From 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 21 Sep 2026 18:24:42 +0800 Subject: KVM: Don't pre-reserve xarray entries when storing empty/NULL attributes Skip the xarray reservation loop when clearing all memory attributes, as storing NULL only erases the entry and never needs to allocate, so no reservation (and no cleanup of a failed one) is required in that case. Suggested-by: Sean Christopherson Cc: David Ballesteros Signed-off-by: Zeng Chi Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com [sean: split to separate patch] Signed-off-by: Sean Christopherson --- Documentation/admin-guide/braille-console.rst | 38 +++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100644 Documentation/admin-guide/braille-console.rst (limited to 'Documentation/admin-guide/braille-console.rst') diff --git a/Documentation/admin-guide/braille-console.rst b/Documentation/admin-guide/braille-console.rst new file mode 100644 index 000000000..153472e93 --- /dev/null +++ b/Documentation/admin-guide/braille-console.rst @@ -0,0 +1,38 @@ +Linux Braille Console +===================== + +To get early boot messages on a braille device (before userspace screen +readers can start), you first need to compile the support for the usual serial +console (see :ref:`Documentation/admin-guide/serial-console.rst `), and +for braille device +(in :menuselection:`Device Drivers --> Accessibility support --> Console on braille device`). + +Then you need to specify a ``console=brl``, option on the kernel command line, the +format is:: + + console=brl,serial_options... + +where ``serial_options...`` are the same as described in +:ref:`Documentation/admin-guide/serial-console.rst `. + +So for instance you can use ``console=brl,ttyS0`` if the braille device is connected to the first serial port, and ``console=brl,ttyS0,115200`` to +override the baud rate to 115200, etc. + +By default, the braille device will just show the last kernel message (console +mode). To review previous messages, press the Insert key to switch to the VT +review mode. In review mode, the arrow keys permit to browse in the VT content, +`PAGE-UP`/`PAGE-DOWN` keys go at the top/bottom of the screen, and +the `HOME` key goes back +to the cursor, hence providing very basic screen reviewing facility. + +Sound feedback can be obtained by adding the ``braille_console.sound=1`` kernel +parameter. + +For simplicity, only one braille console can be enabled, other uses of +``console=brl,...`` will be discarded. Also note that it does not interfere with +the console selection mechanism described in +:ref:`Documentation/admin-guide/serial-console.rst `. + +For now, only the VisioBraille device is supported. + +Samuel Thibault -- cgit v1.3.1