From mboxrd@z Thu Jan 1 00:00:00 1970 From: Antonino Daplas Subject: Re: Framebuffer with banked memory Date: 31 Oct 2002 08:36:08 +0800 Sender: linux-fbdev-devel-admin@lists.sourceforge.net Message-ID: <1036024565.808.27.camel@daplas> References: <20021030104922.6612.qmail@web14206.mail.yahoo.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Received: from [203.167.79.9] (helo=willow.compass.com.ph) by usw-sf-list1.sourceforge.net with esmtp (Exim 3.31-VA-mm2 #1 (Debian)) id 1873OO-000367-00 for ; Wed, 30 Oct 2002 16:41:01 -0800 Received: from AP-202-70-99-53.compass.com.ph (AP-202-70-99-53.compass.com.ph [202.70.99.53]) by willow.compass.com.ph (8.9.3/8.9.3) with ESMTP id IAA27914 for ; Thu, 31 Oct 2002 08:40:57 +0800 (PHT) (envelope-from adaplas@pol.net) In-Reply-To: <20021030104922.6612.qmail@web14206.mail.yahoo.com> Errors-To: linux-fbdev-devel-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Id: List-Unsubscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" To: fbdev On Wed, 2002-10-30 at 18:49, alain volmat wrote: > Hi, > > As I said the video card I am now writing a > framebuffer for, doesn't have linear memory, which > means that I can only access a small part of the > memory at a time and then set offset registers in > order to access another part of the memory. > > I would like to know if there is such case in current > framebuffer drivers ?? If so, what is the common > solution to do that ?? None in the current drivers. > > In fact the problem remains in the case of mmap (which > is the most common ;( of course), since the memory > seams to be accessed directly by pointer, there might > be no wait to detect if we need to set or not an > offset. In case of fb_read fb_write, it is possible to > do that before the actual write at the end (even if it > is not sooo beautiful ... ). The safest solution is to create custom fb_write? and fb_read? routines. Maybe James will add these hooks for hardware like yours. Then disallow mmap's except probably for the MMIO regions. Creating a bank-switching mechanism, besides entailing a lot of work, is not entirely safe. Tony PS: What's your hardware? ------------------------------------------------------- This sf.net email is sponsored by: Influence the future of Java(TM) technology. Join the Java Community Process(SM) (JCP(SM)) program now. http://ads.sourceforge.net/cgi-bin/redirect.pl?sunm0004en