master 41a45373c1b 4/4: ; Add some comments in Tramp

[Michael Albinus]

branch: master
commit 41a45373c1b7f19b06b3666a359331a40e494313
Author: Michael Albinus <michael.albinus@gmx.de>
Commit: Michael Albinus <michael.albinus@gmx.de>

    ; Add some comments in Tramp
---
 lisp/net/tramp-gvfs.el |  2 +-
 lisp/net/tramp-sh.el   | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/lisp/net/tramp-gvfs.el b/lisp/net/tramp-gvfs.el
index 71ef8215ab0..577760f806c 100644
--- a/lisp/net/tramp-gvfs.el
+++ b/lisp/net/tramp-gvfs.el
@@ -980,8 +980,8 @@ or `dbus-call-method-asynchronously'."
   (vec bus service path interface)
   "Return all properties of INTERFACE.
 The call will be traced by Tramp with trace level 6."
-     ;; Check, that interface exists at object path.  Retrieve properties.
   (declare (indent 1) (debug t))
+  ;; Check, that interface exists at object path.  Retrieve properties.
   `(when (member
          ,interface
          (tramp-dbus-function
diff --git a/lisp/net/tramp-sh.el b/lisp/net/tramp-sh.el
index c42d9fd0529..eaf1298278f 100644
--- a/lisp/net/tramp-sh.el
+++ b/lisp/net/tramp-sh.el
@@ -4166,6 +4166,18 @@ This function expects to be in the right *tramp* buffer."
 ;; On hydra.nixos.org, the $PATH environment variable is too long to
 ;; send it.  This is likely not due to PATH_MAX, but PIPE_BUF.  We
 ;; check it, and use a temporary file in case of.  See Bug#33781.
+
+;; The PIPE_BUF in POSIX [1] can be as low as 512 [2]. Here are the values
+;; on various platforms:
+;;   - 512 on macOS, FreeBSD, NetBSD, OpenBSD, MirBSD, native Windows.
+;;   - 4 KiB on Linux, OSF/1, Cygwin, Haiku.
+;;   - 5 KiB on Solaris.
+;;   - 8 KiB on HP-UX, Plan9.
+;;   - 10 KiB on IRIX.
+;;   - 32 KiB on AIX, Minix.
+;; [1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html
+;; [2] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/limits.h.html
+;; See Bug#65324.
 (defun tramp-set-remote-path (vec)
   "Set the remote environment PATH to existing directories.
 I.e., for each directory in `tramp-remote-path', it is tested