Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hello Maxime, Maxime Ripard wrote: > Hi, > > On Thu, Feb 16, 2017 at 01:28:24PM +0100, Tobias Jakobi wrote: >> Hello, >> >> I'm not sure if I'm missing something here, but I don't see how this is >> supposed to work. >> >> This just multiplies the height of the drm_mode_fb_cmd2 object with the >> number of buffers. Let's say I have width=1024, height=768, then now I >> have a framebuffer which has height=2304 (in the num_buffers=3 case). At >> some point this FB is set as the primary plane, giving us a 1024x2304 >> mode. I don't think that this is intended. >> >> In my opinion this multi-buffer thing should touch drm_mode_fb_cmd2 at >> all. The underlying BO should be larger, but not the FB itself. If this >> is supposed to work, then the fbdev helpers should create as many FBs as >> there are buffers, and then offset each of these FB into the BO. > > This only increases the virtual resolution, not the visible one. hmm, OK, I guess I need to test this again then. The last time I checked such an approach was on vanilla-4.7.y IIRC. And there it failed miserably. >> What I'm also not seeing is code that handles the fbdev's virtual >> resolutions. After all num_buffers should only increase those. Same for >> the panning ioctl(). > > This is already implemented through drm_fb_helper_pan_display. Thanks, I'll take a look! With best wishes, Tobias > > Maxime > ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi Maxime, On Wednesday 15 Feb 2017 13:51:29 Maxime Ripard wrote: > On Tue, Feb 14, 2017 at 11:25:08PM +0200, Laurent Pinchart wrote: > > On Tuesday 14 Feb 2017 21:09:51 Daniel Vetter wrote: > >> On Mon, Feb 13, 2017 at 11:20:51AM +, Daniel Stone wrote: > >>> On 13 February 2017 at 10:54, Maxime Ripard wrote: > On Sun, Feb 12, 2017 at 02:28:11PM +0200, Laurent Pinchart wrote: > > On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: > >> This patch add a config to support to create multi buffer for cma > >> fbdev. Such as double buffer and triple buffer. > >> > >> Cma fbdev is convient to add a legency fbdev. And still many > >> Android devices use fbdev now and at least double buffer is needed > >> for these Android devices, so that a buffer flip can be operated. It > >> will need some time for Android device vendors to abondon legency > >> fbdev. So multi buffer for fbdev is needed. > > > > How exactly do we expect Android to move away from fbdev if we add > > features to the fbdev compat layer ? I'd much rather make it clear > > to them that fbdev is a thing from the past and that they'd better > > migrate now. > > If your point is that merging this patch will slow down the Android > move away from fbdev, I disagree with that (obviously). > > I don't care at all about Android on my platform of choice, but don't > see how that merging this patch will change anything. > > Let's be honest, Android trees typically have thousands of patches on > top of mainline. Do you think a simple, 15 LoC, patch will make any > difference to vendors? If they want to stay on fbdev and have that > feature, they'll just merge this patch, done. > >>> > >>> So, in that case, why not just let them do that? They'd already have > >>> to add patches to use this, surely; we don't have anything in mainline > >>> kernels which allows people to actually use this larger allocation. > >>> Apart from software mmap() and using panning to do flips, but I'm > >>> taking it as a given that people shipping Android on their devices > >>> aren't using software rendering. > >> > >> I think we need to make a distinction between fbdev the subsystem in the > >> kernel, and fbdev the uabi: > >> > >> - fbdev the subsystem is completely dead in upstream. I think we have > >> full agreement on that. > >> > >> - fbdev the uabi isn't, and if we can get more users from fbdev based > >> drivers to kms/atomic drivers by adding fairly simple stuff like this, > >> I'm all for it. > > > > The real question, in my opinion, is how to get more users for the DRM/KMS > > userspace API, to help killing the fbdev API. What's the incentive for > > userspace to migrate if we tell them that we're going to support the fbdev > > API forever, and will even go through the trouble of extending the > > supported feature set ? I have a customer who wouldn't have migrated > > their userspace to DRM/KMS if these two patches had been merged a few > > years ago. > > If those patches are not in, then I can see three ways to support old > / deficient userspaces: > 1) Carry those patches out of tree > 2) Write an fbdev driver for the display engine > 3) Rewrite the userspace components > > While 3. would arguably be the best option, this isn't always one, > unfortunately. I agree that it's not a solution that can be deployed overnight, but it's clearly what we all (as in kernel community and system vendors) need to head towards. > And as a community, I think 1 and 2 are not very good for us. 1. will > drive away vendors from our community, undermining the effort we've > been doing for a few years. And 2 will result in a driver we really > don't want to merge (so useless), and even if it would out of tree, > that would make it one less system / board / SoC *with* DRM/KMS APIs, > reducing the interest of switching for application developpers. > > If we really want to make people switch to DRM / KMS, we have to make > it ubiquitous. And if we want to make it ubiquitous, we really want to > have a transition period where people will have both APIs, supported > in a decent enough way. Haven't we had such a grace period already, until the fbdev subsystem stopped accepting new drivers ? It has hardly been an overnight switch. > And then, that's a win for everyone, because in the process you get > fbdev (booo!) and KMS (yay!), allowing for people to switch over, and > eventually kill the emulation entirely. But it's far too early for > that. I mean, we don't even have an fbv replacement yet... We're talking about http://s-tech.elsat.net.pl/fbv/, whose latest release dates from 2011 ? :-) https://github.com/tomba/kmsxx/blob/master/utils/kmsview.cpp It won't be hard to add support for BMP, GIF, JPG or PNG. -- Regards, Laurent Pinchart ___ dri-devel mailing list dri-devel@lists.freedesktop.org
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi Maxime, On Wednesday 15 Feb 2017 13:38:44 Maxime Ripard wrote: > On Mon, Feb 13, 2017 at 11:20:51AM +, Daniel Stone wrote: > > On 13 February 2017 at 10:54, Maxime Ripard wrote: > >> On Sun, Feb 12, 2017 at 02:28:11PM +0200, Laurent Pinchart wrote: > >>> On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: > This patch add a config to support to create multi buffer for cma > fbdev. Such as double buffer and triple buffer. > > Cma fbdev is convient to add a legency fbdev. And still many Android > devices use fbdev now and at least double buffer is needed for these > Android devices, so that a buffer flip can be operated. It will need > some time for Android device vendors to abondon legency fbdev. So > multi buffer for fbdev is needed. > >>> > >>> How exactly do we expect Android to move away from fbdev if we add > >>> features to the fbdev compat layer ? I'd much rather make it clear to > >>> them that fbdev is a thing from the past and that they'd better > >>> migrate now. > >> > >> If your point is that merging this patch will slow down the Android > >> move away from fbdev, I disagree with that (obviously). > >> > >> I don't care at all about Android on my platform of choice, but don't > >> see how that merging this patch will change anything. > >> > >> Let's be honest, Android trees typically have thousands of patches on > >> top of mainline. Do you think a simple, 15 LoC, patch will make any > >> difference to vendors? If they want to stay on fbdev and have that > >> feature, they'll just merge this patch, done. > > > > So, in that case, why not just let them do that? They'd already have > > to add patches to use this, surely; we don't have anything in mainline > > kernels which allows people to actually use this larger allocation. > > Apart from software mmap() and using panning to do flips, but I'm > > taking it as a given that people shipping Android on their devices > > aren't using software rendering. > > My point was that you're not doing it more difficult for people not > willing to contribute upstream, you're just making it more difficult > for people who want to contribute. > > The whole argument to engage vendors upstream is that we sell them > that eventually they will be able to just use whatever kernel release > is on kernel.org or in their distro of choice. > > If those people depend on a feature that is entirely rejected > upstream, then they'll have to carry that patch in their tree, > creating a BSP in the process. And that reduces greatly the strength > of the "you should contribute" argument, making them less involved. No, they should not carry an out-of-tree patch, they should not use that feature in the first place. fbdev is a dead-end, Linux has clearly decided to move to DRM/KMS. Any vendor who wants to keep using fbdev is shooting themselves in the foot, as the more they depend on fbdev, the more painful it will be to switch later when they will have no choice. Switching sooner than later is the best decision, and I'd argue that by making it easier to stay on fbdev we would actually hurt those vendors in the longer term. > >> However, what I do see is that three different people/organisations > >> have now expressed interest in that feature, on three different > >> SoCs. If that patch needed a significant rework of the fbdev layer, > >> then yes, I might agree that it's not worth it. But in this case, it's > >> pretty trivial. > >> > >> The only people you're "punishing" here with that kind of concern are > >> the people who actually play fair and want not to have any patches and > >> everything upstream. > > > > I would hazard a guess that most users of this have out-of-tree GPU > > drivers. > > Out of tree GPU drivers, that can be distributed separately from the > kernel, just like any out of tree module can. This doesn't require any > kernel patches at all. That might be true in some cases, but usually those GPU drivers require heavy patching of at least the display controller driver. -- Regards, Laurent Pinchart ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi, On Thu, Feb 16, 2017 at 01:28:24PM +0100, Tobias Jakobi wrote: > Hello, > > I'm not sure if I'm missing something here, but I don't see how this is > supposed to work. > > This just multiplies the height of the drm_mode_fb_cmd2 object with the > number of buffers. Let's say I have width=1024, height=768, then now I > have a framebuffer which has height=2304 (in the num_buffers=3 case). At > some point this FB is set as the primary plane, giving us a 1024x2304 > mode. I don't think that this is intended. > > In my opinion this multi-buffer thing should touch drm_mode_fb_cmd2 at > all. The underlying BO should be larger, but not the FB itself. If this > is supposed to work, then the fbdev helpers should create as many FBs as > there are buffers, and then offset each of these FB into the BO. This only increases the virtual resolution, not the visible one. > What I'm also not seeing is code that handles the fbdev's virtual > resolutions. After all num_buffers should only increase those. Same for > the panning ioctl(). This is already implemented through drm_fb_helper_pan_display. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com signature.asc Description: PGP signature ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hello, I'm not sure if I'm missing something here, but I don't see how this is supposed to work. This just multiplies the height of the drm_mode_fb_cmd2 object with the number of buffers. Let's say I have width=1024, height=768, then now I have a framebuffer which has height=2304 (in the num_buffers=3 case). At some point this FB is set as the primary plane, giving us a 1024x2304 mode. I don't think that this is intended. In my opinion this multi-buffer thing should touch drm_mode_fb_cmd2 at all. The underlying BO should be larger, but not the FB itself. If this is supposed to work, then the fbdev helpers should create as many FBs as there are buffers, and then offset each of these FB into the BO. What I'm also not seeing is code that handles the fbdev's virtual resolutions. After all num_buffers should only increase those. Same for the panning ioctl(). So, is this just a part of a larger series? I remember seeing such a hack in the Hardkernel vendor kernel. But there it only worked because of some bug in the crtc (mixer) code. With best wishes, Tobias P.S.: I'm signed up to dri-devel in digest mode, so sorry if this mail doesn't properly show up in the corresponding ml thread. ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi, On Tue, Feb 14, 2017 at 11:25:08PM +0200, Laurent Pinchart wrote: > Hi Daniel, > > On Tuesday 14 Feb 2017 21:09:51 Daniel Vetter wrote: > > On Mon, Feb 13, 2017 at 11:20:51AM +, Daniel Stone wrote: > > > On 13 February 2017 at 10:54, Maxime Ripard wrote: > > >> On Sun, Feb 12, 2017 at 02:28:11PM +0200, Laurent Pinchart wrote: > > >>> On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: > > This patch add a config to support to create multi buffer for cma > > fbdev. Such as double buffer and triple buffer. > > > > Cma fbdev is convient to add a legency fbdev. And still many Android > > devices use fbdev now and at least double buffer is needed for these > > Android devices, so that a buffer flip can be operated. It will need > > some time for Android device vendors to abondon legency fbdev. So > > multi buffer for fbdev is needed. > > >>> > > >>> How exactly do we expect Android to move away from fbdev if we add > > >>> features to the fbdev compat layer ? I'd much rather make it clear to > > >>> them that fbdev is a thing from the past and that they'd better > > >>> migrate now. > > >> > > >> If your point is that merging this patch will slow down the Android > > >> move away from fbdev, I disagree with that (obviously). > > >> > > >> I don't care at all about Android on my platform of choice, but don't > > >> see how that merging this patch will change anything. > > >> > > >> Let's be honest, Android trees typically have thousands of patches on > > >> top of mainline. Do you think a simple, 15 LoC, patch will make any > > >> difference to vendors? If they want to stay on fbdev and have that > > >> feature, they'll just merge this patch, done. > > > > > > So, in that case, why not just let them do that? They'd already have > > > to add patches to use this, surely; we don't have anything in mainline > > > kernels which allows people to actually use this larger allocation. > > > Apart from software mmap() and using panning to do flips, but I'm > > > taking it as a given that people shipping Android on their devices > > > aren't using software rendering. > > > > I think we need to make a distinction between fbdev the subsystem in the > > kernel, and fbdev the uabi: > > > > - fbdev the subsystem is completely dead in upstream. I think we have full > > agreement on that. > > - fbdev the uabi isn't, and if we can get more users from fbdev based > > drivers to kms/atomic drivers by adding fairly simple stuff like this, > > I'm all for it. > > The real question, in my opinion, is how to get more users for the DRM/KMS > userspace API, to help killing the fbdev API. What's the incentive for > userspace to migrate if we tell them that we're going to support the fbdev > API > forever, and will even go through the trouble of extending the supported > feature set ? I have a customer who wouldn't have migrated their userspace to > DRM/KMS if these two patches had been merged a few years ago. If those patches are not in, then I can see three ways to support old / deficient userspaces: 1) Carry those patches out of tree 2) Write an fbdev driver for the display engine 3) Rewrite the userspace components While 3. would arguably be the best option, this isn't always one, unfortunately. And as a community, I think 1 and 2 are not very good for us. 1. will drive away vendors from our community, undermining the effort we've been doing for a few years. And 2 will result in a driver we really don't want to merge (so useless), and even if it would out of tree, that would make it one less system / board / SoC *with* DRM/KMS APIs, reducing the interest of switching for application developpers. If we really want to make people switch to DRM / KMS, we have to make it ubiquitous. And if we want to make it ubiquitous, we really want to have a transition period where people will have both APIs, supported in a decent enough way. And then, that's a win for everyone, because in the process you get fbdev (booo!) and KMS (yay!), allowing for people to switch over, and eventually kill the emulation entirely. But it's far too early for that. I mean, we don't even have an fbv replacement yet... Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com signature.asc Description: PGP signature ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi, On Mon, Feb 13, 2017 at 11:20:51AM +, Daniel Stone wrote: > Hi Maxime, > > On 13 February 2017 at 10:54, Maxime Ripard > wrote: > > On Sun, Feb 12, 2017 at 02:28:11PM +0200, Laurent Pinchart wrote: > >> On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: > >> > This patch add a config to support to create multi buffer for cma fbdev. > >> > Such as double buffer and triple buffer. > >> > > >> > Cma fbdev is convient to add a legency fbdev. And still many Android > >> > devices use fbdev now and at least double buffer is needed for these > >> > Android devices, so that a buffer flip can be operated. It will need > >> > some time for Android device vendors to abondon legency fbdev. So multi > >> > buffer for fbdev is needed. > >> > >> How exactly do we expect Android to move away from fbdev if we add > >> features to > >> the fbdev compat layer ? I'd much rather make it clear to them that fbdev > >> is a > >> thing from the past and that they'd better migrate now. > > > > If your point is that merging this patch will slow down the Android > > move away from fbdev, I disagree with that (obviously). > > > > I don't care at all about Android on my platform of choice, but don't > > see how that merging this patch will change anything. > > > > Let's be honest, Android trees typically have thousands of patches on > > top of mainline. Do you think a simple, 15 LoC, patch will make any > > difference to vendors? If they want to stay on fbdev and have that > > feature, they'll just merge this patch, done. > > So, in that case, why not just let them do that? They'd already have > to add patches to use this, surely; we don't have anything in mainline > kernels which allows people to actually use this larger allocation. > Apart from software mmap() and using panning to do flips, but I'm > taking it as a given that people shipping Android on their devices > aren't using software rendering. My point was that you're not doing it more difficult for people not willing to contribute upstream, you're just making it more difficult for people who want to contribute. The whole argument to engage vendors upstream is that we sell them that eventually they will be able to just use whatever kernel release is on kernel.org or in their distro of choice. If those people depend on a feature that is entirely rejected upstream, then they'll have to carry that patch in their tree, creating a BSP in the process. And that reduces greatly the strength of the "you should contribute" argument, making them less involved. > > However, what I do see is that three different people/organisations > > have now expressed interest in that feature, on three different > > SoCs. If that patch needed a significant rework of the fbdev layer, > > then yes, I might agree that it's not worth it. But in this case, it's > > pretty trivial. > > > > The only people you're "punishing" here with that kind of concern are > > the people who actually play fair and want not to have any patches and > > everything upstream. > > I would hazard a guess that most users of this have out-of-tree GPU > drivers. Out of tree GPU drivers, that can be distributed separately from the kernel, just like any out of tree module can. This doesn't require any kernel patches at all. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com signature.asc Description: PGP signature ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi Daniel, On Tuesday 14 Feb 2017 21:09:51 Daniel Vetter wrote: > On Mon, Feb 13, 2017 at 11:20:51AM +, Daniel Stone wrote: > > On 13 February 2017 at 10:54, Maxime Ripard wrote: > >> On Sun, Feb 12, 2017 at 02:28:11PM +0200, Laurent Pinchart wrote: > >>> On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: > This patch add a config to support to create multi buffer for cma > fbdev. Such as double buffer and triple buffer. > > Cma fbdev is convient to add a legency fbdev. And still many Android > devices use fbdev now and at least double buffer is needed for these > Android devices, so that a buffer flip can be operated. It will need > some time for Android device vendors to abondon legency fbdev. So > multi buffer for fbdev is needed. > >>> > >>> How exactly do we expect Android to move away from fbdev if we add > >>> features to the fbdev compat layer ? I'd much rather make it clear to > >>> them that fbdev is a thing from the past and that they'd better > >>> migrate now. > >> > >> If your point is that merging this patch will slow down the Android > >> move away from fbdev, I disagree with that (obviously). > >> > >> I don't care at all about Android on my platform of choice, but don't > >> see how that merging this patch will change anything. > >> > >> Let's be honest, Android trees typically have thousands of patches on > >> top of mainline. Do you think a simple, 15 LoC, patch will make any > >> difference to vendors? If they want to stay on fbdev and have that > >> feature, they'll just merge this patch, done. > > > > So, in that case, why not just let them do that? They'd already have > > to add patches to use this, surely; we don't have anything in mainline > > kernels which allows people to actually use this larger allocation. > > Apart from software mmap() and using panning to do flips, but I'm > > taking it as a given that people shipping Android on their devices > > aren't using software rendering. > > I think we need to make a distinction between fbdev the subsystem in the > kernel, and fbdev the uabi: > > - fbdev the subsystem is completely dead in upstream. I think we have full > agreement on that. > - fbdev the uabi isn't, and if we can get more users from fbdev based > drivers to kms/atomic drivers by adding fairly simple stuff like this, > I'm all for it. The real question, in my opinion, is how to get more users for the DRM/KMS userspace API, to help killing the fbdev API. What's the incentive for userspace to migrate if we tell them that we're going to support the fbdev API forever, and will even go through the trouble of extending the supported feature set ? I have a customer who wouldn't have migrated their userspace to DRM/KMS if these two patches had been merged a few years ago. I'd rather *reduce* the supported feature set over time until we can finally switch fbdev off. > Which means: Yes, I fully plan to merge this, it makes sense. It even > _helps_ by making fbdev-the-subsystem even deader. Making live hard for > out-of-tree folks or folks with shit userspace doesn't make sense, at > least if the only benefit for us is that we'll feel pure about our > intentions :-) -- Regards, Laurent Pinchart ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
On Mon, Feb 13, 2017 at 11:20:51AM +, Daniel Stone wrote: > Hi Maxime, > > On 13 February 2017 at 10:54, Maxime Ripard > wrote: > > On Sun, Feb 12, 2017 at 02:28:11PM +0200, Laurent Pinchart wrote: > >> On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: > >> > This patch add a config to support to create multi buffer for cma fbdev. > >> > Such as double buffer and triple buffer. > >> > > >> > Cma fbdev is convient to add a legency fbdev. And still many Android > >> > devices use fbdev now and at least double buffer is needed for these > >> > Android devices, so that a buffer flip can be operated. It will need > >> > some time for Android device vendors to abondon legency fbdev. So multi > >> > buffer for fbdev is needed. > >> > >> How exactly do we expect Android to move away from fbdev if we add > >> features to > >> the fbdev compat layer ? I'd much rather make it clear to them that fbdev > >> is a > >> thing from the past and that they'd better migrate now. > > > > If your point is that merging this patch will slow down the Android > > move away from fbdev, I disagree with that (obviously). > > > > I don't care at all about Android on my platform of choice, but don't > > see how that merging this patch will change anything. > > > > Let's be honest, Android trees typically have thousands of patches on > > top of mainline. Do you think a simple, 15 LoC, patch will make any > > difference to vendors? If they want to stay on fbdev and have that > > feature, they'll just merge this patch, done. > > So, in that case, why not just let them do that? They'd already have > to add patches to use this, surely; we don't have anything in mainline > kernels which allows people to actually use this larger allocation. > Apart from software mmap() and using panning to do flips, but I'm > taking it as a given that people shipping Android on their devices > aren't using software rendering. I think we need to make a distinction between fbdev the subsystem in the kernel, and fbdev the uabi: - fbdev the subsystem is completely dead in upstream. I think we have full agreement on that. - fbdev the uabi isn't, and if we can get more users from fbdev based drivers to kms/atomic drivers by adding fairly simple stuff like this, I'm all for it. Which means: Yes, I fully plan to merge this, it makes sense. It even _helps_ by making fbdev-the-subsystem even deader. Making live hard for out-of-tree folks or folks with shit userspace doesn't make sense, at least if the only benefit for us is that we'll feel pure about our intentions :-) Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi Maxime, On 13 February 2017 at 10:54, Maxime Ripard wrote: > On Sun, Feb 12, 2017 at 02:28:11PM +0200, Laurent Pinchart wrote: >> On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: >> > This patch add a config to support to create multi buffer for cma fbdev. >> > Such as double buffer and triple buffer. >> > >> > Cma fbdev is convient to add a legency fbdev. And still many Android >> > devices use fbdev now and at least double buffer is needed for these >> > Android devices, so that a buffer flip can be operated. It will need >> > some time for Android device vendors to abondon legency fbdev. So multi >> > buffer for fbdev is needed. >> >> How exactly do we expect Android to move away from fbdev if we add features >> to >> the fbdev compat layer ? I'd much rather make it clear to them that fbdev is >> a >> thing from the past and that they'd better migrate now. > > If your point is that merging this patch will slow down the Android > move away from fbdev, I disagree with that (obviously). > > I don't care at all about Android on my platform of choice, but don't > see how that merging this patch will change anything. > > Let's be honest, Android trees typically have thousands of patches on > top of mainline. Do you think a simple, 15 LoC, patch will make any > difference to vendors? If they want to stay on fbdev and have that > feature, they'll just merge this patch, done. So, in that case, why not just let them do that? They'd already have to add patches to use this, surely; we don't have anything in mainline kernels which allows people to actually use this larger allocation. Apart from software mmap() and using panning to do flips, but I'm taking it as a given that people shipping Android on their devices aren't using software rendering. > However, what I do see is that three different people/organisations > have now expressed interest in that feature, on three different > SoCs. If that patch needed a significant rework of the fbdev layer, > then yes, I might agree that it's not worth it. But in this case, it's > pretty trivial. > > The only people you're "punishing" here with that kind of concern are > the people who actually play fair and want not to have any patches and > everything upstream. I would hazard a guess that most users of this have out-of-tree GPU drivers. > I guess a much better strategy would be to provide an incentive to > moving to KMS. And I truely think there's one already, so it's just a > matter of time before people switch over. Fbdev emulation or not. The concern makes sense, but on the other hand, fbdev is deprecated: no new drivers, and no new features. Cheers, Daniel ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi Laurent, On Sun, Feb 12, 2017 at 02:28:11PM +0200, Laurent Pinchart wrote: > Hi Maxime, > > Thank you for the patch. > > On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: > > From: Xinliang Liu > > > > This patch add a config to support to create multi buffer for cma fbdev. > > Such as double buffer and triple buffer. > > > > Cma fbdev is convient to add a legency fbdev. And still many Android > > devices use fbdev now and at least double buffer is needed for these > > Android devices, so that a buffer flip can be operated. It will need > > some time for Android device vendors to abondon legency fbdev. So multi > > buffer for fbdev is needed. > > How exactly do we expect Android to move away from fbdev if we add features > to > the fbdev compat layer ? I'd much rather make it clear to them that fbdev is > a > thing from the past and that they'd better migrate now. If your point is that merging this patch will slow down the Android move away from fbdev, I disagree with that (obviously). I don't care at all about Android on my platform of choice, but don't see how that merging this patch will change anything. Let's be honest, Android trees typically have thousands of patches on top of mainline. Do you think a simple, 15 LoC, patch will make any difference to vendors? If they want to stay on fbdev and have that feature, they'll just merge this patch, done. However, what I do see is that three different people/organisations have now expressed interest in that feature, on three different SoCs. If that patch needed a significant rework of the fbdev layer, then yes, I might agree that it's not worth it. But in this case, it's pretty trivial. The only people you're "punishing" here with that kind of concern are the people who actually play fair and want not to have any patches and everything upstream. I guess a much better strategy would be to provide an incentive to moving to KMS. And I truely think there's one already, so it's just a matter of time before people switch over. Fbdev emulation or not. Ma -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com signature.asc Description: PGP signature ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi Maxime, Thank you for the patch. On Thursday 02 Feb 2017 11:31:56 Maxime Ripard wrote: > From: Xinliang Liu > > This patch add a config to support to create multi buffer for cma fbdev. > Such as double buffer and triple buffer. > > Cma fbdev is convient to add a legency fbdev. And still many Android > devices use fbdev now and at least double buffer is needed for these > Android devices, so that a buffer flip can be operated. It will need > some time for Android device vendors to abondon legency fbdev. So multi > buffer for fbdev is needed. How exactly do we expect Android to move away from fbdev if we add features to the fbdev compat layer ? I'd much rather make it clear to them that fbdev is a thing from the past and that they'd better migrate now. > Signed-off-by: Xinliang Liu > [s.chr...@phytec.de: Picking patch from > https://lkml.org/lkml/2015/9/14/188] > Signed-off-by: Stefan Christ > Signed-off-by: Maxime Ripard > --- > drivers/gpu/drm/Kconfig | 8 > drivers/gpu/drm/drm_fb_cma_helper.c | 8 +++- > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig > index ebfe8404c25f..2ca9bb26a4e4 100644 > --- a/drivers/gpu/drm/Kconfig > +++ b/drivers/gpu/drm/Kconfig > @@ -121,6 +121,14 @@ config DRM_KMS_CMA_HELPER > help > Choose this if you need the KMS CMA helper functions > > +config DRM_CMA_FBDEV_BUFFER_NUM > + int "Cma Fbdev Buffer Number" > + depends on DRM_KMS_CMA_HELPER > + default 1 > + help > + Defines the buffer number of cma fbdev. Default is one buffer. > + For double buffer please set to 2 and 3 for triple buffer. > + > source "drivers/gpu/drm/i2c/Kconfig" > > source "drivers/gpu/drm/arm/Kconfig" > diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c > b/drivers/gpu/drm/drm_fb_cma_helper.c index 81b3558302b5..e3f8b9e720a0 > 100644 > --- a/drivers/gpu/drm/drm_fb_cma_helper.c > +++ b/drivers/gpu/drm/drm_fb_cma_helper.c > @@ -411,6 +411,12 @@ static void drm_fbdev_cma_defio_fini(struct fb_info > *fbi) kfree(fbi->fbops); > } > > +static int fbdev_num_buffers = CONFIG_DRM_CMA_FBDEV_BUFFER_NUM; > +module_param(fbdev_num_buffers, int, 0444); > +MODULE_PARM_DESC(fbdev_num_buffers, > + "Number of frame buffers to allocate [default=" > + __MODULE_STRING(CONFIG_DRM_CMA_FBDEV_BUFFER_NUM) "]"); > + > /* > * For use in a (struct drm_fb_helper_funcs *)->fb_probe callback function > that * needs custom struct drm_framebuffer_funcs, like dirty() for > deferred_io use. @@ -437,7 +443,7 @@ int > drm_fbdev_cma_create_with_funcs(struct drm_fb_helper *helper, > bytes_per_pixel = DIV_ROUND_UP(sizes->surface_bpp, 8); > > mode_cmd.width = sizes->surface_width; > - mode_cmd.height = sizes->surface_height; > + mode_cmd.height = sizes->surface_height * fbdev_num_buffers; > mode_cmd.pitches[0] = sizes->surface_width * bytes_per_pixel; > mode_cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp, > sizes->surface_depth); -- Regards, Laurent Pinchart ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
Hi Daniel, On Thu, Feb 09, 2017 at 06:04:38PM +0100, Daniel Vetter wrote: > On Thu, Feb 02, 2017 at 11:31:56AM +0100, Maxime Ripard wrote: > > From: Xinliang Liu > > > > This patch add a config to support to create multi buffer for cma fbdev. > > Such as double buffer and triple buffer. > > > > Cma fbdev is convient to add a legency fbdev. And still many Android > > devices use fbdev now and at least double buffer is needed for these > > Android devices, so that a buffer flip can be operated. It will need > > some time for Android device vendors to abondon legency fbdev. So multi > > buffer for fbdev is needed. > > > > Signed-off-by: Xinliang Liu > > [s.chr...@phytec.de: Picking patch from > > https://lkml.org/lkml/2015/9/14/188] > > Signed-off-by: Stefan Christ > > Signed-off-by: Maxime Ripard > > --- > > drivers/gpu/drm/Kconfig | 8 > > drivers/gpu/drm/drm_fb_cma_helper.c | 8 +++- > > 2 files changed, 15 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig > > index ebfe8404c25f..2ca9bb26a4e4 100644 > > --- a/drivers/gpu/drm/Kconfig > > +++ b/drivers/gpu/drm/Kconfig > > @@ -121,6 +121,14 @@ config DRM_KMS_CMA_HELPER > > help > > Choose this if you need the KMS CMA helper functions > > > > +config DRM_CMA_FBDEV_BUFFER_NUM > > + int "Cma Fbdev Buffer Number" > > + depends on DRM_KMS_CMA_HELPER > > + default 1 > > + help > > + Defines the buffer number of cma fbdev. Default is one buffer. > > + For double buffer please set to 2 and 3 for triple buffer. > > + > > source "drivers/gpu/drm/i2c/Kconfig" > > > > source "drivers/gpu/drm/arm/Kconfig" > > diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c > > b/drivers/gpu/drm/drm_fb_cma_helper.c > > index 81b3558302b5..e3f8b9e720a0 100644 > > --- a/drivers/gpu/drm/drm_fb_cma_helper.c > > +++ b/drivers/gpu/drm/drm_fb_cma_helper.c > > @@ -411,6 +411,12 @@ static void drm_fbdev_cma_defio_fini(struct fb_info > > *fbi) > > kfree(fbi->fbops); > > } > > > > +static int fbdev_num_buffers = CONFIG_DRM_CMA_FBDEV_BUFFER_NUM; > > +module_param(fbdev_num_buffers, int, 0444); > > +MODULE_PARM_DESC(fbdev_num_buffers, > > +"Number of frame buffers to allocate [default=" > > +__MODULE_STRING(CONFIG_DRM_CMA_FBDEV_BUFFER_NUM) "]"); > > Pure bikshed: Should this be an overallocation %? 200 for > double-buffering, 100 as the default? I'm not against it, but would it make sense to allocate something like 120% of a buffer? > Slightly less bikesheddy: Can't we do this in the core helpers somehow? I guess that would move it to drm_fb_helper_single_fb_probe then? It makes sense. > I'd be nice if this is not cma specific. If it's not possible, I'd at > least move the symbol to drm_fb_helper.c, and add some kernel-doc around > it. That allows any other non-cma driver to at least implement support for > this. That also has the benefit of featuring it more prominently, in our > docs. I'll move it and add the kerneldoc. Thanks! Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com signature.asc Description: PGP signature ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH v2 1/2] drm/cma-helper: Add multi buffer support for cma fbdev
On Thu, Feb 02, 2017 at 11:31:56AM +0100, Maxime Ripard wrote: > From: Xinliang Liu > > This patch add a config to support to create multi buffer for cma fbdev. > Such as double buffer and triple buffer. > > Cma fbdev is convient to add a legency fbdev. And still many Android > devices use fbdev now and at least double buffer is needed for these > Android devices, so that a buffer flip can be operated. It will need > some time for Android device vendors to abondon legency fbdev. So multi > buffer for fbdev is needed. > > Signed-off-by: Xinliang Liu > [s.chr...@phytec.de: Picking patch from > https://lkml.org/lkml/2015/9/14/188] > Signed-off-by: Stefan Christ > Signed-off-by: Maxime Ripard > --- > drivers/gpu/drm/Kconfig | 8 > drivers/gpu/drm/drm_fb_cma_helper.c | 8 +++- > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig > index ebfe8404c25f..2ca9bb26a4e4 100644 > --- a/drivers/gpu/drm/Kconfig > +++ b/drivers/gpu/drm/Kconfig > @@ -121,6 +121,14 @@ config DRM_KMS_CMA_HELPER > help > Choose this if you need the KMS CMA helper functions > > +config DRM_CMA_FBDEV_BUFFER_NUM > + int "Cma Fbdev Buffer Number" > + depends on DRM_KMS_CMA_HELPER > + default 1 > + help > + Defines the buffer number of cma fbdev. Default is one buffer. > + For double buffer please set to 2 and 3 for triple buffer. > + > source "drivers/gpu/drm/i2c/Kconfig" > > source "drivers/gpu/drm/arm/Kconfig" > diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c > b/drivers/gpu/drm/drm_fb_cma_helper.c > index 81b3558302b5..e3f8b9e720a0 100644 > --- a/drivers/gpu/drm/drm_fb_cma_helper.c > +++ b/drivers/gpu/drm/drm_fb_cma_helper.c > @@ -411,6 +411,12 @@ static void drm_fbdev_cma_defio_fini(struct fb_info *fbi) > kfree(fbi->fbops); > } > > +static int fbdev_num_buffers = CONFIG_DRM_CMA_FBDEV_BUFFER_NUM; > +module_param(fbdev_num_buffers, int, 0444); > +MODULE_PARM_DESC(fbdev_num_buffers, > + "Number of frame buffers to allocate [default=" > + __MODULE_STRING(CONFIG_DRM_CMA_FBDEV_BUFFER_NUM) "]"); Pure bikshed: Should this be an overallocation %? 200 for double-buffering, 100 as the default? Slightly less bikesheddy: Can't we do this in the core helpers somehow? I'd be nice if this is not cma specific. If it's not possible, I'd at least move the symbol to drm_fb_helper.c, and add some kernel-doc around it. That allows any other non-cma driver to at least implement support for this. That also has the benefit of featuring it more prominently, in our docs. Besides these bikesheds/question, looks all reasonable to me. If you can get some more acks would be great, but will merge anyway. -Daniel > + > /* > * For use in a (struct drm_fb_helper_funcs *)->fb_probe callback function > that > * needs custom struct drm_framebuffer_funcs, like dirty() for deferred_io > use. > @@ -437,7 +443,7 @@ int drm_fbdev_cma_create_with_funcs(struct drm_fb_helper > *helper, > bytes_per_pixel = DIV_ROUND_UP(sizes->surface_bpp, 8); > > mode_cmd.width = sizes->surface_width; > - mode_cmd.height = sizes->surface_height; > + mode_cmd.height = sizes->surface_height * fbdev_num_buffers; > mode_cmd.pitches[0] = sizes->surface_width * bytes_per_pixel; > mode_cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp, > sizes->surface_depth); > -- > git-series 0.8.11 > ___ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
