[PATCH v3 0/5] media: Add fdinfo support for v4l2 drivers

[Detlev Casanova]

fdinfo is useful to poll information from the driver.
Unlike the ftrace interface, it lets userspace tools get a snapshot of
the state of the driver at their own pace, instead of getting events for
each driver status change.

This works better to get information like HW usage time or clock
frequencies, as well as memory usage.
This patch set focuses on mem2mem drivers that are per-frame based and
an implementation is proposed for the Verisilicon Hantro and Rockchip
rkvdec drivers, limited to main clock frequency and HW usage time, as
well as HW cycles counting in Hantro.

Even though it is not used yet, per core fields are appended with 
`-<core_id>` to support multi-core drivers.

To ease support in drivers, a v4l2_metrics struct is added.
It stores metrics information and provides helper functions to write
the fdinfo file in a standard way.

An example of usage of this from userspace is implemented in v4l2top:

https://github.com/cazou/v4l2top (Check the upstream branch)

checkpatch.pl warning: The 2 arguments in the show_fdinfo callback
definition are kept unnamed to match with the rest of the struct
definition.

Signed-off-by: Detlev Casanova <detlev.casanova at collabora.com>
---
Changes in v3:
- Rename the fdinfo key prefix from "media-" to "v4l2-", and "stats" to
  "metrics"
- Restructure the documentation to have mandatory and optional keys
- Add core ID to fields
- Add HW cycles count support
- Add ABI documentation
- Link to v2: https://patch.msgid.link/20260617-v4l2-add-fdinfo-v2-0-d298e98ce06a@collabora.com

Changes in v2:
- Simplify key/value pairs by removing repeated <eng> suffix
- Add media type support
- Add v4l2_stats helpers
- Add support in rkvdec too
- Link to v1: https://patch.msgid.link/20260612-v4l2-add-fdinfo-v1-0-723211abc861@collabora.com

To: Mauro Carvalho Chehab <mchehab at kernel.org>
To: Nicolas Dufresne <nicolas.dufresne at collabora.com>
To: Benjamin Gaignard <benjamin.gaignard at collabora.com>
To: Philipp Zabel <p.zabel at pengutronix.de>
To: Detlev Casanova <detlev.casanova at collabora.com>
To: Ezequiel Garcia <ezequiel at vanguardiasur.com.ar>
To: Heiko Stuebner <heiko at sntech.de>
Cc: kernel at collabora.com
Cc: linux-media at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: linux-rockchip at lists.infradead.org
Cc: linux-arm-kernel at lists.infradead.org

---
Christopher Healy (2):
      docs: media: add documentation for V4L2 driver usage metrics
      media: hantro: Add per-context fdinfo usage metrics

Detlev Casanova (3):
      media: v4l2: Add callback for show_fdinfo
      media: v4l2-core: Add v4l2-metrics interface
      media: rkvdec: Add per-context fdinfo usage metrics

 Documentation/ABI/testing/procfs-fdinfo-v4l2       | 129 +++++++++++++++++++
 .../userspace-api/media/drivers/index.rst          |   1 +
 .../media/drivers/v4l2-usage-metrics.rst           | 137 +++++++++++++++++++++
 drivers/media/platform/rockchip/rkvdec/rkvdec.c    |  19 +++
 drivers/media/platform/rockchip/rkvdec/rkvdec.h    |   1 +
 drivers/media/platform/verisilicon/hantro.h        |   3 +
 drivers/media/platform/verisilicon/hantro_drv.c    |  19 +++
 drivers/media/platform/verisilicon/hantro_hw.h     |   1 +
 .../platform/verisilicon/rockchip_vpu981_regs.h    |   1 +
 .../media/platform/verisilicon/rockchip_vpu_hw.c   |   6 +
 drivers/media/v4l2-core/Makefile                   |   2 +-
 drivers/media/v4l2-core/v4l2-dev.c                 |  12 ++
 drivers/media/v4l2-core/v4l2-fh.c                  |   3 +
 drivers/media/v4l2-core/v4l2-metrics.c             |  78 ++++++++++++
 include/media/v4l2-dev.h                           |   1 +
 include/media/v4l2-fh.h                            |   2 +
 include/media/v4l2-metrics.h                       |  47 +++++++
 17 files changed, 461 insertions(+), 1 deletion(-)
---
base-commit: 3c587e0b08bd3c4853a22792b9166b7457870165
change-id: 20260610-v4l2-add-fdinfo-a790fceab329

Best regards,
--  
Detlev Casanova <detlev.casanova at collabora.com>