config_rom_attributes[5].attr, buf), 0);
 
-	// Descriptor leaf entry for model is not found.
-	KUNIT_EXPECT_LT(test, show_text_leaf(node_dev, &config_rom_attributes[6].attr, buf), 0);
+	// Descriptor leaf entry for model is found.
+	KUNIT_EXPECT_GT(test, show_text_leaf(node_dev, &config_rom_attributes[6].attr, buf), 0);
+	KUNIT_EXPECT_STREQ(test, buf, "ABCDEFGHIJ\n");
 
 	// For entries in unit 0 directory.
 
-- 
2.39.2