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a="1262071" X-IronPort-AV: E=Sophos;i="6.27,169,1787036400"; d="scan'208";a="1262071" Received: from fmviesa013.fm.intel.com ([10.60.135.153]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2026 23:43:29 -0700 X-CSE-ConnectionGUID: EUWzumZPRr2YHD64Lu80qw== X-CSE-MsgGUID: 1d1oD7PaRWOdxkHTs7rzWg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,169,1787036400"; d="scan'208";a="4810152" Received: from cpetruta-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.245.24]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2026 23:43:26 -0700 Date: Wed, 21 Oct 2026 09:43:23 +0300 From: Andy Shevchenko To: Ilpo =?iso-8859-1?Q?J=E4rvinen?= Cc: Vinicius Pedrosa , Jiri Slaby , 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@arm.com, wens@kernel.org, jernej.skrabec@gmail.com, samuel@sholland.org, enzo.adriano.code@gmail.com Subject: Re: [PATCH v2 2/4] serial: 8250_dw: Only accept a contiguous DLF readback Message-ID: References: <09812a6a-dd0d-9c47-e1ad-5220f1954648@linux.intel.com> <20261020122746.41699-1-vinicius.eduardo.pedrosa@gmail.com> <6c4a5613-7e10-64dc-a670-6407a4f1f6ed@linux.intel.com> X-Mailing-List: linux-kernel@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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6c4a5613-7e10-64dc-a670-6407a4f1f6ed@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo On Tue, Oct 20, 2026 at 04:02:29PM +0300, Ilpo Järvinen wrote: > On Tue, 20 Oct 2026, Vinicius Pedrosa wrote: > > On Tue, 20 Oct 2026, Ilpo Järvinen wrote: > > > > > 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. > > > > I think the reg != 0 check still needs to stay here, since the test is > > is_power_of_2(reg + 1), rather than is_power_of_2(reg). > > > > For reg == 0, reg + 1 is 1, and is_power_of_2(1) is true. So without > > the explicit reg check, a zero readback, meaning no DLF, would be > > accepted as a valid DLF. > > > > I'll keep it as: > > > > reg && is_power_of_2(reg + 1) > > > > in v3. > > Ah, you're right. Sorry for being unclear, yes, that's what I meant, reg != 0 should stay. -- With Best Regards, Andy Shevchenko