From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Use of 'reserved' fields in var_screeninfo Date: Mon, 14 Nov 2005 11:17:31 -0800 Message-ID: <4378E2CB.3080902@mvista.com> 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 1Ebjph-0001Js-Ec for linux-fbdev-devel@lists.sourceforge.net; Mon, 14 Nov 2005 11:17:37 -0800 Received: from gateway-1237.mvista.com ([12.44.186.158] helo=hermes.mvista.com) by mail.sourceforge.net with esmtp (Exim 4.44) id 1Ebjpf-0001lk-Sx for linux-fbdev-devel@lists.sourceforge.net; Mon, 14 Nov 2005 11:17:37 -0800 Received: from [127.0.0.1] (godzilla.mvista.com [10.0.0.2]) by hermes.mvista.com (Postfix) with ESMTP id 11FB71A9BC for ; Mon, 14 Nov 2005 11:17:32 -0800 (PST) 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 Hello, I've got a question about the purpose of the reserved fields in the var_screeninfo struct: struct fb_var_screeninfo { [ ... ] __u32 reserved[5]; /* Reserved for future compatibility */ }; What are these reserved for? Is it appropriate for drivers to use these for additional, HW-specific values that are then made available to the VSCREENINFO ioctls? If a driver does store state here, or attempt to pass info using an ioctl, the data is promptly overwritten by fbcon during an fbcon_switch(), when it creates a var_screeninfo struct, memsets it to zero, copies a couple fields and passes it to fb_set_var(). I have a patch to copy the 'reserved' fields during an fbcon_switch() that solves the problem but I'm not sure if this is the right thing to do. -- Kevin Hilman MontaVista Software -- http://www.mvista.com/ ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php