From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755773Ab3HFP2n (ORCPT ); Tue, 6 Aug 2013 11:28:43 -0400 Received: from mail-ob0-f173.google.com ([209.85.214.173]:38678 "EHLO mail-ob0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753590Ab3HFP2l (ORCPT ); Tue, 6 Aug 2013 11:28:41 -0400 MIME-Version: 1.0 X-Originating-IP: [178.83.130.250] In-Reply-To: <1375791502.4276.38.camel@weser.hi.pengutronix.de> References: <1374772648-19151-1-git-send-email-tom.cooksey@arm.com> <51f29ccd.f014b40a.34cc.ffffca2aSMTPIN_ADDED_BROKEN@mx.google.com> <51ffdc7e.06b8b40a.2cc8.0fe0SMTPIN_ADDED_BROKEN@mx.google.com> <1375791502.4276.38.camel@weser.hi.pengutronix.de> Date: Tue, 6 Aug 2013 17:28:40 +0200 X-Google-Sender-Auth: brnB2gPkPaSBqw162ZcBIJ5Kdso Message-ID: Subject: Re: [Linaro-mm-sig] [RFC 0/1] drm/pl111: Initial drm/kms driver for pl111 From: Daniel Vetter To: Lucas Stach Cc: Tom Cooksey , Linux Fbdev development list , Pawel Moll , Linux Kernel Mailing List , dri-devel , "linaro-mm-sig@lists.linaro.org" , "linux-arm-kernel@lists.infradead.org" , "linux-media@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 6, 2013 at 2:18 PM, Lucas Stach wrote: > I strongly disagree with exposing low-level hardware details like tiling > to userspace. If we have to do the negotiation of those things in > userspace we will end up with having to pipe those information through > things like the wayland protocol. I don't see how this could ever be > considered a good idea. > > I would rather see kernel drivers negotiating those things at dmabuf > attach time in way invisible to userspace. I agree that this negotiation > thing isn't easy to get right for the plethora of different hardware > constraints we see today, but I would rather see this in-kernel, where > we have the chance to fix things up if needed, than in a fixed userspace > interface. The problem with negotiating tiling in the kernel for at least drm/i915 is that userspace needs to know the tiling and for allocating actually be in charge of it. The approach used by prime thus far is to simply use linear buffers between different gpus. If you want something better I guess you need to have a fairly tightly integrate userspace driver, so I don't see how passing around the tiling information should be an issue for those cases. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-oa0-f54.google.com ([209.85.219.54]:41243 "EHLO mail-oa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755429Ab3HFP2l (ORCPT ); Tue, 6 Aug 2013 11:28:41 -0400 Received: by mail-oa0-f54.google.com with SMTP id o6so987817oag.41 for ; Tue, 06 Aug 2013 08:28:40 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1375791502.4276.38.camel@weser.hi.pengutronix.de> References: <1374772648-19151-1-git-send-email-tom.cooksey@arm.com> <51f29ccd.f014b40a.34cc.ffffca2aSMTPIN_ADDED_BROKEN@mx.google.com> <51ffdc7e.06b8b40a.2cc8.0fe0SMTPIN_ADDED_BROKEN@mx.google.com> <1375791502.4276.38.camel@weser.hi.pengutronix.de> Date: Tue, 6 Aug 2013 17:28:40 +0200 Message-ID: Subject: Re: [Linaro-mm-sig] [RFC 0/1] drm/pl111: Initial drm/kms driver for pl111 From: Daniel Vetter To: Lucas Stach Cc: Tom Cooksey , Linux Fbdev development list , Pawel Moll , Linux Kernel Mailing List , dri-devel , "linaro-mm-sig@lists.linaro.org" , "linux-arm-kernel@lists.infradead.org" , "linux-media@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-media-owner@vger.kernel.org List-ID: On Tue, Aug 6, 2013 at 2:18 PM, Lucas Stach wrote: > I strongly disagree with exposing low-level hardware details like tiling > to userspace. If we have to do the negotiation of those things in > userspace we will end up with having to pipe those information through > things like the wayland protocol. I don't see how this could ever be > considered a good idea. > > I would rather see kernel drivers negotiating those things at dmabuf > attach time in way invisible to userspace. I agree that this negotiation > thing isn't easy to get right for the plethora of different hardware > constraints we see today, but I would rather see this in-kernel, where > we have the chance to fix things up if needed, than in a fixed userspace > interface. The problem with negotiating tiling in the kernel for at least drm/i915 is that userspace needs to know the tiling and for allocating actually be in charge of it. The approach used by prime thus far is to simply use linear buffers between different gpus. If you want something better I guess you need to have a fairly tightly integrate userspace driver, so I don't see how passing around the tiling information should be an issue for those cases. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Date: Tue, 06 Aug 2013 15:28:40 +0000 Subject: Re: [Linaro-mm-sig] [RFC 0/1] drm/pl111: Initial drm/kms driver for pl111 Message-Id: List-Id: References: <1374772648-19151-1-git-send-email-tom.cooksey@arm.com> <51f29ccd.f014b40a.34cc.ffffca2aSMTPIN_ADDED_BROKEN@mx.google.com> <51ffdc7e.06b8b40a.2cc8.0fe0SMTPIN_ADDED_BROKEN@mx.google.com> <1375791502.4276.38.camel@weser.hi.pengutronix.de> In-Reply-To: <1375791502.4276.38.camel@weser.hi.pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Lucas Stach Cc: Tom Cooksey , Linux Fbdev development list , Pawel Moll , Linux Kernel Mailing List , dri-devel , "linaro-mm-sig@lists.linaro.org" , "linux-arm-kernel@lists.infradead.org" , "linux-media@vger.kernel.org" On Tue, Aug 6, 2013 at 2:18 PM, Lucas Stach wrote: > I strongly disagree with exposing low-level hardware details like tiling > to userspace. If we have to do the negotiation of those things in > userspace we will end up with having to pipe those information through > things like the wayland protocol. I don't see how this could ever be > considered a good idea. > > I would rather see kernel drivers negotiating those things at dmabuf > attach time in way invisible to userspace. I agree that this negotiation > thing isn't easy to get right for the plethora of different hardware > constraints we see today, but I would rather see this in-kernel, where > we have the chance to fix things up if needed, than in a fixed userspace > interface. The problem with negotiating tiling in the kernel for at least drm/i915 is that userspace needs to know the tiling and for allocating actually be in charge of it. The approach used by prime thus far is to simply use linear buffers between different gpus. If you want something better I guess you need to have a fairly tightly integrate userspace driver, so I don't see how passing around the tiling information should be an issue for those cases. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch From mboxrd@z Thu Jan 1 00:00:00 1970 From: daniel@ffwll.ch (Daniel Vetter) Date: Tue, 6 Aug 2013 17:28:40 +0200 Subject: [Linaro-mm-sig] [RFC 0/1] drm/pl111: Initial drm/kms driver for pl111 In-Reply-To: <1375791502.4276.38.camel@weser.hi.pengutronix.de> References: <1374772648-19151-1-git-send-email-tom.cooksey@arm.com> <51f29ccd.f014b40a.34cc.ffffca2aSMTPIN_ADDED_BROKEN@mx.google.com> <51ffdc7e.06b8b40a.2cc8.0fe0SMTPIN_ADDED_BROKEN@mx.google.com> <1375791502.4276.38.camel@weser.hi.pengutronix.de> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Aug 6, 2013 at 2:18 PM, Lucas Stach wrote: > I strongly disagree with exposing low-level hardware details like tiling > to userspace. If we have to do the negotiation of those things in > userspace we will end up with having to pipe those information through > things like the wayland protocol. I don't see how this could ever be > considered a good idea. > > I would rather see kernel drivers negotiating those things at dmabuf > attach time in way invisible to userspace. I agree that this negotiation > thing isn't easy to get right for the plethora of different hardware > constraints we see today, but I would rather see this in-kernel, where > we have the chance to fix things up if needed, than in a fixed userspace > interface. The problem with negotiating tiling in the kernel for at least drm/i915 is that userspace needs to know the tiling and for allocating actually be in charge of it. The approach used by prime thus far is to simply use linear buffers between different gpus. If you want something better I guess you need to have a fairly tightly integrate userspace driver, so I don't see how passing around the tiling information should be an issue for those cases. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch