On Thu, 8 Jul 2010 12:14:28 -0400, Kristian Høgsberg <krh@xxxxxxxxxxxxx> wrote: > On Thu, Jul 8, 2010 at 11:59 AM, Keith Packard <keithp@xxxxxxxxxx> wrote: > > On Thu,  8 Jul 2010 11:23:25 -0400, Kristian Høgsberg <krh@xxxxxxxxxxxxx> wrote: > > > >>  - a mechanism to attach a binary blob to an flink_to buffer name. > >>   open_with_data returns the data.  Userspace (typically libdrm) > >>   decides the layout and versioning of the blob and the contents > >>   will be chipset specific.  it's an opaque blob to the kernel, > >>   which doesn't need to know about stride and formats etc. > > > > Arbitrary binary blobs considered harmful? Even if the kernel doesn't > > need to know all of this data, having it in an explicit (versioned) > > format will protect applications from randomly mis-interpreting the data. > > I talked with ickle about that and whether or not to include a > version+format u32 for the data in the ioctl args. He convinced me > that the kernel didn't need to know about the layout of the blob and > that requiring by convention that the first u32 of the blob is the > version+format u32 would suffice. I can go either way on this, but I > guess I have a small preference for making it part of the ioctl args > as you suggest. I am not going to argue with someone who has been tackling the issue of protocol extensions for 25 years... ;-) My argument was based around that the current system is designed as a directory of opaque objects and so the extended attributes should be kept opaque to the kernel as well and left open to interpretation by userland. What I am most unclear about is under which circumstances is this backchannel communication preferable to passing the extra information over the IPC that needs to be performed anyway in order to open a surface. -ickle -- Chris Wilson, Intel Open Source Technology Centre
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