From nobody Thu Nov 21 21:32:59 2024 Received: from layka.disroot.org (layka.disroot.org [178.21.23.139]) (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 DDB641E0DFC; Mon, 18 Nov 2024 19:26:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.21.23.139 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731957978; cv=none; b=Uxmzaszntv940lnE/b8SAaDv86mr0hR6q21V2rYtFhytaipQWca9fbPt2nHM789L1r69VkfxAQGZ8DJaLFBiBGYoKN0EEZXFt/cSbOLpgPBqX6g71fKINrHQhIAKWSKUdZsnLLQth2zOo5PtguKC6JpWD2ny2vUZxX8yfkHBDv8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731957978; c=relaxed/simple; bh=/kpCaNpWSefaUOtO8wO0x3ZwJqhUXDDfTytqZYILjYI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=RTEiLZXcA3BIOD37zDo1ACjuWlT0b04qO1vidorpwCCEkxyIcj0QsfnzLN1yrnJRHBBYzQUWSfD391QX2v0MmV7QpEEre6kEq5Nph5A1ow05HKGC3cfXuTJia7KhTR+wQ9XSMntZMDvZq6XmHOOIliocQvaFDLfkIXm+xhzmRm8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=disroot.org; spf=pass smtp.mailfrom=disroot.org; dkim=pass (2048-bit key) header.d=disroot.org header.i=@disroot.org header.b=HZ+7KNbZ; arc=none smtp.client-ip=178.21.23.139 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=disroot.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=disroot.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=disroot.org header.i=@disroot.org header.b="HZ+7KNbZ" Received: from mail01.disroot.lan (localhost [127.0.0.1]) by disroot.org (Postfix) with ESMTP id 1633F2523D; Mon, 18 Nov 2024 20:26:13 +0100 (CET) X-Virus-Scanned: SPAM Filter at disroot.org Received: from layka.disroot.org ([127.0.0.1]) by localhost (disroot.org [127.0.0.1]) (amavis, port 10024) with ESMTP id 7PIE06jNsvOy; Mon, 18 Nov 2024 20:26:12 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=disroot.org; s=mail; t=1731957972; bh=/kpCaNpWSefaUOtO8wO0x3ZwJqhUXDDfTytqZYILjYI=; h=From:To:Cc:Subject:Date; b=HZ+7KNbZuciHfqIRHm6J20HHExa69IOA/9P2Nj55VC2MTk8JiUcAKs8pPCSLs3K2q aXy3z21plgViAP20OypA7vAlbDRDOSvpHL2bG2zavukWyJ4A1s1dCrpgPUQZ/eXb6d iNKlKbj9pxBtJ3Hdo7FkzLaXUioLwSm3yyTUHxpzl5adQoCON2uAD3NruK6D5Fwmcj UTo0ghh7W32tj2Niq7nHpK0fUQcdSoNcGdh+YQUDpplt0OGWqJUS0nGkd0Gag5awgc gdnLP/tcaQ1CHe4xIWM6MZt9SktJF5RDeSDZHX5A49D41IMjnNT6a93A5ajtc/0l6g 7Ygp+XAaiX1Ag== From: Yao Zi To: Jonathan Corbet , Michael Turquette , Stephen Boyd Cc: Yao Zi , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] docs: clk: describe userspace debugging facilities Date: Mon, 18 Nov 2024 19:25:27 +0000 Message-ID: <20241118192526.44180-2-ziyao@disroot.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Starting from commit 03111b1088f1 ("clk: Add support for enabling/disabling clocks from debugfs"= ), it's possible to operate clocks from userspace through debugfs for testing purpose. This feature isn't provided as a Kconfig but rather a macro in source for security consideration, thus is hard to find. Let's document the macro to ease everyone's life of clock debugging. Signed-off-by: Yao Zi --- Documentation/driver-api/clk.rst | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/Documentation/driver-api/clk.rst b/Documentation/driver-api/cl= k.rst index 93bab5336dfd..1787c07e8e19 100644 --- a/Documentation/driver-api/clk.rst +++ b/Documentation/driver-api/clk.rst @@ -310,3 +310,11 @@ driver in that case. Note that locking must also be considered when code outside of the common clock framework needs to access resources used by the clock operations. Th= is is considered out of scope of this document. + +Debug in Userspace +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +The common clk framework creates read-only debugfs entries at +``/sys/kernel/debug/clk``. For test and debug purpose, you could define +``CLOCK_ALLOW_WRITE_DEBUGFS`` in ``drivers/clk/clk.c`` to make them writab= le. +This may cause security problems and should *NEVER* be enabled on producti= on. --=20 2.47.0