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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-bcb78493d1asm727760666b.39.2026.05.13.03.09.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 May 2026 03:09:49 -0700 (PDT) Date: Wed, 13 May 2026 11:09:48 +0100 From: David Laight To: Rodrigo Alencar <455.rodrigo.alencar@gmail.com> Cc: Andy Shevchenko , Andy Shevchenko , Jonathan Cameron , Rodrigo Alencar via B4 Relay , rodrigo.alencar@analog.com, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, David Lechner , Andy Shevchenko , Lars-Peter Clausen , Michael Hennerich , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Jonathan Corbet , Andrew Morton , Petr Mladek , Steven Rostedt , Rasmus Villemoes , Sergey Senozhatsky , Shuah Khan Subject: Re: [PATCH v12 02/11] lib: kstrtox: add kstrtoudec64() and kstrtodec64() Message-ID: <20260513110948.16db5243@pumpkin> In-Reply-To: References: X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) 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=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 13 May 2026 08:14:28 +0100 Rodrigo Alencar <455.rodrigo.alencar@gmail.com> wrote: > On 26/05/12 11:16PM, Andy Shevchenko wrote: > > On Tue, May 12, 2026 at 08:39:21PM +0100, Rodrigo Alencar wrote: ... > > Oh, I only now realised that this is sliding window for a single 64-bit signed value! > > I was under impression that you wanted implementation that covers 128-bit signed value > > (with 64 + 64)... > > So that was the initial approach with strntoull() with integer and fractional parts > combined in iio core. At that time I realized that we ended up combining them anyways > with: > > val64 = (u64)val * MICRO + val2 > > so why not have val64 already! And all this made me realise that once leading 0s are ok, > scale can be even bigger, e.g. > > scale = 20 > max = 0.09223372036854775807, min = -0.09223372036854775808 > scale = 21 > max = 0.009223372036854775807, min = -0.009223372036854775808 > > It might be a sliding window of 19 digits, but here we trade range for scale, precision > is still fixed at 64-bit. I wouldn't worry about that case unless it 'falls out in the wash'. > I have a new idea to make thing simpler, actually > it would go back to what David pointed out in the past. :-) -- David > Let me put this together... > > > > I am not representing -0.9999999999999999999 as is. The desired scale will have this > > > truncated. It may be -0.9999 or -0.999999 or -0.9. And this is practical for a > > > reasonable scale value... for pico and femto precision you still get a decent range. > > > > -- > > With Best Regards, > > Andy Shevchenko > > > > >