On 07/07/2020 15:33, Dave Stevenson wrote: > Hi Hans, Sergey, & the list. > > I'm running the latest v4l2-compliance (85ec2917 "v4l2-compliance: fix > stateful encoder tests") against the Raspberry Pi vendor 5.4 kernel > tree. That means the kernel isn't supporting > V4L2_BUF_FLAG_NO_CACHE_[INVALIDATE|CLEAN] flags on the buffers, nor is > anything advertising V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS. I'm > getting failures in setupMmap. > > With patch "784be6a v4l2-utils: test cache_hints for MMAP queues" the > test deliberately sets V4L2_BUF_FLAG_NO_CACHE_INVALIDATE and > V4L2_BUF_FLAG_NO_CACHE_CLEAN on the buffers that it queues. > Nothing in the kernel is expecting to manipulate those flags as the > behaviour wasn't really defined before, but the test is failed if they > aren't cleared. The v4l2 core would only clear them if the kernel > includes the patch "f5f5fa7 media: videobuf2: handle V4L2 buffer cache > flags", which currently means only linuxtv/master as that patch isn't > even in 5.8-rc3. > > Is it really valid to look at the V4L2_BUF_FLAG_NO_CACHE_* flags at > all if V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS isn't set? If the > capability isn't advertised, surely the state of those bits is > undefined. v4l2-compliance tests are in sync with our master and it expects that that kernel is used. It is possible in rare cases to add a version check (use the version field returned by QUERYCAP) to determine if a feature is in the latest kernel. It's not done anywhere in the current compliance test, but I'd accept a patch that disables this test for kernels < 5.9 (since this feature will land in 5.9). Regards, Hans
