On 06/27/2016 01:57 PM, Nick Dyer wrote:

Hi Hans-

Thanks for reviewing this again in such detail.

On 27/06/2016 12:26, Hans Verkuil wrote:

quoted

On 06/23/2016 12:08 AM, Nick Dyer wrote:

quoted

This is a series of patches to add output of raw touch diagnostic data via V4L2
to the Atmel maXTouch and Synaptics RMI4 drivers.

It's a rewrite of the previous implementation which output via debugfs: it now
uses a V4L2 device in a similar way to the sur40 driver.

We have a utility which can read the data and display it in a useful format:
    https://github.com/ndyer/heatmap/commits/heatmap-v4l

These patches are also available from
    https://github.com/ndyer/linux/commits/v4l-touch-2016-06-22

Changes in v5 (Hans Verkuil review):
- Update v4l2-core:
  - Add VFL_TYPE_TOUCH, V4L2_BUF_TYPE_TOUCH_CAPTURE and V4L2_CAP_TOUCH

The use of V4L2_CAP_TOUCH and V4L2_BUF_TYPE_TOUCH_CAPTURE is very inconsistent.
What is the rationale of adding V4L2_BUF_TYPE_TOUCH_CAPTURE? I can't remember
asking for it.

I am afraid that I missed updating atmel_mxt_ts from
V4L2_BUF_TYPE_VIDEO_CAPTURE to V4L2_BUF_TYPE_TOUCH_CAPTURE, which has
confused the situation.

Perhaps I read too much into your request that I look at the way that SDR
is treated. When I started going through the code paths in v4l2-core and
v4l2-compliance, it seemed cleaner to treat touch as completely separate,
hence introducing the new BUF_TYPE. I'm happy to try it without this.

Yeah, I didn't mean that you had to add a new BUF_TYPE. My remark was related to
ensuring that all occurrences in the spec where they talk about the various
/dev/video/radio/etc. devices are extended with v4l-touch as well.

quoted

And wouldn't the use of V4L2_BUF_TYPE_TOUCH_CAPTURE break userspace for sur40?

I think it is likely, yes. And it looks like that would make Florian unhappy.

quoted

I'm ambiguous towards having a V4L2_BUF_TYPE_TOUCH_CAPTURE, to be honest.

I would also recommend renaming V4L2_CAP_TOUCH to V4L2_CAP_TOUCH_CAPTURE.

Do you agree with the following changes:

- Rename V4L2_CAP_TOUCH to V4L2_CAP_TOUCH_CAPTURE.

- Touch devices should register both V4L2_CAP_VIDEO_CAPTURE and
V4L2_CAP_TOUCH_CAPTURE.

- Get rid of V4L2_BUF_TYPE_TOUCH_CAPTURE and use
V4L2_BUF_TYPE_VIDEO_CAPTURE. In v4l2-ioctl.c if we need to force particular
pix formats for touch, it will need to look at V4L2_CAP_TOUCH_CAPTURE.

Actually, I think we have two choices, depending on whether we use a
BUF_TYPE_TOUCH_CAPTURE or not.

1) If we go with a BUF_TYPE_TOUCH_CAPTURE, then:

- we need a V4L2_CAP_TOUCH_CAPTURE
- no V4L2_CAP_VIDEO_CAPTURE will be set (since that would indicate support for
  BUF_TYPE_VIDEO_CAPTURE, which we don't have anymore).
- new callbacks for g/s/try/enum_fmt_tch_cap should be added to v4l2-ioctl.h.

2) Alternatively, if we want to keep using BUF_TYPE_VIDEO_CAPTURE, then:

- we keep V4L2_CAP_TOUCH which is combined with CAP_VIDEO_CAPTURE (and perhaps
  VIDEO_OUTPUT in the future). The CAP_TOUCH just says that this is a touch
  device, not a video device, but otherwise it acts the same.

I'd go with 2, since I see no reason to add a new BUF_TYPE for this.
It acts exactly like video after all, with only a few restrictions (i.e. no
colorspace info or interlaced). And adding a new BUF_TYPE will likely break
the existing sur40 app.

Your other review comments look straightforward to address - thanks.

I should say, you can see my current changes to v4l2-compliance here:
https://github.com/ndyer/v4l-utils/commit/07e00c33

Should I post them along with the kernel patches next time?

Yes, please.

Regards,

	Hans

quoted

I can imagine an embedded usb gadget device that outputs touch data to a PC.

Regards,

	Hans

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