1 files changed, 241 insertions, 0 deletions
diff --git a/sysfs_attr.c b/sysfs_attr.c
new file mode 100644
index 0000000..6d67711
--- /dev/null
+++ b/sysfs_attr.c
@@ -0,0 +1,241 @@
+/*
+ * sysfs_dir.c
+ *
+ * Directory utility functions for libsysfs
+ *
+ * Copyright (C) IBM Corp. 2003-2005
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ */
+#include "libsysfs.h"
+#include "sysfs.h"
+
+/**
+ * sysfs_close_attribute: closes and cleans up attribute
+ * @sysattr: attribute to close.
+ */
+void sysfs_close_attribute(struct sysfs_attribute *sysattr)
+{
+	if (sysattr) {
+		if (sysattr->value)
+			free(sysattr->value);
+		free(sysattr);
+	}
+}
+
+/**
+ * alloc_attribute: allocates and initializes attribute structure
+ * returns struct sysfs_attribute with success and NULL with error.
+ */
+static struct sysfs_attribute *alloc_attribute(void)
+{
+	return (struct sysfs_attribute *)
+			calloc(1, sizeof(struct sysfs_attribute));
+}
+
+/**
+ * sysfs_open_attribute: creates sysfs_attribute structure
+ * @path: path to attribute.
+ * returns sysfs_attribute struct with success and NULL with error.
+ */
+struct sysfs_attribute *sysfs_open_attribute(const char *path)
+{
+	struct sysfs_attribute *sysattr = NULL;
+	struct stat fileinfo;
+
+	if (!path) {
+		errno = EINVAL;
+		return NULL;
+	}
+	sysattr = alloc_attribute();
+	if (!sysattr) {
+		dprintf("Error allocating attribute at %s\n", path);
+		return NULL;
+	}
+	if (sysfs_get_name_from_path(path, sysattr->name,
+				SYSFS_NAME_LEN) != 0) {
+		dprintf("Error retrieving attrib name from path: %s\n", path);
+		sysfs_close_attribute(sysattr);
+		return NULL;
+	}
+	safestrcpy(sysattr->path, path);
+	if ((stat(sysattr->path, &fileinfo)) != 0) {
+		dprintf("Stat failed: No such attribute?\n");
+		sysattr->method = 0;
+		free(sysattr);
+		sysattr = NULL;
+	} else {
+		if (fileinfo.st_mode & S_IRUSR)
+			sysattr->method |= SYSFS_METHOD_SHOW;
+		if (fileinfo.st_mode & S_IWUSR)
+			sysattr->method |= SYSFS_METHOD_STORE;
+	}
+
+	return sysattr;
+}
+
+/**
+ * sysfs_read_attribute: reads value from attribute
+ * @sysattr: attribute to read
+ * returns 0 with success and -1 with error.
+ */
+int sysfs_read_attribute(struct sysfs_attribute *sysattr)
+{
+	char *fbuf = NULL;
+	char *vbuf = NULL;
+	ssize_t length = 0;
+	long pgsize = 0;
+	int fd;
+
+	if (!sysattr) {
+		errno = EINVAL;
+		return -1;
+	}
+	if (!(sysattr->method & SYSFS_METHOD_SHOW)) {
+		dprintf("Show method not supported for attribute %s\n",
+			sysattr->path);
+		errno = EACCES;
+		return -1;
+	}
+	pgsize = getpagesize();
+	fbuf = (char *)calloc(1, pgsize+1);
+	if (!fbuf) {
+		dprintf("calloc failed\n");
+		return -1;
+	}
+	if ((fd = open(sysattr->path, O_RDONLY)) < 0) {
+		dprintf("Error reading attribute %s\n", sysattr->path);
+		free(fbuf);
+		return -1;
+	}
+	length = read(fd, fbuf, pgsize);
+	if (length < 0) {
+		dprintf("Error reading from attribute %s\n", sysattr->path);
+		close(fd);
+		free(fbuf);
+		return -1;
+	}
+	if (sysattr->len > 0) {
+		if ((sysattr->len == length) &&
+				(!(strncmp(sysattr->value, fbuf, length)))) {
+			close(fd);
+			free(fbuf);
+			return 0;
+		}
+		free(sysattr->value);
+	}
+	sysattr->len = length;
+	close(fd);
+	vbuf = (char *)realloc(fbuf, length+1);
+	if (!vbuf) {
+		dprintf("realloc failed\n");
+		free(fbuf);
+		return -1;
+	}
+	sysattr->value = vbuf;
+
+	return 0;
+}
+
+/**
+ * sysfs_write_attribute: write value to the attribute
+ * @sysattr: attribute to write
+ * @new_value: value to write
+ * @len: length of "new_value"
+ * returns 0 with success and -1 with error.
+ */
+int sysfs_write_attribute(struct sysfs_attribute *sysattr,
+		const char *new_value, size_t len)
+{
+	int fd;
+	int length;
+
+	if (!sysattr || !new_value || len == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (!(sysattr->method & SYSFS_METHOD_STORE)) {
+		dprintf ("Store method not supported for attribute %s\n",
+			sysattr->path);
+		errno = EACCES;
+		return -1;
+	}
+	if (sysattr->method & SYSFS_METHOD_SHOW) {
+		/*
+		 * read attribute again to see if we can get an updated value
+		 */
+		if ((sysfs_read_attribute(sysattr))) {
+			dprintf("Error reading attribute\n");
+			return -1;
+		}
+		if ((strncmp(sysattr->value, new_value, sysattr->len)) == 0 &&
+				(len == sysattr->len)) {
+			dprintf("Attr %s already has the requested value %s\n",
+					sysattr->name, new_value);
+			return 0;
+		}
+	}
+	/*
+	 * open O_WRONLY since some attributes have no "read" but only
+	 * "write" permission
+	 */
+	if ((fd = open(sysattr->path, O_WRONLY)) < 0) {
+		dprintf("Error reading attribute %s\n", sysattr->path);
+		return -1;
+	}
+
+	length = write(fd, new_value, len);
+	if (length < 0) {
+		dprintf("Error writing to the attribute %s - invalid value?\n",
+			sysattr->name);
+		close(fd);
+		return -1;
+	} else if ((unsigned int)length != len) {
+		dprintf("Could not write %zd bytes to attribute %s\n",
+					len, sysattr->name);
+		/*
+		 * since we could not write user supplied number of bytes,
+		 * restore the old value if one available
+		 */
+		if (sysattr->method & SYSFS_METHOD_SHOW) {
+			length = write(fd, sysattr->value, sysattr->len);
+			close(fd);
+			return -1;
+		}
+	}
+
+	/*
+	 * Validate length that has been copied. Alloc appropriate area
+	 * in sysfs_attribute. Verify first if the attribute supports reading
+	 * (show method). If it does not, do not bother
+	 */
+	if (sysattr->method & SYSFS_METHOD_SHOW) {
+		if (length != sysattr->len) {
+			sysattr->value = (char *)realloc
+				(sysattr->value, length);
+			sysattr->len = length;
+			safestrcpymax(sysattr->value, new_value, length);
+		} else {
+			/*"length" of the new value is same as old one */
+			safestrcpymax(sysattr->value, new_value, length);
+		}
+	}
+
+	close(fd);
+	return 0;
+}
+