From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: Re: newbie: fb specs and indirect VRAM access Date: Thu, 21 Aug 2008 14:54:19 +0200 (CEST) Message-ID: References: <47858.200.178.190.130.1219177894.squirrel@mail2.icmc.usp.br> <34825.200.178.190.130.1219322627.squirrel@mail2.icmc.usp.br> 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 1KW9gJ-0008I7-O3 for linux-fbdev-devel@lists.sourceforge.net; Thu, 21 Aug 2008 05:54:27 -0700 Received: from monty.telenet-ops.be ([195.130.132.56]) by mail.sourceforge.net with esmtp (Exim 4.44) id 1KW9gH-0002Jy-3x for linux-fbdev-devel@lists.sourceforge.net; Thu, 21 Aug 2008 05:54:27 -0700 In-Reply-To: <34825.200.178.190.130.1219322627.squirrel@mail2.icmc.usp.br> 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: Jorge Marques Pelizzoni Cc: linux-fbdev-devel@lists.sourceforge.net On Thu, 21 Aug 2008, Jorge Marques Pelizzoni wrote: > A few days ago I sent the message below asking about framebuffer device > documentation and explaining my specific situation. Nobody aswered and I > wonder why. If those are not questions for this list, can someone please > redirect me to the right forum? I had hoped somebody else would find time to respond ;-) > Jorge Marques Pelizzoni escreveu: > > I am considering implementing a frame buffer device for a mobile platform > > (LPC2400 on uCLinux) that, as far as I can tell, seems to lack one. Well, > > I am a newbie to all things frame buffer-related (though familiar with > > kernel/device module implementation) and would most appreciate it if you > > could answer the following questions: > > > > 1 - are there documents specifying frame buffer devices and how > > applications are expected to handle them (in short, their API)? linux/Documentation/fb/framebuffer.txt linux/include/linux/fb.h > > 2 - my CPU cannot address "real" VRAM directly, all control being carried > > out by means of a parallel interface. I gathered that an fb user is > > expected to write to (virtual) VRAM directly via a pointer provided by the > > driver and never notifies the driver of changes. Have you seen such a > > set-up before and do you think these requirements can be reconciled? The > > only way round this I can currently see is making the driver periodically > > check the virtual VRAM for changes and transmit only changed parts. All in > > all, a costly operation, as everything must be carried out by the same > > CPU. Could whatever is used to implement mmap be called into play (without > > whatever is used to implement msync)? linux/Documentation/fb/deferred_io.txt 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 Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/