Re: [PATCH v4] media: v4l2-async: Add waiting subdevices debugfs

[Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>]

Hi Ezequiel,

On 15/01/2021 19:47, Kieran Bingham wrote:
> Hi Ezequiel,
> 
> On 15/01/2021 19:14, Ezequiel Garcia wrote:
>> There is currently little to no information available
>> about the reasons why a v4l2-async device hasn't
>> probed completely.
>>
>> Inspired by the "devices_deferred" debugfs file,
>> add a file to list information about the subdevices
>> that are on waiting lists, for each notifier.
>>
>> This is useful to debug v4l2-async subdevices
>> and notifiers, for instance when doing device bring-up.
>>
>> For instance, a typical output would be:
>>
>> $ cat /sys/kernel/debug/video4linux/pending_async_subdevices
>> ipu1_csi1:
>>  [fwnode] dev=20e0000.iomuxc-gpr:ipu1_csi1_mux, node=/soc/bus@2000000/iomuxc-gpr@20e0000/ipu1_csi1_mux
>> ipu1_csi0:
>>  [fwnode] dev=20e0000.iomuxc-gpr:ipu1_csi0_mux, node=/soc/bus@2000000/iomuxc-gpr@20e0000/ipu1_csi0_mux
>> imx6-mipi-csi2:
>>  [fwnode] dev=1-003c, node=/soc/bus@2100000/i2c@21a4000/camera@3c
>> imx-media:
> 
> Oh this is very exciting. I started looking at something like this
> recently, hitting async failures, and this already looks better.
> 
> In other words, - Thank you!
> 
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>


Throwing in an extra tag:

> root@salvator-x:/home/kbingham# cat /sys/kernel/debug/video4linux/pending_async_subdevices 
> max9286 4-006c:
>  [fwnode] dev=15-0035, node=/soc/i2c@e66d8000/gmsl-deserializer@6c/i2c-mux/i2c@0/camera@35/port/endpoint
> max9286 4-004c:
>  [fwnode] dev=10-0031, node=/soc/i2c@e66d8000/gmsl-deserializer@4c/i2c-mux/i2c@0/camera@31/port/endpoint
>  [fwnode] dev=11-0032, node=/soc/i2c@e66d8000/gmsl-deserializer@4c/i2c-mux/i2c@1/camera@32/port/endpoint
>  [fwnode] dev=12-0033, node=/soc/i2c@e66d8000/gmsl-deserializer@4c/i2c-mux/i2c@2/camera@33/port/endpoint
>  [fwnode] dev=13-0034, node=/soc/i2c@e66d8000/gmsl-deserializer@4c/i2c-mux/i2c@3/camera@34/port/endpoint
> rcar-vin e6ef7000.video:
> rcar_csi2 feab0000.csi2:
> rcar_csi2 feaa0000.csi2:
> rcar_csi2 fea80000.csi2:


That looks good and really helpful to me ;-)

Tested-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

> 
>> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
>> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>> ---
>>  drivers/media/v4l2-core/v4l2-async.c | 63 ++++++++++++++++++++++++++++
>>  drivers/media/v4l2-core/v4l2-dev.c   |  5 +++
>>  include/media/v4l2-async.h           |  8 ++++
>>  3 files changed, 76 insertions(+)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
>> index e3ab003a6c85..e35f18706792 100644
>> --- a/drivers/media/v4l2-core/v4l2-async.c
>> +++ b/drivers/media/v4l2-core/v4l2-async.c
>> @@ -5,6 +5,7 @@
>>   * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
>>   */
>>  
>> +#include <linux/debugfs.h>
>>  #include <linux/device.h>
>>  #include <linux/err.h>
>>  #include <linux/i2c.h>
>> @@ -14,6 +15,7 @@
>>  #include <linux/mutex.h>
>>  #include <linux/of.h>
>>  #include <linux/platform_device.h>
>> +#include <linux/seq_file.h>
>>  #include <linux/slab.h>
>>  #include <linux/types.h>
>>  
>> @@ -837,3 +839,64 @@ void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
>>  	mutex_unlock(&list_lock);
>>  }
>>  EXPORT_SYMBOL(v4l2_async_unregister_subdev);
>> +
>> +static void print_waiting_subdev(struct seq_file *s,
>> +				 struct v4l2_async_subdev *asd)
>> +{
>> +	switch (asd->match_type) {
>> +	case V4L2_ASYNC_MATCH_I2C:
>> +		seq_printf(s, " [i2c] dev=%d-%04x\n", asd->match.i2c.adapter_id,
>> +			   asd->match.i2c.address);
>> +		break;
>> +	case V4L2_ASYNC_MATCH_FWNODE: {
>> +		struct fwnode_handle *devnode, *fwnode = asd->match.fwnode;
>> +
>> +		devnode = fwnode_graph_is_endpoint(fwnode) ?
>> +			  fwnode_graph_get_port_parent(fwnode) :
>> +			  fwnode_handle_get(fwnode);
>> +
>> +		seq_printf(s, " [fwnode] dev=%s, node=%pfw\n",
>> +			   devnode->dev ? dev_name(devnode->dev) : "nil",
>> +			   fwnode);
>> +
>> +		fwnode_handle_put(devnode);
>> +		break;
>> +	}
>> +	}
>> +}
>> +
>> +static const char *
>> +v4l2_async_notifier_name(struct v4l2_async_notifier *notifier)
>> +{
>> +	if (notifier->v4l2_dev)
>> +		return notifier->v4l2_dev->name;
>> +	else if (notifier->sd)
>> +		return notifier->sd->name;
>> +	else
>> +		return "nil";
>> +}
>> +
>> +static int pending_subdevs_show(struct seq_file *s, void *data)
>> +{
>> +	struct v4l2_async_notifier *notif;
>> +	struct v4l2_async_subdev *asd;
>> +
>> +	mutex_lock(&list_lock);
>> +
>> +	list_for_each_entry(notif, &notifier_list, list) {
>> +		seq_printf(s, "%s:\n", v4l2_async_notifier_name(notif));
>> +		list_for_each_entry(asd, &notif->waiting, list)
>> +			print_waiting_subdev(s, asd);
>> +	}
>> +
>> +	mutex_unlock(&list_lock);
>> +
>> +	return 0;
>> +}
>> +DEFINE_SHOW_ATTRIBUTE(pending_subdevs);
>> +
>> +void v4l2_async_debug_init(struct dentry *debugfs_dir)
>> +{
>> +	debugfs_create_file("pending_async_subdevices", 0444, debugfs_dir, NULL,
>> +			    &pending_subdevs_fops);
>> +}
>> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
>> index f9cff033d0dc..b6a72d297775 100644
>> --- a/drivers/media/v4l2-core/v4l2-dev.c
>> +++ b/drivers/media/v4l2-core/v4l2-dev.c
>> @@ -14,6 +14,7 @@
>>  
>>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>>  
>> +#include <linux/debugfs.h>
>>  #include <linux/module.h>
>>  #include <linux/types.h>
>>  #include <linux/kernel.h>
>> @@ -38,6 +39,7 @@
>>  		       __func__, ##arg);				\
>>  } while (0)
>>  
>> +static struct dentry *v4l2_debugfs_dir;
>>  
>>  /*
>>   *	sysfs stuff
>> @@ -1118,6 +1120,8 @@ static int __init videodev_init(void)
>>  		return -EIO;
>>  	}
>>  
>> +	v4l2_debugfs_dir = debugfs_create_dir("video4linux", NULL);
>> +	v4l2_async_debug_init(v4l2_debugfs_dir);
>>  	return 0;
>>  }
>>  
>> @@ -1125,6 +1129,7 @@ static void __exit videodev_exit(void)
>>  {
>>  	dev_t dev = MKDEV(VIDEO_MAJOR, 0);
>>  
>> +	debugfs_remove_recursive(v4l2_debugfs_dir);
>>  	class_unregister(&video_class);
>>  	unregister_chrdev_region(dev, VIDEO_NUM_DEVICES);
>>  }
>> diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
>> index 0e04b5b2ebb0..243ac10a53c6 100644
>> --- a/include/media/v4l2-async.h
>> +++ b/include/media/v4l2-async.h
>> @@ -11,6 +11,7 @@
>>  #include <linux/list.h>
>>  #include <linux/mutex.h>
>>  
>> +struct dentry;
>>  struct device;
>>  struct device_node;
>>  struct v4l2_device;
>> @@ -137,6 +138,13 @@ struct v4l2_async_notifier {
>>  	struct list_head list;
>>  };
>>  
>> +/**
>> + * v4l2_async_debug_init - Initialize debugging tools.
>> + *
>> + * @debugfs_dir: pointer to the parent debugfs &struct dentry
>> + */
>> +void v4l2_async_debug_init(struct dentry *debugfs_dir);
>> +
>>  /**
>>   * v4l2_async_notifier_init - Initialize a notifier.
>>   *
>>
>