On Thu, 2016-01-21 at 16:58 -0800, Laura Abbott wrote: > On 01/21/2016 12:19 PM, Jon Medhurst (Tixy) wrote: [...] > > If sg_dma_len() is correct or acceptable then it seems to me that the > > ION code should set that length. Especially as the comment in the code > > implies it's faking a call to map_sg and grepping the kernel tree for > > real implementations of that functionality seems to show the dma_address > > getting set. > > > > As you can probably tell, I feel I may be on shaky ground. This is > > because I don't fully understanding the code and suspecting both the ION > > and GPU code is rather dodgy (and possibly the bits in between :-) > > > > I blame the Ion code completely. I remember hitting a similar problem > with other out of tree drivers. The solution then was to have drivers > switch to using sg->length instead of sg_dma_len given the state of that > tree. For the Mali driver, if it is ever going to be backed by an IOMMU > you will need to use sg_dma_len so I think at least that part of your > code is correct. > > Thinking about it some, I'm okay with the patch going in. I thought > there was some reason why the out of tree code from before didn't just > do this hack but I can't remember it. It may have been an out of tree > use case. This does go well with Ion's behavior of pretending to do > DMA mapping. More out of tree users can plead their case if it breaks. Well, the $subject patch is copying the value of 'length' into 'dma_length', and if dma_length was previously uninitialised then I don't see that it can really cause additional problems for ION users. (I hate the way I've been using 'if' a lot so I'm going to spend some time educating myself.) > Acked-by: Laura Abbott <labbott@xxxxxxxxxx> Thanks -- Tixy _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
