From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 15 Dec 2014 11:02:13 +0100 From: Nikolaus Schulz To: Hartmut Knaack Cc: Jonathan Cameron , Lars-Peter Clausen , Peter Meerwald , Grant Likely , Rob Herring , Michael Welling , Philippe Reynes , linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, devicetree@vger.kernel.org, Alban Bedel Subject: Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554 Message-ID: <20141215100213.GA6159@avionic-0071.adnet.avionic-design.de> References: <1416858614-32265-1-git-send-email-nikolaus.schulz@avionic-design.de> <1416858614-32265-2-git-send-email-nikolaus.schulz@avionic-design.de> <5482EA33.7020305@gmx.de> <20141212155804.GA1142@avionic-0071.adnet.avionic-design.de> <548C209A.7000904@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <548C209A.7000904@gmx.de> List-ID: On Sat, Dec 13, 2014 at 12:18:50PM +0100, Hartmut Knaack wrote: > Nikolaus Schulz schrieb am 12.12.2014 um 16:58: > > On Sat, Dec 06, 2014 at 12:36:19PM +0100, Hartmut Knaack wrote: > >> Nikolaus Schulz schrieb am 24.11.2014 um 20:50: > >>> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with a= n SPI > >>> interface. [dac8554_probe:] > >>> + st->vref_mv =3Doltage_uv / 1000; > >> How hard do you want to depend on a voltage regulator? Doing regulat= or_get_voltage() > >> could even be called dynamically in _read_raw(), making a real regul= ator optional. > >=20 > > Hmm. I understand that the DAC voltage input may not be provided by a > > regulator, but is that a common scenario? No other DAC driver I look= ed > > at handles that case, they all consider it an error if the regulator = is > > absent. > >=20 > I had people in mind, who might want to use such DAC with one of the po= pular > embedded boards like Raspberry Pi - people who would just like to "plug= and > play" without the need or ability to build a kernel (or would prefer to= go > with the convenience of a distribution kernel). But since you've put a > dependency on OF, I don't see a way to use this device with a stock dis= tribution > kernel anyway. As long as the kernel supports devicetree, compiling the module and a new DT blob should be enough to enable support for the DAC8554. And, as Jonathan has pointed out, if there is no real regulator providing the input current, a fixed regulator can be added to the DT. > But I still think that calculating the actual voltage during _read_raw(= ) would > be a good idea, as there is support for regulators providing different = voltages, > which can be changed during runtime. Agreed. --=20 Avionic Design GmbH Nikolaus Schulz Wragekamp 10 D-22397 Hamburg Germany Tel.: +49 40 88187-163 Fax: +49 40 88187-150 Email: nikolaus.schulz@avionic-design.de Avionic Design GmbH Amtsgericht Hamburg HRB 82598 Gesch=E4ftsf=FChrung: Cornelis Broers Ust.-Ident-Nr.: DE813378254