From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=192.198.163.11 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792497067; b=A3HEUo7Qyqjb5nh3JnocZ1jMH4hOLqD6IKjXLI/xruL4hIMGKe1qtllbUS01M+uG7GxK AosCFcpPaCRagWJemDdSfSbfT1Dq4GVuXPgaHOIC9gQg7dyaN8AhfyL7YkgqJJUNMQshU 1d9JaM+7BKWNFEIXy7QJtgookDLZlJfkTI9qISR3rhCPplvDRxwZw50X/7lj/EWVVnurs ovos+4SrYUdGYu2bdXC4sPioJy4JCft2C2ChO9CZ0+frrAEspqTs7VAZOerA7t+0VSDx6 s+4ECicc6lvLStYmWbu32jlJSWhLZj10dIhlNW3Lebn8PTGDvLqryVXhYoaNBxZWpsw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792497067; h=DMARC-Filter:DKIM-Signature:X-CSE-ConnectionGUID:X-CSE-MsgGUID: X-IronPort-AV:X-IronPort-AV:Received:X-CSE-ConnectionGUID: X-CSE-MsgGUID:X-ExtLoop1:X-IronPort-AV:Received:From:Date:To:cc: Subject:In-Reply-To:Message-ID:References:MIME-Version:Content-Type; bh=kjIus0/Z7THMqH+fmdFt+9x90O1BbsB0s2G1vUB5BlU=; b=4Ogf2OGx2fOpqiiZ/eIaaeHARC4cI6ofnmT3kOZEKKKN9L9/qLC9aEhj9cYPCM0ShahH 2lyxiAMvSaIuqyTamETZpFD+ShlySidmx9p+0QGxC45zHtymcIEju0VyXCOVP5NaXOpCR jXr7Fq+Uierfv8ELRZG75qi/vEMfrXnbFCnQOaRx/BrZVd+sj+QELYho3wEhYNAeX1hiI /6lIO9UAL8EMz1JfE1GkgYEz5eYyG71SUVdXcWz4Ry0A/69lZY6j+SbhyXA7sx+/wOYGz /mlCkvvrxO0skeimWQ+xwKptiPTSr7ZGH3KiPmHQEzTOnZZE7GSgPVVGCOghKY942EQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=lUwWStw7; arc=none smtp.remote-ip=192.198.163.11 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 41D74606A319; Tue, 20 Oct 2026 11:51:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 41D74606A319 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=lUwWStw7 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1792497068; x=1824033068; h=from:date:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=vZOZVuw0ZwLdXOpr1UleOlDXx5oOWBvkj4gsvs1vsuA=; b=lUwWStw708zBGMj1ZE8dkplhKeQnBnmoQ2vo6Nfp7SIFI5PaFv2h+gEC dtWslWb7whElHx8vp6K6NKc4TcnpelkICvInopLNbTtXp+2AynHM3NSQL AKps9D8L6YbUPWx7SVa8DaFhzGCazOpWH/i5SYibaqov44RK0PcIjGwNJ bnlm94NuvGmc6N6i2xuKJnf0mU3KmspHi4JjWYywJ1zKoy9LTx/KKuasS hmnBeIkbyphq0K1olPNe4SuJeMq2PVSXvA8BFjsCd9QNlM7df5hFCyfMs vhANBfB4sXBQGpMjAx7QukPIVLaxTtxq3f/ZPjDcPngc88+Qk5Go5SLMa w==; X-CSE-ConnectionGUID: 6wJtUXUrRLqCaGuzqKg1Qw== X-CSE-MsgGUID: U1Xu49YHSJqkHI+5RS94cg== X-IronPort-AV: E=McAfee;i="6800,10657,11940"; a="1098546" X-IronPort-AV: E=Sophos;i="6.27,168,1787036400"; d="scan'208";a="1098546" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2026 04:51:07 -0700 X-CSE-ConnectionGUID: Rgz5036KQxSUgIH5S/JUhg== X-CSE-MsgGUID: lWP5tft+RLebTMNLYPQWxA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,168,1787036400"; d="scan'208";a="2852905" Received: from ijarvine-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.244.181]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2026 04:50:59 -0700 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Date: Tue, 20 Oct 2026 14:50:53 +0300 (EEST) To: Andy Shevchenko cc: Jiri Slaby , Vinicius Pedrosa , linux-serial , Greg Kroah-Hartman , robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, devicetree@vger.kernel.org, LKML , linux-sunxi@lists.linux.dev, Andre Przywara , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , Enzo Adriano Subject: Re: [PATCH v2 2/4] serial: 8250_dw: Only accept a contiguous DLF readback In-Reply-To: Message-ID: <09812a6a-dd0d-9c47-e1ad-5220f1954648@linux.intel.com> References: X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Tue, 20 Oct 2026, Andy Shevchenko wrote: > On Tue, Oct 20, 2026 at 08:11:06AM +0200, Jiri Slaby wrote: > > On 19. 10. 26, 22:06, Vinicius Pedrosa wrote: > > ... > > > > - if (reg) { > > > + /* > > > + * DLF is a bit field starting at bit 0, so a real one reads back as > > > + * 2^n - 1. Any other value means this offset is something else. > > > + */ > > > + if (reg && !(reg & (reg + 1))) { > > > > Do I understand correctly, that this equivalent to: > > if (is_power_of_2(reg + 1)) > > ? > > Yes, and since we check for reg to be "not zero", this will work the rest. For is_power_of_2(), 0 is not a power of two. And it also wouldn't make sense to have zero bits in the bit field as it's same as no bit field so using just is_power_of_2() should be enough. It could be that's what Andy meant, but the wording left too much room for interpretation. -- i.