[RFC PATCH 1/7] lib: add helper to read strings from sysfs files

[Tomasz Duszynski <tduszynski@marvell.com>]

Reading strings from sysfs files is a re-occurring pattern
hence add helper for doing that.

Signed-off-by: Tomasz Duszynski <tduszynski@marvell.com>
---
 app/test/test_eal_fs.c          | 108 ++++++++++++++++++++++++++++----
 lib/eal/common/eal_filesystem.h |   6 ++
 lib/eal/unix/eal_filesystem.c   |  24 ++++---
 lib/eal/version.map             |   3 +
 4 files changed, 123 insertions(+), 18 deletions(-)

diff --git a/app/test/test_eal_fs.c b/app/test/test_eal_fs.c
index b3686edcb4..6c373fc7f1 100644
--- a/app/test/test_eal_fs.c
+++ b/app/test/test_eal_fs.c
@@ -20,12 +20,33 @@ test_eal_fs(void)
 
 #else
 
+static int
+temp_create(char *filename, size_t len)
+{
+	char file_template[] = "/tmp/eal_test_XXXXXX";
+	char proc_path[PATH_MAX];
+	int fd;
+
+	fd = mkstemp(file_template);
+	if (fd == -1) {
+		perror("mkstemp() failure");
+		return -1;
+	}
+
+	snprintf(proc_path, sizeof(proc_path), "/proc/self/fd/%d", fd);
+	if (readlink(proc_path, filename, len) < 0) {
+		perror("readlink() failure");
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
 static int
 test_parse_sysfs_value(void)
 {
 	char filename[PATH_MAX] = "";
-	char proc_path[PATH_MAX];
-	char file_template[] = "/tmp/eal_test_XXXXXX";
 	int tmp_file_handle = -1;
 	FILE *fd = NULL;
 	unsigned valid_number;
@@ -40,16 +61,10 @@ test_parse_sysfs_value(void)
 
 	/* get a temporary filename to use for all tests - create temp file handle and then
 	 * use /proc to get the actual file that we can open */
-	tmp_file_handle = mkstemp(file_template);
-	if (tmp_file_handle == -1) {
-		perror("mkstemp() failure");
+	tmp_file_handle = temp_create(filename, sizeof(filename));
+	if (tmp_file_handle < 0)
 		goto error;
-	}
-	snprintf(proc_path, sizeof(proc_path), "/proc/self/fd/%d", tmp_file_handle);
-	if (readlink(proc_path, filename, sizeof(filename)) < 0) {
-		perror("readlink() failure");
-		goto error;
-	}
+
 	printf("Temporary file is: %s\n", filename);
 
 	/* test we get an error value if we use file before it's created */
@@ -175,11 +190,82 @@ test_parse_sysfs_value(void)
 	return -1;
 }
 
+static int
+test_parse_sysfs_string(void)
+{
+	const char *teststr = "the quick brown dog jumps over the lazy fox\n";
+	char filename[PATH_MAX] = "";
+	char buf[BUFSIZ] = { };
+	int tmp_file_handle;
+	FILE *fd = NULL;
+
+#ifdef RTE_EXEC_ENV_FREEBSD
+	/* BSD doesn't have /proc/pid/fd */
+	return 0;
+#endif
+	printf("Testing function eal_parse_sysfs_string()\n");
+
+	/* get a temporary filename to use for all tests - create temp file handle and then
+	 * use /proc to get the actual file that we can open
+	 */
+	tmp_file_handle = temp_create(filename, sizeof(filename));
+	if (tmp_file_handle < 0)
+		goto error;
+
+	printf("Temporary file is: %s\n", filename);
+
+	/* test we get an error value if we use file before it's created */
+	printf("Test reading a missing file ...\n");
+	if (eal_parse_sysfs_string("/dev/not-quite-null", buf, sizeof(buf)) == 0) {
+		printf("Error with eal_parse_sysfs_string() - returned success on reading empty file\n");
+		goto error;
+	}
+	printf("Confirmed return error when reading empty file\n");
+
+	/* test reading a string from file */
+	printf("Test reading string ...\n");
+	fd = fopen(filename, "w");
+	if (fd == NULL) {
+		printf("line %d, Error opening %s: %s\n", __LINE__, filename, strerror(errno));
+		goto error;
+	}
+	fprintf(fd, "%s", teststr);
+	fclose(fd);
+	fd = NULL;
+	if (eal_parse_sysfs_string(filename, buf, sizeof(buf) - 1) < 0) {
+		printf("eal_parse_sysfs_string() returned error - test failed\n");
+		goto error;
+	}
+	if (strcmp(teststr, buf)) {
+		printf("Invalid string read by eal_parse_sysfs_string() - test failed\n");
+		goto error;
+	}
+	/* don't print newline */
+	buf[strlen(buf) - 1] = '\0';
+	printf("Read '%s\\n' ok\n", buf);
+
+	close(tmp_file_handle);
+	unlink(filename);
+	printf("eal_parse_sysfs_string() - OK\n");
+	return 0;
+
+error:
+	if (fd)
+		fclose(fd);
+	if (tmp_file_handle > 0)
+		close(tmp_file_handle);
+	if (filename[0] != '\0')
+		unlink(filename);
+	return -1;
+}
+
 static int
 test_eal_fs(void)
 {
 	if (test_parse_sysfs_value() < 0)
 		return -1;
+	if (test_parse_sysfs_string() < 0)
+		return -1;
 	return 0;
 }
 
diff --git a/lib/eal/common/eal_filesystem.h b/lib/eal/common/eal_filesystem.h
index 5d21f07c20..79bcc5ca1f 100644
--- a/lib/eal/common/eal_filesystem.h
+++ b/lib/eal/common/eal_filesystem.h
@@ -104,4 +104,10 @@ eal_get_hugefile_path(char *buffer, size_t buflen, const char *hugedir, int f_id
  * Used to read information from files on /sys */
 int eal_parse_sysfs_value(const char *filename, unsigned long *val);
 
+/** Function to read a string from a file on the filesystem.
+ * Used to read information for files in /sys
+ */
+__rte_experimental
+int eal_parse_sysfs_string(const char *filename, char *str, size_t size);
+
 #endif /* EAL_FILESYSTEM_H */
diff --git a/lib/eal/unix/eal_filesystem.c b/lib/eal/unix/eal_filesystem.c
index afbab9368a..8ed10094be 100644
--- a/lib/eal/unix/eal_filesystem.c
+++ b/lib/eal/unix/eal_filesystem.c
@@ -76,12 +76,9 @@ int eal_create_runtime_dir(void)
 	return 0;
 }
 
-/* parse a sysfs (or other) file containing one integer value */
-int eal_parse_sysfs_value(const char *filename, unsigned long *val)
+int eal_parse_sysfs_string(const char *filename, char *str, size_t size)
 {
 	FILE *f;
-	char buf[BUFSIZ];
-	char *end = NULL;
 
 	if ((f = fopen(filename, "r")) == NULL) {
 		RTE_LOG(ERR, EAL, "%s(): cannot open sysfs value %s\n",
@@ -89,19 +86,32 @@ int eal_parse_sysfs_value(const char *filename, unsigned long *val)
 		return -1;
 	}
 
-	if (fgets(buf, sizeof(buf), f) == NULL) {
+	if (fgets(str, size, f) == NULL) {
 		RTE_LOG(ERR, EAL, "%s(): cannot read sysfs value %s\n",
 			__func__, filename);
 		fclose(f);
 		return -1;
 	}
+	fclose(f);
+	return 0;
+}
+
+/* parse a sysfs (or other) file containing one integer value */
+int eal_parse_sysfs_value(const char *filename, unsigned long *val)
+{
+	char buf[BUFSIZ];
+	char *end = NULL;
+	int ret;
+
+	ret = eal_parse_sysfs_string(filename, buf, sizeof(buf));
+	if (ret < 0)
+		return ret;
+
 	*val = strtoul(buf, &end, 0);
 	if ((buf[0] == '\0') || (end == NULL) || (*end != '\n')) {
 		RTE_LOG(ERR, EAL, "%s(): cannot parse sysfs value %s\n",
 				__func__, filename);
-		fclose(f);
 		return -1;
 	}
-	fclose(f);
 	return 0;
 }
diff --git a/lib/eal/version.map b/lib/eal/version.map
index 7ad12a7dc9..2dbc10e6be 100644
--- a/lib/eal/version.map
+++ b/lib/eal/version.map
@@ -440,6 +440,9 @@ EXPERIMENTAL {
 	rte_thread_detach;
 	rte_thread_equal;
 	rte_thread_join;
+
+	# added in 23.03
+	eal_parse_sysfs_string; # WINDOWS_NO_EXPORT
 };
 
 INTERNAL {
-- 
2.25.1