linux-kernel - Re: [PATCH v2] component: add debugfs support

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Date:   Thu, 16 Nov 2017 13:39:53 +0100
From:   Maciej Purski <m.purski@...sung.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Russell King <rmk+kernel@...linux.org.uk>
Cc:     linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v2] component: add debugfs support



On 11/15/2017 03:01 PM, Greg Kroah-Hartman wrote:
> On Wed, Nov 15, 2017 at 01:05:26PM +0100, Maciej Purski wrote:
>> Add 'component' directory to debugfs. Create a new file for each master,
>> when a master is added. Remove it on a master deletion.
>>
>> Show a list of devices matched with master and indicate if
>> master's components were successfully added and if the whole master is
>> bound.
>>
>> Signed-off-by: Maciej Purski <m.purski@...sung.com>
>> ---
>> Changes in v2:
>> - use seq_printf() instead of seq_puts() when printing headers
>> - move whole debugfs code to the file beginning in order to avoid
>>    forward declarations or using multiple ifdefs
>> ---
>>   drivers/base/component.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 83 insertions(+)
>>
>> diff --git a/drivers/base/component.c b/drivers/base/component.c
>> index 89b032f..8745ad9 100644
>> --- a/drivers/base/component.c
>> +++ b/drivers/base/component.c
>> @@ -17,6 +17,7 @@
>>   #include <linux/module.h>
>>   #include <linux/mutex.h>
>>   #include <linux/slab.h>
>> +#include <linux/debugfs.h>
>>   
>>   struct component;
>>   
>> @@ -41,6 +42,7 @@ struct master {
>>   	const struct component_master_ops *ops;
>>   	struct device *dev;
>>   	struct component_match *match;
>> +	struct dentry *dentry;
>>   };
>>   
>>   struct component {
>> @@ -56,6 +58,85 @@ static DEFINE_MUTEX(component_mutex);
>>   static LIST_HEAD(component_list);
>>   static LIST_HEAD(masters);
>>   
>> +#ifdef CONFIG_DEBUG_FS
>> +
>> +static struct dentry *component_debugfs_dir;
>> +
>> +static int component_devices_show(struct seq_file *s, void *data)
>> +{
>> +	struct master *m = s->private;
>> +	struct component_match *match = m->match;
>> +	size_t i;
>> +
>> +	mutex_lock(&component_mutex);
>> +	seq_printf(s, "%-40s %20s\n", "master name", "status");
>> +	seq_puts(s, "-------------------------------------------------------------\n");
>> +	seq_printf(s, "%-40s %20s\n\n",
>> +		   dev_name(m->dev), m->bound ? "bound" : "not bound");
>> +
>> +	seq_printf(s, "%-40s %20s\n", "device name", "status");
>> +	seq_puts(s, "-------------------------------------------------------------\n");
>> +	for (i = 0; i < match->num; i++) {
>> +		struct device *d = (struct device *)match->compare[i].data;
>> +
>> +		seq_printf(s, "%-40s %20s\n", dev_name(d),
>> +			   match->compare[i].component ?
>> +			   "registered" : "not registered");
>> +	}
>> +	mutex_unlock(&component_mutex);
>> +
>> +	return 0;
>> +}
>> +
>> +static int component_devices_open(struct inode *inode, struct file *file)
>> +{
>> +	return single_open(file, component_devices_show, inode->i_private);
>> +}
>> +
>> +static const struct file_operations component_devices_fops = {
>> +	.open = component_devices_open,
>> +	.read = seq_read,
>> +	.llseek = seq_lseek,
>> +	.release = single_release,
>> +};
>> +
>> +static int __init component_debug_init(void)
>> +{
>> +	component_debugfs_dir = debugfs_create_dir("component", NULL);
>> +
>> +	if (!component_debugfs_dir)
>> +		return -ENOMEM;
> 
> No need to test this at all, you should never fail anything if debugfs
> is not working properly, just continue and move on.  The result of any
> debugfs call can be fed back into any other debugfs call without any
> problems.
> 
>> +
>> +	return 0;
>> +}
>> +
>> +core_initcall(component_debug_init);
>> +
>> +static void component_master_debugfs_add(struct master *m)
>> +{
>> +	m->dentry = debugfs_create_file(dev_name(m->dev), 0444,
>> +					component_debugfs_dir,
>> +					m, &component_devices_fops);
> 
> See, you do it well here, do the same thing when you create the initial
> debugfs directory.

I'll to this the way you suggest. Thanks.

> 
> Also, "component" is very vague, can you think of a better term for
> this?  "device_component"?  "dev_component"?  Something else?  But I
> don't care, if you really like "component", that's fine.
>

I'm not really attached to that name, so I can change it to one that you suggested.
Maybe Russell King has some preference on that?

Best regards,

Maciej Purski

> thanks,
> 
> greg k-h
> 
> 
>