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[PATCH 2/3] tools lib api fs: Add sysfs__write_int function

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  [PATCH 2/3] tools lib api fs: Add sysfs__write_int function kan.liang@intel.com - 2017-03-23 19:40 +0100
    RE: [PATCH 2/3] tools lib api fs: Add sysfs__write_int function "Elliott, Robert (Persistent Memory)" <elliott@hpe.com> - 2017-03-28 05:40 +0200

#1607789 — [PATCH 2/3] tools lib api fs: Add sysfs__write_int function

From: Kan Liang <Kan.liang@intel.com>

Adding sysfs__write_int function to ease up writing int to sysfs.
New interface is:

  int sysfs__write_int(const char *entry, int value);

Also, introducing filename__write_int which is useful for new helpers to
write sysctl values.

Signed-off-by: Kan Liang <Kan.liang@intel.com>
---
 tools/lib/api/fs/fs.c | 29 +++++++++++++++++++++++++++++
 tools/lib/api/fs/fs.h |  4 ++++
 2 files changed, 33 insertions(+)

diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 809c772..de4f74e 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -387,6 +387,22 @@ int filename__read_str(const char *filename, char **buf, size_t *sizep)
 	return err;
 }
 
+int filename__write_int(const char *filename, int value)
+{
+	int fd = open(filename, O_WRONLY), err = -1;
+	char buf[64];
+
+	if (fd < 0)
+		return err;
+
+	sprintf(buf, "%d", value);
+	if (write(fd, buf, sizeof(buf)) == sizeof(buf))
+		err = 0;
+
+	close(fd);
+	return err;
+}
+
 int procfs__read_str(const char *entry, char **buf, size_t *sizep)
 {
 	char path[PATH_MAX];
@@ -480,3 +496,16 @@ int sysctl__read_int(const char *sysctl, int *value)
 
 	return filename__read_int(path, value);
 }
+
+int sysfs__write_int(const char *entry, int value)
+{
+	char path[PATH_MAX];
+	const char *sysfs = sysfs__mountpoint();
+
+	if (!sysfs)
+		return -1;
+
+	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
+
+	return filename__write_int(path, value);
+}
diff --git a/tools/lib/api/fs/fs.h b/tools/lib/api/fs/fs.h
index 956c211..4560534 100644
--- a/tools/lib/api/fs/fs.h
+++ b/tools/lib/api/fs/fs.h
@@ -31,6 +31,8 @@ int filename__read_int(const char *filename, int *value);
 int filename__read_ull(const char *filename, unsigned long long *value);
 int filename__read_str(const char *filename, char **buf, size_t *sizep);
 
+int filename__write_int(const char *filename, int value);
+
 int procfs__read_str(const char *entry, char **buf, size_t *sizep);
 
 int sysctl__read_int(const char *sysctl, int *value);
@@ -38,4 +40,6 @@ int sysfs__read_int(const char *entry, int *value);
 int sysfs__read_ull(const char *entry, unsigned long long *value);
 int sysfs__read_str(const char *entry, char **buf, size_t *sizep);
 int sysfs__read_bool(const char *entry, bool *value);
+
+int sysfs__write_int(const char *entry, int value);
 #endif /* __API_FS__ */
-- 
2.7.4

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#1610275

> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-
> owner@vger.kernel.org] On Behalf Of kan.liang@intel.com
> Sent: Thursday, March 23, 2017 1:26 PM
> Subject: [PATCH 2/3] tools lib api fs: Add sysfs__write_int function
...
> diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
...
> +
> +int sysfs__write_int(const char *entry, int value)
> +{
> +	char path[PATH_MAX];
> +	const char *sysfs = sysfs__mountpoint();
> +
> +	if (!sysfs)
> +		return -1;
> +
> +	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
> +
> +	return filename__write_int(path, value);

In the unlikely event of an overflow, it would be safer to confirm that
the string fit into the path array (by using scnprintf()?) before trying
to open that path.

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