On Mon, Jun 3, 2019 at 2:25 PM Pierre Yves MORDRET <pierre-yves.mordret@xxxxxx> wrote: > > Hi all, > > Many thanks for your valuable support and answers. > > Since Dumb mmap is for buffer created using dumb_create ioctl we won't use it > anymore. In place a mmap/ummap is called with DMA Buf FD. > After some tests it seems working in our side. Please note that with dma-buf you need to call the begin/end cpu access ioctl, or depending upon driver/platform the mmap access might be incoherent. -Daniel > > Many thanks again. > Regards. > > On 5/31/19 1:36 PM, Daniel Vetter wrote: > > On Fri, May 31, 2019 at 1:28 PM Noralf Trønnes <noralf@xxxxxxxxxxx> wrote: > >> > >> Hi, > >> > >> [add Daniel Vetter] > >> [cc dri-devel] > >> > >> Den 29.05.2019 15.09, skrev Pierre Yves MORDRET: > >>> Hello Noralf, > >>> > >>> Sorry for bothering you with question but I need to better understand the > >>> rational about a patch you did in DRM/GEM. > >>> > >>> First of all, let me introduce myself. > >>> I'm currently employee to STMicroelectronics company and in charge of GPU > >>> integration within STM32 MPU (Cortex A7 + Cortex M4) > >>> > >>> On Cortex A7 is running a Linux Kernel 4.19 as for today. > >>> > >>> We came across some trouble when we switch from Kernel 4.14 to 4.19 for GPU > >>> stack. On august you submit this commit : > >>> > >>> 90378e58919285637aa0f063c04ba0c6449d98b1 > >>> drm/gem: drm_gem_dumb_map_offset(): reject dma-buf > >>> > >>> Reject mapping an imported dma-buf since is's an invalid use-case. > >>> > >>> In Userland GPU stack we have such statements : > >>> bo_map_fd > >>> DRM_IOCTL_MODE_MAP_DUMB > >>> mmap (offset) > >>> > >>> With the patch above, ioctl returns an error EINVAL and prevents the nmap. > >>> As for today we revert this patch and it works fine in our end. > > > > Link to source code would be good. > > > >>> Thus the questions are : > >>> - what is the rational behind this fix ? > >>> - What we doing wrong this situation ? > >>> - What do we need in such situation ? > >>> > >> > >> I need to pass those on to Daniel Vetter (DRM maintainer) since he > >> wanted the change. The details were never clear to me. > >> Some of the discussion is here: > >> https://patchwork.freedesktop.org/patch/172242/ > > > > Dumb mmap is for buffer created using dumb_create ioctl, and nothing > > else. Anything else really has at best undefined behaviour. E.g. for > > dma-buf you really need to call the begin/end_cpu_access ioctl, and > > dumb buffers simply have no provision for that. Hence why we can't > > support this in general. > > > > Thanks, Daniel > > -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
