> -----Original Message----- > From: Russell King - ARM Linux [mailto:linux@xxxxxxxxxxxxxxxx] > Sent: Tuesday, June 18, 2013 5:43 PM > To: Inki Dae > Cc: 'Maarten Lankhorst'; 'linux-fbdev'; 'Kyungmin Park'; 'DRI mailing > list'; 'Rob Clark'; 'myungjoo.ham'; 'YoungJun Cho'; 'Daniel Vetter'; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx > Subject: Re: [RFC PATCH v2] dmabuf-sync: Introduce buffer synchronization > framework > > On Tue, Jun 18, 2013 at 02:27:40PM +0900, Inki Dae wrote: > > So I'd like to ask for other DRM maintainers. How do you think about it? > it > > seems like that Intel DRM (maintained by Daniel), OMAP DRM (maintained > by > > Rob) and GEM CMA helper also have same issue Russell pointed out. I > think > > not only the above approach but also the performance is very important. > > CMA uses coherent memory to back their buffers, though that might not be > true of memory obtained from other drivers via dma_buf. Plus, there is > no support in the CMA helper for exporting or importng these buffers. > It's not so. Please see Dave's drm next. recently dmabuf support for the CMA helper has been merged to there. > I guess Intel i915 is only used on x86, which is a coherent platform and > requires no cache maintanence for DMA. > > OMAP DRM does not support importing non-DRM buffers buffers back into Correct. TODO yet. > DRM. Moreover, it will suffer from the problems I described if any > attempt is made to write to the buffer after it has been re-imported. > > Lastly, I should point out that the dma_buf stuff is really only useful > when you need to export a dma buffer from one driver and import it into > another driver - for example to pass data from a camera device driver to Most people know that. > a display device driver. It shouldn't be used within a single driver > as a means of passing buffers between userspace and kernel space. What I try to do is not really such ugly thing. What I try to do is to notify that, when CPU tries to access a buffer , to kernel side through dmabuf interface. So it's not really to send the buffer to kernel. Thanks, Inki Dae -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
