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Date: Tue, 30 May 2017 09:56:32 +0300
From: Sakari Ailus <sakari.ailus@iki.fi>
To: Steve Longerbeam <slongerbeam@gmail.com>
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        Steve Longerbeam <steve_longerbeam@mentor.com>
Subject: Re: [PATCH v7 16/34] [media] add Omnivision OV5640 sensor driver
Message-ID: <20170530065632.GK29527@valkosipuli.retiisi.org.uk>
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Hi Steve,

On Mon, May 29, 2017 at 02:50:34PM -0700, Steve Longerbeam wrote:
> ><snip>
> >
> >>+
> >>+static int ov5640_s_ctrl(struct v4l2_ctrl *ctrl)
> >>+{
> >>+	struct v4l2_subdev *sd = ctrl_to_sd(ctrl);
> >>+	struct ov5640_dev *sensor = to_ov5640_dev(sd);
> >>+	int ret = 0;
> >>+
> >>+	mutex_lock(&sensor->lock);
> >Could you use the same lock for the controls as you use for the rest? Just
> >setting handler->lock after handler init does the trick.
> 
> Can you please rephrase, I don't follow. "same lock for the controls as
> you use for the rest" - there's only one device lock owned by this driver
> and I am already using that same lock.

There's another in the control handler. You could use your own lock for the
control handler as well.

> 
> 
> ><snip>
> >>+
> >>+static int ov5640_s_stream(struct v4l2_subdev *sd, int enable)
> >>+{
> >>+	struct ov5640_dev *sensor = to_ov5640_dev(sd);
> >>+	int ret = 0;
> >>+
> >>+	mutex_lock(&sensor->lock);
> >>+
> >>+#if defined(CONFIG_MEDIA_CONTROLLER)
> >>+	if (sd->entity.stream_count > 1)
> >The entity stream_count isn't connected to the number of times s_stream(sd,
> >true) is called. Please remove the check.
> 
> It's incremented by media_pipeline_start(), even if the entity is already
> a member of the given pipeline.
> 
> I added this check because in imx-media, the ov5640 can be streaming
> concurrently to multiple video capture devices, and each capture device
> calls
> media_pipeline_start() at stream on, which increments the entity stream
> count.
> 
> So if one capture device issues a stream off while others are still
> streaming,
> ov5640 should remain at stream on. So the entity stream count is being
> used as a streaming usage counter. Is there a better way to do this? Should
> I use a private stream use counter instead?

Different drivers may use media_pipeline_start() in different ways. Stream
control shouldn't depend on that count. This could cause issues in using the
driver with other ISP / receiver drivers.

I think it should be enough to move the check to the imx driver in this
case.

> 
> 
> 
> ><snip>
> >
> >>+
> >>+free_ctrls:
> >>+	v4l2_ctrl_handler_free(&sensor->ctrls.handler);
> >>+entity_cleanup:
> >>+	mutex_destroy(&sensor->lock);
> >>+	media_entity_cleanup(&sensor->sd.entity);
> >>+	regulator_bulk_disable(OV5640_NUM_SUPPLIES, sensor->supplies);
> >Should this still be here?
> >
> >>+	return ret;
> >>+}
> >>+
> >>+static int ov5640_remove(struct i2c_client *client)
> >>+{
> >>+	struct v4l2_subdev *sd = i2c_get_clientdata(client);
> >>+	struct ov5640_dev *sensor = to_ov5640_dev(sd);
> >>+
> >>+	regulator_bulk_disable(OV5640_NUM_SUPPLIES, sensor->supplies);
> >Ditto.
> 
> I don't understand. regulator_bulk_disable() is still needed, am I missing
> something?

You still need to enable it first. I don't see that being done in probe. As
the driver implements the s_power() op, I don't see a need for powering the
device on at probe time (and conversely off at remove time).

-- 
Regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi	XMPP: sailus@retiisi.org.uk