From nobody Fri Oct 3 13:30:16 2025 Received: from mail-qv1-f54.google.com (mail-qv1-f54.google.com [209.85.219.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 54D3B22157E for ; Mon, 1 Sep 2025 02:00:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.54 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756692044; cv=none; b=snw0Hl7Uv8VKzWcS36VcWBUrQIiKVh9KhYhsldAf87gnIdfH/LqPaBnlsPHUSZPPxhv0t7GT9rPgLi96ZeIW/sO2jr+FrX75daU9zxnx/sgII07VojLFxpdZ+dBCe4+ahhLWrr3Y9zZnvXcD95vlVI5t2cMHDuuKzr62tXfsejg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756692044; c=relaxed/simple; bh=VjSEQuTk8Aic2ULjMShGdIHNMpD4YMEhT97QSvsWINM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=WAXu853WN7BmScIZ5wsukoKOqUPzL8wWRcmqTbNlx0r2DAWe9QDR/OT6P48POD4ZYiMXeiayIkgzw4lPiduQo7IqCzbp7lqOpROLdu+y0pmkPnexmMSQOcDcUVh8vJbMq5eHVwo0Zi1AJUwCHw01qWA6QoizM/PSTcJEw8RZvBk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=MuMZeGxP; arc=none smtp.client-ip=209.85.219.54 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="MuMZeGxP" Received: by mail-qv1-f54.google.com with SMTP id 6a1803df08f44-70de9ffcfffso37798436d6.2 for ; Sun, 31 Aug 2025 19:00:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1756692041; x=1757296841; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=n71lxSZhtaKmDioqwBpuFWbtYkrE4A8cOtuolZZ4xFs=; b=MuMZeGxPjobAqstBIsavnDZ3cXis40ihN86kNASMweGoywuMnXw1GS35UC2EcFD7qO /ApEw92uXKd8FdAvpCOTEyLMe5PFAzkDj0J3OwHSTF2UbDh8X/Pq8JCbb1WLxNfwvSl+ cp1yLR82sfsHS59Ad7sOxBK7Gb8mfFAhxca3RyXE1dlU5Mn7V90+q7gybIkVHSJWoxiL mqAA2L3RhZbqmJh1Z+xUt5/0IdKJOTX7KF7ylLUOtdQORIMbYuNcFHt4z+D8nSCA6dVv GN3Q4I7d+rMNAaBxYM4DoOKGjDDvijEPCC/wcRbFauCivGluFfepkiOQQIkT4lXJ3MoR bfMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756692041; x=1757296841; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=n71lxSZhtaKmDioqwBpuFWbtYkrE4A8cOtuolZZ4xFs=; b=AbhNQrLQWjOy5dY0CvW0eYKpRoJggSZtZvnFcfEZK9INkIjWQFRlE731Qkim4Y6Vtm 1AusW9q0LklDKBFyTRogFTqDHNOxUtEedsIH+fLbnWBAX04XekzRlELyeNjjOZvCNNde +w01EAcifG2YthDBSJHwfMG5xPLT7YsA9fDmfsVeJKFVs8dS6DUnl4n4qYuXjbILBYX7 69dSLgd1kLSgTb2DH0kz7IXd1NwvUcxq7sr5zCpp311sgJvo1Vy17HWaZyI3fAFzfd07 lYlnWPyq84NO8TIx36nwafcjCKLUBbvwx7LSJ76h0oHHoYqdk/oqjgYeqduypB6XoYBb xLIg== X-Gm-Message-State: AOJu0YxgFu7aK2vyRQyiuOzFJw1wk8Z6Zy0AZLMD4o4RHNSD+aqh5e/3 oEtIeXPj6Lnbip3eLtecxVjlWGwR2PWKT/THyHFWiKwJ7l7C3e0rjPTqoTk/Jw== X-Gm-Gg: ASbGncvFesQ9sU3WHroNldwyGanoO5jEOh/EJuzFCD2hD2hga+y425XDWgqutyK05Ex LK4FhUnuCuWYWPj4A1/3OYqSiBoj2oUZaxvoeq2/nVHiKJnyPu/voVXYtsF3i7TgDAIkffoR5gw UVe1G9sFU6/+MAVIBVQo2S+NOuMWPvvnK5AL6H6R0afsnKg4cvGzOHyuH22Q3tCvQy+jbaeRceJ LPAlFmXLhSypUIYnpaUnl/YBynlQucX+6ytjTsXiQwcPjnCfFA08e6uLUyKihtDtxEXS6esmLVs u6J1i3BZXtQRd8xarwY6QYBZUzjSz08IUhd5a/2YZJsTSN1G5U27SFyuN7q4Tz4f6RKLFfIRsf8 5ix00S4nveABS61H0d4SjZUknzdnElDs9q+47JfsB31me30c8R1mRtiyIeZQTKQaDavaL X-Google-Smtp-Source: AGHT+IEaGu+VYdICMtJaTj4cIkBGcsfziLHVIU6jPygVTgEEWqJYHyBwxY2MAfxI6b1oIhohl443gg== X-Received: by 2002:a05:6214:2529:b0:70d:ce68:e019 with SMTP id 6a1803df08f44-70fac6f9d75mr58888606d6.8.1756692041077; Sun, 31 Aug 2025 19:00:41 -0700 (PDT) Received: from localhost (modemcable197.17-162-184.mc.videotron.ca. [184.162.17.197]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-70fb25c6f49sm32124496d6.15.2025.08.31.19.00.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 31 Aug 2025 19:00:40 -0700 (PDT) From: =?UTF-8?q?Jean-Fran=C3=A7ois=20Lessard?= To: Andy Shevchenko , Geert Uytterhoeven Cc: linux-kernel@vger.kernel.org Subject: [PATCH 5/5] docs: ABI: auxdisplay: document linedisp library sysfs attributes Date: Sun, 31 Aug 2025 22:00:29 -0400 Message-ID: <20250901020033.60196-6-jefflessard3@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250901020033.60196-1-jefflessard3@gmail.com> References: <20250901020033.60196-1-jefflessard3@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Add ABI documentation for sysfs attributes provided by the line-display auxdisplay library module. These attributes enable text message display and configuration on character-based auxdisplay devices. Documents previously undocumented attributes: - message, scroll_step_ms (introduced in v5.16) - map_seg7, map_seg14 (introduced in v6.9) Documents newly added attribute: - num_chars (targeted for v6.18) The line-display library is used by multiple auxdisplay drivers and can expose these attributes either on linedisp.N child devices or directly on parent auxdisplay devices. Signed-off-by: Jean-Fran=C3=A7ois Lessard --- .../ABI/testing/sysfs-auxdisplay-linedisp | 90 +++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-auxdisplay-linedisp diff --git a/Documentation/ABI/testing/sysfs-auxdisplay-linedisp b/Document= ation/ABI/testing/sysfs-auxdisplay-linedisp new file mode 100644 index 000000000..63c47f192 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-auxdisplay-linedisp @@ -0,0 +1,90 @@ +What: /sys/.../message +Date: October 2021 +KernelVersion: 5.16 +Description: + Controls the text message displayed on character line displays. + + Reading returns the current message with a trailing newline. + Writing updates the displayed message. Messages longer than the + display width will automatically scroll. Trailing newlines in + input are automatically trimmed. + + Writing an empty string clears the display. + + Example: + echo "Hello World" > message + cat message # Returns "Hello World\n" + +What: /sys/.../scroll_step_ms +Date: October 2021 +KernelVersion: 5.16 +Description: + Controls the scrolling speed for messages longer than the display + width, specified in milliseconds per scroll step. + + Setting to 0 disables scrolling. Default is 500ms. + + Example: + echo "250" > scroll_step_ms # 4Hz scrolling + cat scroll_step_ms # Returns "250\n" + +What: /sys/.../num_chars +Date: November 2025 +KernelVersion: 6.18 +Contact: Jean-Fran=C3=A7ois Lessard +Description: + Read-only attribute showing the character width capacity of + the line display device. Messages longer than this will scroll. + + Example: + cat num_chars # Returns "16\n" for 16-char display + +What: /sys/.../map_seg7 +Date: January 2024 +KernelVersion: 6.9 +Description: + Read/write binary blob representing the ASCII-to-7-segment + display conversion table used by the linedisp driver, as defined + by struct seg7_conversion_map in . + + Only visible on displays with 7-segment capability. + + This attribute is not human-readable. Writes must match the + struct size exactly, else -EINVAL is returned; reads return the + entire mapping as a binary blob. + + This interface and its implementation match existing conventions + used in segment-mapped display drivers since 2005. + + ABI note: This style of binary sysfs attribute *is an exception* + to current "one value per file, text only" sysfs rules, for + historical compatibility and driver uniformity. New drivers are + discouraged from introducing additional binary sysfs ABIs. + + Reference interface guidance: + - include/uapi/linux/map_to_7segment.h + +What: /sys/.../map_seg14 +Date: January 2024 +KernelVersion: 6.9 +Description: + Read/write binary blob representing the ASCII-to-14-segment + display conversion table used by the linedisp driver, as defined + by struct seg14_conversion_map in . + + Only visible on displays with 14-segment capability. + + This attribute is not human-readable. Writes must match the + struct size exactly, else -EINVAL is returned; reads return the + entire mapping as a binary blob. + + This interface and its implementation match existing conventions + used by segment-mapped display drivers since 2005. + + ABI note: This style of binary sysfs attribute *is an exception* + to current "one value per file, text only" sysfs rules, for + historical compatibility and driver uniformity. New drivers are + discouraged from introducing additional binary sysfs ABIs. + + Reference interface guidance: + - include/uapi/linux/map_to_14segment.h --=20 2.43.0