On Tue, Sep 02, 2025 at 03:37:45PM -0700, John Stultz wrote:
On Tue, Sep 2, 2025 at 8:46 AM Thierry Reding thierry.reding@gmail.com wrote:
From: Thierry Reding treding@nvidia.com
Add a callback to struct dma_heap_ops that heap providers can implement to show information about the state of the heap in debugfs. A top-level directory named "dma_heap" is created in debugfs and individual files will be named after the heaps.
I know its debugfs, but this feels a little loosey-goosey as an uAPI.
Well, the whole point of debugfs is that it's not really an ABI. Nothing should ever rely on the presence of these files.
Is there any expected format for the show function?
What would other dmabuf heaps ideally export via this interface?
I've thought about this a bit and I'm not sure it makes sense to standardize on this. I think on one hand having a list of buffers exported by the dma-buf heap is probably the lowest common denominator, but then there might be a bunch of other things that are very heap- specific that some heap might want to export.
Is there some consistent dma_heap-ish concept for it to justify it being under a dma_heap directory, and not just an independent debugfs file for the driver implementing the dmabuf heap?
Well, I think just the fact that it's a dma-heap would qualify its corresponding debugfs to be in a well-known location. We could of course pick some arbitrary location, but that's just a recipe for chaos because then everybody puts these whereever they want. There's really no standard place for driver-specific debugfs files to go, so putting it into some "subsystem"-specific directory seems like the better option.
Thierry