From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rolf Offermanns Subject: Re: color map vs. pseudo-palette vs. RAMDAC registers Date: Mon, 24 Oct 2005 13:01:16 +0200 Message-ID: <200510241301.17275.rolf@offermanns.de> References: <200510240948.50185.rolf.offermanns@gmx.net> Reply-To: linux-fbdev-devel@lists.sourceforge.net Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1EU05B-0003nK-CA for linux-fbdev-devel@lists.sourceforge.net; Mon, 24 Oct 2005 04:01:37 -0700 Received: from mail.sysgo.com ([62.8.134.5]) by mail.sourceforge.net with esmtp (Exim 4.44) id 1EU05A-00039P-U8 for linux-fbdev-devel@lists.sourceforge.net; Mon, 24 Oct 2005 04:01:37 -0700 In-Reply-To: Content-Disposition: inline Sender: linux-fbdev-devel-admin@lists.sourceforge.net Errors-To: linux-fbdev-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" To: linux-fbdev-devel@lists.sourceforge.net Cc: Geert Uytterhoeven On Monday 24 October 2005 09:57, Geert Uytterhoeven wrote: > > -------------------------------------------------------------------- > > Pseudocolor: > > * cmap is not used > > That should be `pseudo palette is not used'. > > > * DAC[X] is programmed to (red, green, blue) > > -------------------------------------------------------------------- > > Does that mean, I do not need to allocate a color map, if my driver would > > only > > It means you don't have to fill in the pseudo palette in this mode. OK. > > support pseudocolor visual? Is pseudocolor always used for 8bpp or are > > there situations where 16bpp pseudocolor makes sense? > > Pseudocolor is not always 8 bpp (1, 2, 4 are common values as well), but > large values are very uncommon, since 16 bpp pseudocolor would mean a > 65536-entries colormap. OK. > > ------------------------------------------------------------------------- > >---- Truecolor: > > * does not use RAMDAC (usually has 3 of them). > > * var->{color}.offset contains start of bitfield > > * var->{color}.length contains length of bitfield > > * cmap is programmed to (red << red.offset) | > > (green << green.offset) | > > (blue << blue.offset) | > > (transp << transp.offset) > > * RAMDAC does not exist > > ------------------------------------------------------------------------- > >---- Now I am lost: > > -> does not use RAMDAC. > > I understand this. It states the same in my chip reference. But what > > means "usually has 3 of them" in this context? > > Red, green, and blue. OK. But this is for H/W with DirectColor support where each color has its own CLUT, right? > > -> cmap is programmed to... > > In the code that follows this comment, not the cmap is programmed, but > > the pseudo palette. > > That should be `pseudo palette' again. OK. > > > 1. Why do I need a pseudo palette and where does its size 16 comes from? > > It's used to translate from the 16 text console colors to actual pixel > values. OK, and these 16 color can be set/defined by text mode apps, right? Thanks for these explanations Gerd. Shall I provide a patch for the skeletonfb driver comments? The one thing, I still do not understand is: What are color maps used for in the different visuals? In pseudo mode they are not used at all. In TrueColor mode there should be no need to map anything? I checked the documentation again, but there must be something I have overread. Could you please explain this? Thanks, Rolf ------------------------------------------------------- This SF.Net email is sponsored by the JBoss Inc. Get Certified Today * Register for a JBoss Training Course Free Certification Exam for All Training Attendees Through End of 2005 Visit http://www.jboss.com/services/certification for more information