Message-Id: <201301091642.38184.hverkuil@xs4all.nl>
Date:	Wed, 9 Jan 2013 16:42:38 +0100
From:	Hans Verkuil <hverkuil@...all.nl>
To:	"Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:	LMML <linux-media@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Hans Verkuil <hans.verkuil@...co.com>,
	Sekhar Nori <nsekhar@...com>,
	DLOS <davinci-linux-open-source@...ux.davincidsp.com>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	"Lad, Prabhakar" <prabhakar.lad@...com>,
	Sakari Ailus <sakari.ailus@....fi>,
	Mauro Carvalho Chehab <mchehab@...hat.com>
Subject: Re: [PATCH RFC 1/3] davinci: vpif: capture: add V4L2-async support

On Wed 9 January 2013 14:41:25 Lad, Prabhakar wrote:
> Add support for asynchronous subdevice probing, using the v4l2-async API.
> The legacy synchronous mode is still supported too, which allows to
> gradually update drivers and platforms. The selected approach adds a
> notifier for each struct soc_camera_device instance, i.e. for each video
> device node, even when there are multiple such instances registered with a
> single soc-camera host simultaneously.

This comment was obviously copy-and-pasted from somewhere else :-)

> 
> Signed-off-by: Lad, Prabhakar <prabhakar.lad@...com>
> Cc: Guennadi Liakhovetski <g.liakhovetski@....de>
> Cc: Hans Verkuil <hans.verkuil@...co.com>
> Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Cc: Sakari Ailus <sakari.ailus@....fi>
> Cc: Mauro Carvalho Chehab <mchehab@...hat.com>
> ---
>  drivers/media/platform/davinci/vpif_capture.c |  171 ++++++++++++++++++-------
>  drivers/media/platform/davinci/vpif_capture.h |    2 +
>  include/media/davinci/vpif_types.h            |    2 +
>  3 files changed, 128 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/media/platform/davinci/vpif_capture.c b/drivers/media/platform/davinci/vpif_capture.c
> index 5892d2b..a8b6588 100644
> --- a/drivers/media/platform/davinci/vpif_capture.c
> +++ b/drivers/media/platform/davinci/vpif_capture.c
> @@ -34,6 +34,8 @@
>  #include <linux/platform_device.h>
>  #include <linux/io.h>
>  #include <linux/slab.h>
> +
> +#include <media/v4l2-async.h>
>  #include <media/v4l2-device.h>
>  #include <media/v4l2-ioctl.h>
>  #include <media/v4l2-chip-ident.h>
> @@ -2054,6 +2056,96 @@ vpif_init_free_channel_objects:
>  	return err;
>  }
>  
> +int vpif_async_bound(struct v4l2_async_notifier *notifier,
> +		    struct v4l2_async_subdev_list *asdl)
> +{
> +	int i = 0;
> +
> +	if (!asdl->subdev) {
> +		v4l2_err(vpif_dev->driver,
> +			 "%s(): Subdevice driver hasn't set subdev pointer!\n",
> +			__func__);
> +		return -EINVAL;
> +	}
> +	v4l2_info(&vpif_obj.v4l2_dev, "registered sub device %s\n",
> +			 asdl->subdev->name);

This v4l2_info shouldn't be necessary: when the subdev is loaded it will already
report that it is registered, so this would just duplicate things.

> +
> +	for (i = 0; i < vpif_obj.config->subdev_count; i++)
> +		if (!strcmp(vpif_obj.config->subdev_info[i].name,
> +			asdl->subdev->name)) {
> +			vpif_obj.sd[i] = asdl->subdev;
> +			break;
> +		}
> +
> +	if (i >= vpif_obj.config->subdev_count)
> +		return -EINVAL;
> +
> +	return 0;

This function feels unnecessary. What you basically do here is to fill in
the vpif_obj.sd[i] pointer. Wouldn't it be easier if we added a function to
v4l2-device.c that will return a v4l2_subdev pointer based on the subdev name
or possibly that of a struct v4l2_async_hw_device by walking the subdevice
list that is stored in v4l2_device?

Then you could do something like this in vpif_probe_complete:

	for (i = 0; i < vpif_obj.config->subdev_count; i++)
		vpif_obj.sd[i] = v4l2_device_get_subdev_by_name(v4l2_dev,
					vpif_obj.config->subdev_info[i].name);

and there would be no need for a bound callback.

Passing a struct v4l2_async_hw_device can be useful too: then you can
walk the list of subdevs passed in struct v4l2_async_notifier and you
don't need to fiddle with subdev names.

It's just a suggestion, but I think it will improve the code as the control
flow is more logical that way (async callbacks are always harder to understand).

> +}
> +
> +static int vpif_probe_complete(void)
> +{
> +	struct common_obj *common;
> +	struct channel_obj *ch;
> +	int i, j, err, k;
> +
> +	for (j = 0; j < VPIF_CAPTURE_MAX_DEVICES; j++) {
> +		ch = vpif_obj.dev[j];
> +		ch->channel_id = j;
> +		common = &(ch->common[VPIF_VIDEO_INDEX]);
> +		spin_lock_init(&common->irqlock);
> +		mutex_init(&common->lock);
> +		ch->video_dev->lock = &common->lock;
> +		/* Initialize prio member of channel object */
> +		v4l2_prio_init(&ch->prio);
> +		video_set_drvdata(ch->video_dev, ch);
> +
> +		/* select input 0 */
> +		err = vpif_set_input(vpif_obj.config, ch, 0);
> +		if (err)
> +			goto probe_out;
> +
> +		err = video_register_device(ch->video_dev,
> +					    VFL_TYPE_GRABBER, (j ? 1 : 0));
> +		if (err)
> +			goto probe_out;
> +	}
> +
> +	v4l2_info(&vpif_obj.v4l2_dev, "VPIF capture driver initialized\n");
> +	return 0;
> +
> +probe_out:
> +	for (k = 0; k < j; k++) {
> +		/* Get the pointer to the channel object */
> +		ch = vpif_obj.dev[k];
> +		/* Unregister video device */
> +		video_unregister_device(ch->video_dev);
> +	}
> +	kfree(vpif_obj.sd);
> +	for (i = 0; i < VPIF_CAPTURE_MAX_DEVICES; i++) {
> +		ch = vpif_obj.dev[i];
> +		/* Note: does nothing if ch->video_dev == NULL */
> +		video_device_release(ch->video_dev);
> +	}
> +	v4l2_device_unregister(&vpif_obj.v4l2_dev);
> +
> +	return err;
> +}
> +
> +int vpif_async_complete(struct v4l2_async_notifier *notifier)
> +{
> +	return vpif_probe_complete();

Why this extra indirection? I'd remove it.

> +}
> +
> +void vpif_async_unbind(struct v4l2_async_notifier *notifier,
> +		    struct v4l2_async_subdev_list *asdl)
> +{
> +	/*FIXME: Do we need this callback ? */

I think this callback can be removed.

> +	v4l2_info(&vpif_obj.v4l2_dev, "unregistered sub device %s\n",
> +			 asdl->subdev->name);
> +	return;
> +}
> +
>  /**
>   * vpif_probe : This function probes the vpif capture driver
>   * @pdev: platform device pointer
> @@ -2064,12 +2156,10 @@ vpif_init_free_channel_objects:
>  static __init int vpif_probe(struct platform_device *pdev)
>  {
>  	struct vpif_subdev_info *subdevdata;
> -	struct vpif_capture_config *config;
> -	int i, j, k, err;
> +	int i, j, err;
>  	int res_idx = 0;
>  	struct i2c_adapter *i2c_adap;
>  	struct channel_obj *ch;
> -	struct common_obj *common;
>  	struct video_device *vfd;
>  	struct resource *res;
>  	int subdev_count;
> @@ -2146,10 +2236,9 @@ static __init int vpif_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> -	i2c_adap = i2c_get_adapter(1);
> -	config = pdev->dev.platform_data;
> +	vpif_obj.config = pdev->dev.platform_data;
>  
> -	subdev_count = config->subdev_count;
> +	subdev_count = vpif_obj.config->subdev_count;
>  	vpif_obj.sd = kzalloc(sizeof(struct v4l2_subdev *) * subdev_count,
>  				GFP_KERNEL);
>  	if (vpif_obj.sd == NULL) {
> @@ -2158,53 +2247,41 @@ static __init int vpif_probe(struct platform_device *pdev)
>  		goto vpif_sd_error;
>  	}
>  
> -	for (i = 0; i < subdev_count; i++) {
> -		subdevdata = &config->subdev_info[i];
> -		vpif_obj.sd[i] =
> -			v4l2_i2c_new_subdev_board(&vpif_obj.v4l2_dev,
> -						  i2c_adap,
> -						  &subdevdata->board_info,
> -						  NULL);
> +	if (!vpif_obj.config->asd_sizes) {
> +		i2c_adap = i2c_get_adapter(1);
> +		for (i = 0; i < subdev_count; i++) {
> +			subdevdata = &vpif_obj.config->subdev_info[i];
> +			vpif_obj.sd[i] =
> +				v4l2_i2c_new_subdev_board(&vpif_obj.v4l2_dev,
> +							i2c_adap,
> +							&subdevdata->board_info,
> +							NULL);
>  
> -		if (!vpif_obj.sd[i]) {
> -			vpif_err("Error registering v4l2 subdevice\n");
> -			goto probe_subdev_out;
> +			if (!vpif_obj.sd[i]) {
> +				vpif_err("Error registering v4l2 subdevice\n");
> +				goto probe_subdev_out;
> +			}
> +			v4l2_info(&vpif_obj.v4l2_dev, "registered sub device %s\n",
> +				subdevdata->name);
> +		}
> +		vpif_probe_complete();
> +	} else {
> +		vpif_obj.notifier.subdev = vpif_obj.config->asd;
> +		vpif_obj.notifier.subdev_num = vpif_obj.config->asd_sizes[0];
> +		vpif_obj.notifier.bound = vpif_async_bound;
> +		vpif_obj.notifier.complete = vpif_async_complete;
> +		vpif_obj.notifier.unbind = vpif_async_unbind;
> +		err = v4l2_async_notifier_register(&vpif_obj.v4l2_dev,
> +						   &vpif_obj.notifier);
> +		if (err) {
> +			vpif_err("Error registering async notifier\n");
> +			err = -EINVAL;
> +			goto vpif_sd_error;
>  		}
> -		v4l2_info(&vpif_obj.v4l2_dev, "registered sub device %s\n",
> -			  subdevdata->name);
>  	}
>  
> -	for (j = 0; j < VPIF_CAPTURE_MAX_DEVICES; j++) {
> -		ch = vpif_obj.dev[j];
> -		ch->channel_id = j;
> -		common = &(ch->common[VPIF_VIDEO_INDEX]);
> -		spin_lock_init(&common->irqlock);
> -		mutex_init(&common->lock);
> -		ch->video_dev->lock = &common->lock;
> -		/* Initialize prio member of channel object */
> -		v4l2_prio_init(&ch->prio);
> -		video_set_drvdata(ch->video_dev, ch);
> -
> -		/* select input 0 */
> -		err = vpif_set_input(config, ch, 0);
> -		if (err)
> -			goto probe_out;
> -
> -		err = video_register_device(ch->video_dev,
> -					    VFL_TYPE_GRABBER, (j ? 1 : 0));
> -		if (err)
> -			goto probe_out;
> -	}
> -	v4l2_info(&vpif_obj.v4l2_dev, "VPIF capture driver initialized\n");
>  	return 0;
>  
> -probe_out:
> -	for (k = 0; k < j; k++) {
> -		/* Get the pointer to the channel object */
> -		ch = vpif_obj.dev[k];
> -		/* Unregister video device */
> -		video_unregister_device(ch->video_dev);
> -	}
>  probe_subdev_out:
>  	/* free sub devices memory */
>  	kfree(vpif_obj.sd);
> diff --git a/drivers/media/platform/davinci/vpif_capture.h b/drivers/media/platform/davinci/vpif_capture.h
> index 3d3c1e5..1be47ab 100644
> --- a/drivers/media/platform/davinci/vpif_capture.h
> +++ b/drivers/media/platform/davinci/vpif_capture.h
> @@ -145,6 +145,8 @@ struct vpif_device {
>  	struct v4l2_device v4l2_dev;
>  	struct channel_obj *dev[VPIF_CAPTURE_NUM_CHANNELS];
>  	struct v4l2_subdev **sd;
> +	struct v4l2_async_notifier notifier;
> +	struct vpif_capture_config *config;
>  };
>  
>  struct vpif_config_params {
> diff --git a/include/media/davinci/vpif_types.h b/include/media/davinci/vpif_types.h
> index 3882e06..e08bcde 100644
> --- a/include/media/davinci/vpif_types.h
> +++ b/include/media/davinci/vpif_types.h
> @@ -81,5 +81,7 @@ struct vpif_capture_config {
>  	struct vpif_subdev_info *subdev_info;
>  	int subdev_count;
>  	const char *card_name;
> +	struct v4l2_async_subdev **asd;	/* Flat array, arranged in groups */
> +	int *asd_sizes;		/* 0-terminated array of asd group sizes */
>  };
>  #endif /* _VPIF_TYPES_H */
> 

Regards,

	Hans
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