Re: [Linaro-mm-sig] [PATCH] dma-buf: Add debugfs support

[Maarten Lankhorst <m.b.lankhorst@gmail.com>]

Op 14-12-12 10:36, sumit.semwal@ti.com schreef:
> From: Sumit Semwal <sumit.semwal@linaro.org>
>
> Add debugfs support to make it easier to print debug information
> about the dma-buf buffers.
>
I like the idea, I don't know if it could be done in a free manner, but for bonus points
could we also have the dma-buf fd be obtainable that way from a debugfs entry?

Doing so would allow me to 'steal' a dma-buf from an existing mapping easily, and test against that.

Also I think the name of the device and process that exported the dma-buf would be useful
to have as well, even if in case of the device that would mean changing the api slightly to record it.

I was thinking of having a directory structure like this:

/sys/kernel/debug/dma_buf/stats

and then for each dma-buf:

/sys/kernel/debug/dma-buf/exporting_file.c/<number>-fd
/sys/kernel/debug/dma-buf/exporting_file.c/<number>-attachments
/sys/kernel/debug/dma-buf/exporting_file.c/<number>-info

Opening the fd file would give you back the original fd, or fail with -EIO if refcount was dropped to 0.

Would something like this be doable? I don't know debugfs that well, but I don't see why it wouldn't be,

~Maarten