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-rw-r--r--Documentation/filesystems/sysfs.txt9
1 files changed, 7 insertions, 2 deletions
diff --git a/Documentation/filesystems/sysfs.txt b/Documentation/filesystems/sysfs.txt
index 4598ef7b622b..7f27b8f840d0 100644
--- a/Documentation/filesystems/sysfs.txt
+++ b/Documentation/filesystems/sysfs.txt
@@ -176,8 +176,10 @@ implementations:
Recall that an attribute should only be exporting one value, or an
array of similar values, so this shouldn't be that expensive.
- This allows userspace to do partial reads and seeks arbitrarily over
- the entire file at will.
+ This allows userspace to do partial reads and forward seeks
+ arbitrarily over the entire file at will. If userspace seeks back to
+ zero or does a pread(2) with an offset of '0' the show() method will
+ be called again, rearmed, to fill the buffer.
- On write(2), sysfs expects the entire buffer to be passed during the
first write. Sysfs then passes the entire buffer to the store()
@@ -192,6 +194,9 @@ implementations:
Other notes:
+- Writing causes the show() method to be rearmed regardless of current
+ file position.
+
- The buffer will always be PAGE_SIZE bytes in length. On i386, this
is 4096.