On Mon, Jul 1, 2019 at 11:24 PM Robin Murphy <robin.murphy@xxxxxxx> wrote: > > On 01/07/2019 18:47, Pankaj Suryawanshi wrote: > >> If you want a kernel mapping, *don't* explicitly request not to have a > >> kernel mapping in the first place. It's that simple. > >> > > > > Do you mean do not use dma-api ? because if i used dma-api it will give you > > mapped virtual address. > > or i have to use directly cma_alloc() in my driver. // if i used this > > approach i need to reserved more vmalloc area. > > No, I mean just call dma_alloc_attrs() normally *without* adding the > DMA_ATTR_NO_KERNEL_MAPPING flag. That flag means "I never ever want to > make CPU accesses to this buffer from the kernel" - that is clearly not > the case for your code, so it is utterly nonsensical to still pass the > flag but try to hack around it later. Actually my use case is that i want virtual mapping only when i will play video as my vpu/gpu driver is design like that. and i am using 32-bit so virtual memory is splitted as 3G/1G so dont have enough memory for all the time to mapped with kernel space. Lets say i am allocating 400MB for driver but i want only 30MB for virtual mapping (not everytime) that is the case. > > > Robin.
