summaryrefslogtreecommitdiffstats
path: root/Documentation/filesystems/devpts.rst
diff options
context:
space:
mode:
authorAndi Shyti <andi.shyti@linux.intel.com>2026-08-22 14:19:12 +0200
committerAndi Shyti <andi.shyti@linux.intel.com>2026-08-22 14:19:34 +0200
commitd576a9561a1c80ae593539fb0ce0743d66825ac2 (patch)
tree68f6de7e06b350afa42edeea2f7f33f086014597 /Documentation/filesystems/devpts.rst
downloadlinux-stable-d576a9561a1c80ae593539fb0ce0743d66825ac2.tar.gz
linux-stable-d576a9561a1c80ae593539fb0ce0743d66825ac2.zip
Merge tag 'rust-i2c-for-7.3' into i2c/i2cgrafted
i2c: rust: mark I2cAdapter methods as inline A single cleanup for the Rust I2C abstractions, targeting 7.3. `I2cAdapter::get`, `inc_ref`, and `dec_ref` are trivial wrappers around `i2c_get_adapter`/`i2c_put_adapter` and were showing up as their own symbols in the build. Mark them `#[inline]` so they get folded into their callers instead. Signed-off-by: Igor Korotin <igor.korotin@linux.dev> * tag 'rust-i2c-for-7.3': i2c: rust: mark I2cAdapter methods as inline
Diffstat (limited to 'Documentation/filesystems/devpts.rst')
-rw-r--r--Documentation/filesystems/devpts.rst36
1 files changed, 36 insertions, 0 deletions
diff --git a/Documentation/filesystems/devpts.rst b/Documentation/filesystems/devpts.rst
new file mode 100644
index 000000000..b6324ab19
--- /dev/null
+++ b/Documentation/filesystems/devpts.rst
@@ -0,0 +1,36 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================
+The Devpts Filesystem
+=====================
+
+Each mount of the devpts filesystem is now distinct such that ptys
+and their indices allocated in one mount are independent from ptys
+and their indices in all other mounts.
+
+All mounts of the devpts filesystem now create a ``/dev/pts/ptmx`` node
+with permissions ``0000``.
+
+To retain backwards compatibility the a ptmx device node (aka any node
+created with ``mknod name c 5 2``) when opened will look for an instance
+of devpts under the name ``pts`` in the same directory as the ptmx device
+node.
+
+As an option instead of placing a ``/dev/ptmx`` device node at ``/dev/ptmx``
+it is possible to place a symlink to ``/dev/pts/ptmx`` at ``/dev/ptmx`` or
+to bind mount ``/dev/ptx/ptmx`` to ``/dev/ptmx``. If you opt for using
+the devpts filesystem in this manner devpts should be mounted with
+the ``ptmxmode=0666``, or ``chmod 0666 /dev/pts/ptmx`` should be called.
+
+Total count of pty pairs in all instances is limited by sysctls::
+
+ kernel.pty.max = 4096 - global limit
+ kernel.pty.reserve = 1024 - reserved for filesystems mounted from the initial mount namespace
+ kernel.pty.nr - current count of ptys
+
+Per-instance limit could be set by adding mount option ``max=<count>``.
+
+This feature was added in kernel 3.4 together with
+``sysctl kernel.pty.reserve``.
+
+In kernels older than 3.4 sysctl ``kernel.pty.max`` works as per-instance limit.