Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753913Ab2FKLFi (ORCPT ); Mon, 11 Jun 2012 07:05:38 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:53789 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753619Ab2FKLFf (ORCPT ); Mon, 11 Jun 2012 07:05:35 -0400 Date: Mon, 11 Jun 2012 12:05:17 +0100 From: Russell King - ARM Linux To: Liu Ying Cc: Liu Ying , g.liakhovetski@gmx.de, linux-fbdev@vger.kernel.org, FlorianSchandinat@gmx.de, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/3] mx3fb: do not support panning with fb blanked Message-ID: <20120611110517.GE11168@n2100.arm.linux.org.uk> References: <1339376810-8247-1-git-send-email-Ying.Liu@freescale.com> <20120611095102.GD11168@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2023 Lines: 51 On Mon, Jun 11, 2012 at 06:46:14PM +0800, Liu Ying wrote: > 2012/6/11, Russell King - ARM Linux : > > On Mon, Jun 11, 2012 at 09:06:48AM +0800, Liu Ying wrote: > >> This patch checks if framebuffer is unblanked before > >> we actually trigger panning in custom pan display > >> function. > >> > >> Signed-off-by: Liu Ying > >> --- > >> drivers/video/mx3fb.c | 5 +++++ > >> 1 files changed, 5 insertions(+), 0 deletions(-) > >> > >> diff --git a/drivers/video/mx3fb.c b/drivers/video/mx3fb.c > >> index e3406ab..d53db60 100644 > >> --- a/drivers/video/mx3fb.c > >> +++ b/drivers/video/mx3fb.c > >> @@ -1063,6 +1063,11 @@ static int mx3fb_pan_display(struct > >> fb_var_screeninfo *var, > >> dev_dbg(fbi->device, "%s [%c]\n", __func__, > >> list_empty(&mx3_fbi->idmac_channel->queue) ? '-' : '+'); > >> > >> + if (mx3_fbi->blank != FB_BLANK_UNBLANK) { > >> + dev_dbg(fbi->device, "panning with fb blanked not supported\n"); > >> + return -EFAULT; > >> + } > > > > Why is this an error, and why return -EFAULT? What userspace access > > failed? > > > Hi, Russell, > > IMHO, panning with framebuffer blanked is meaningless, at least, it is > not a common usecase. Yes, but why should anything in userspace care whether the display is blanked or not? For example, we may pan the display when a user program produces output, and we're on the last line of the display. We don't fail that just because the screen happens to be blank. So I don't see why we should actively fail an explicit userspace pan request just because the console happened to be blanked. What I'm basically saying is that as far as _userspace_ is concerned, all the standard APIs should just work as normal whether the display is blanked or not. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/