From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Schoenebeck Subject: basic FB development questions Date: Wed, 23 Apr 2008 00:50:30 +0200 Message-ID: <200804230050.31349.cuse@users.sourceforge.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1JoRK1-0003tp-CZ for linux-fbdev-devel@lists.sourceforge.net; Tue, 22 Apr 2008 15:50:45 -0700 Received: from dns1.rz.hs-heilbronn.de ([141.7.1.18]) by mail.sourceforge.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.44) id 1JoRJz-0004ek-Ji for linux-fbdev-devel@lists.sourceforge.net; Tue, 22 Apr 2008 15:50:45 -0700 Received: from fry.software-engineering.org ([141.7.66.13]) by dns1.rz.hs-heilbronn.de (8.14.1/8.14.1) with ESMTP id m3MMoaTh011693 for ; Wed, 23 Apr 2008 00:50:36 +0200 (CEST) Received: from host391.homenet.telecomitalia.it (host2-28-static.38-79-b.business.telecomitalia.it [79.38.28.2]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by fry.software-engineering.org (Postfix) with ESMTP id 77FAC487A8 for ; Wed, 23 Apr 2008 00:41:14 +0200 (CEST) Content-Disposition: inline List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-fbdev-devel-bounces@lists.sourceforge.net Errors-To: linux-fbdev-devel-bounces@lists.sourceforge.net To: linux-fbdev-devel@lists.sourceforge.net Hi! I'm currently writing a Linux FB driver for an USB LCD. I've written Linux drivers before, but not a FB driver yet, so I hope you can help me with some basic FB development questions. First of all, AFAIK most FB drivers are based upon memory mapped IO, right? But in my case the graphics are forwarded via calls of Linux's USB subsystem. Which FB approach would suggest in this case? Something like the virtual framebuffer driver with some kind of static allocated buffer? If yes, what kind of function would I have to implement to trigger the screen sync between that modified buffer and the hardware (that is sending the buffer's data via USB to the device)? Or should I implement mmap? I mean: I know everything about the USB side to recognize the device and sending data etc., I just don't know how to establish a FB callback or something to "flush" the suggested graphics buffer. In the "fb_var_screeninfo" struct there are the following members which I'm not sure about their precise purpose: * "pixclock": is that the average speed (in ps) with which one pixel of the screen is changed? * "left_margin", "right_margin", "upper_margin", "lower_margin": I'm confused about these members, I first thought that would be some kind of reference margin (in pixels), but the header file says those are timing values? * "hsync_len", "vsync_len": what's that exactly and is it a timing or pixel value? If there are basic docs about FB terms etc, please let me know! Thanks for any help! CU Christian ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone