From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: Re: basic FB development questions Date: Wed, 23 Apr 2008 11:01:57 +0200 (CEST) Message-ID: References: <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-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1JoarZ-0007Ei-LI for linux-fbdev-devel@lists.sourceforge.net; Wed, 23 Apr 2008 02:02:01 -0700 Received: from monty.telenet-ops.be ([195.130.132.56]) by mail.sourceforge.net with esmtp (Exim 4.44) id 1JoarY-0007d2-Jf for linux-fbdev-devel@lists.sourceforge.net; Wed, 23 Apr 2008 02:02:01 -0700 In-Reply-To: <200804230050.31349.cuse@users.sourceforge.net> 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: Christian Schoenebeck Cc: linux-fbdev-devel@lists.sourceforge.net On Wed, 23 Apr 2008, Christian Schoenebeck wrote: > 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. Documentation/fb/deferred_io.txt > 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? It's the inverse of the dot clock (in Hz). > * "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! Documentation/fb/framebuffer.txt, section 5. Video Mode Timings. But if your screen is 100% digital, they may not matter at all, and zeroes are OK for the margins and sync lengths. IIRC, fbset doesn't like pixclock being zero, so you should fill in something. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds ------------------------------------------------------------------------- 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