From mboxrd@z Thu Jan 1 00:00:00 1970 From: Abramo Bagnara Subject: Re: Re: About integer64 Date: Thu, 09 May 2002 15:25:34 +0200 Sender: alsa-devel-admin@lists.sourceforge.net Message-ID: <3CDA78CE.BE2D0F56@alsa-project.org> References: <200205091256.OAA26239@alsa.alsa-project.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Errors-To: alsa-devel-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: To: Paul Davis Cc: Jaroslav Kysela , alsa-devel@lists.sourceforge.net List-Id: alsa-devel@alsa-project.org Paul Davis wrote: > > >What I'm misunderstanding? I tend to interpret the former and the latter > >statements in a contradictory way. > > my reading of the "docs" (the Mac OS X driver and utilities) is that > RME haven't figured out a way to truncate the 64 bit fixed point > representation to a 32 bit integer using the Xilinx FPGA. they have > figured out how to render it as a 64 bit integer. so, they do the math > using a fixed point representation, then transform to 64 bit integer > when storing it in the register. the final part of the transform is > done by the host CPU, in our case up in user space since we can't do > float math conveniently in the kernel. > > does that make it clearer? Not very much: a) if 32 bit integer could be enough expressive, what's the problem to truncate it in your driver? b) if a 32 bit integer is not enough and a float is preferrable: considered that an ieee754 floating point is in the form (1+man)*2^exp what's the problem in converting it in your driver using ffs and some shift? With both way I don't see the two point you make: 1) why bother with signed vs unsigned 2) why use 64 bit integer Of course if a 64 bit integer is the best way to represent/report the value all is fine, but in this case I doubt that you don't have available the 64th bit for the sign. -- Abramo Bagnara mailto:abramo@alsa-project.org Opera Unica Phone: +39.546.656023 Via Emilia Interna, 140 48014 Castel Bolognese (RA) - Italy ALSA project http://www.alsa-project.org It sounds good! _______________________________________________________________ Have big pipes? SourceForge.net is looking for download mirrors. We supply the hardware. You get the recognition. Email Us: bandwidth@sourceforge.net