On 03/14/2017 07:47 AM, Benjamin Gaignard wrote:
2017-03-13 22:09 GMT+01:00 Laura Abbott labbott@redhat.com:
On 03/12/2017 12:05 PM, Daniel Vetter wrote:
On Sun, Mar 12, 2017 at 2:34 PM, Benjamin Gaignard benjamin.gaignard@linaro.org wrote:
2017-03-09 18:38 GMT+01:00 Laura Abbott labbott@redhat.com:
On 03/09/2017 02:00 AM, Benjamin Gaignard wrote:
2017-03-06 17:04 GMT+01:00 Daniel Vetter daniel@ffwll.ch: > On Mon, Mar 06, 2017 at 11:58:05AM +0100, Mark Brown wrote: >> On Mon, Mar 06, 2017 at 11:40:41AM +0100, Daniel Vetter wrote: >> >>> No one gave a thing about android in upstream, so Greg KH just dumped it >>> all into staging/android/. We've discussed ION a bunch of times, recorded >>> anything we'd like to fix in staging/android/TODO, and Laura's patch >>> series here addresses a big chunk of that. >> >>> This is pretty much the same approach we (gpu folks) used to de-stage the >>> syncpt stuff. >> >> Well, there's also the fact that quite a few people have issues with the >> design (like Laurent). It seems like a lot of them have either got more >> comfortable with it over time, or at least not managed to come up with >> any better ideas in the meantime. > > See the TODO, it has everything a really big group (look at the patch for > the full Cc: list) figured needs to be improved at LPC 2015. We don't just > merge stuff because merging stuff is fun :-) > > Laurent was even in that group ... > -Daniel
For me those patches are going in the right direction.
I still have few questions:
- since alignment management has been remove from ion-core, should it
be also removed from ioctl structure ?
Yes, I think I'm going to go with the suggestion to fixup the ABI so we don't need the compat layer and as part of that I'm also dropping the align argument.
- can you we ride off ion_handle (at least in userland) and only
export a dma-buf descriptor ?
Yes, I think this is the right direction given we're breaking everything anyway. I was debating trying to keep the two but moving to only dma bufs is probably cleaner. The only reason I could see for keeping the handles is running out of file descriptors for dma-bufs but that seems unlikely.
In the future how can we add new heaps ? Some platforms have very specific memory allocation requirements (just have a look in the number of gem custom allocator in drm) Do you plan to add heap type/mask for each ?
Yes, that was my thinking.
My concern is about the policy to adding heaps, will you accept "customs" heap per platforms ? per devices ? or only generic ones ? If you are too strict, we will have lot of out-of-tree heaps and if you accept of of them it will be a nightmare to maintain....
I think ion should expose any heap that's also directly accessible to devices using dma_alloc(_coherent). That should leave very few things left, like your SMA heap.
Another point is how can we put secure rules (like selinux policy) on heaps since all the allocations go to the same device (/dev/ion) ? For example, until now, in Android we have to give the same access rights to all the process that use ION. It will become problem when we will add secure heaps because we won't be able to distinguish secure processes to standard ones or set specific policy per heaps. Maybe I'm wrong here but I have never see selinux policy checking an ioctl field but if that exist it could be a solution.
Hm, we might want to expose all the heaps as individual /dev/ion_$heapname nodes? Should we do this from the start, since we're massively revamping the uapi anyway (imo not needed, current state seems to work too)? -Daniel
I thought about that. One advantage with separate /dev/ion_$heap
Should we use /devi/ion/$heap instead of /dev/ion_$heap ? I think it would be easier for user to look into one directory rather then in whole /dev to find the heaps
If we decide to move away from /dev/ion we can consider it.
is that we don't have to worry about a limit of 32 possible heaps per system (32-bit heap id allocation field). But dealing with an ioctl seems easier than names. Userspace might be less likely to hardcode random id numbers vs. names as well.
In the futur I think that heap type will be replaced by a "get caps" ioctl which will describe heap capabilities. At least that is my understanding of kernel part of "unix memory allocator" project
I don't think it will be completely replaced. A heap can have multiple capabilities so I suspect there will need to be some cap -> allocation instance translation. Of course all this is wild speculation since much of the unix memory allocator isn't well defined yet.
Thanks, Laura