On Tue, 22 Jan 2019 21:25:35 +0100, Mark Brown wrote: > > On Mon, Jan 21, 2019 at 03:15:43PM +0100, Jaroslav Kysela wrote: > > Dne 21.1.2019 v 13:40 Mark Brown napsal(a): > > > > It was the bit about adding more extended permission control that I was > > > worried about there, not the initial O_APPEND bit. Indeed the O_APPEND > > > bit sounds like it might also work from the base buffer sharing point of > > > view, I have to confess I'd not heard of that feature before (it didn't > > > come up in the discussion when Eric raised this in Prague). > > > With permissions, I meant to make possible to restrict the file > > descriptor operations (ioctls) for the depending task (like access to > > the DMA buffer, synchronize it for the non-coherent platforms and maybe > > read/write the actual position, delay etc.). It should be relatively > > easy to implement using the snd_pcm_file structure. > > Right, that's what I understood you to mean. If you want to have a > policy saying "it's OK to export a PCM file descriptor if it's only got > permissions X and Y" the security module is going to need to know about > the mechanism for setting those permissions. With dma_buf that's all a > bit easier as there's less new stuff, though I've no real idea how much > of a big deal that actually is. There are many ways to implement such a thing, yeah. If we'd need an implementation that is done solely in the sound driver layer, I can imagine to introduce either a new ioctl or an open flag (like O_EXCL) to specify the restricted sharing. That is, a kind of master / slave model where only the master is allowed to manipulate the stream while the slave can mmap, read/write and get status. thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
