Re: [Intel-gfx] [RFC 01/12] drm/i915: Expose list of clients in sysfs

From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, Intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [RFC 01/12] drm/i915: Expose list of clients in sysfs
Date: Tue, 10 Mar 2020 12:04:39 +0000	[thread overview]
Message-ID: <488dc425-7786-655d-3c8e-c5dc7bb61b1a@linux.intel.com> (raw)
In-Reply-To: <158384050785.16414.7982219438580665617@build.alporthouse.com>

On 10/03/2020 11:41, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2020-03-09 18:31:18)
>> +static int
>> +__i915_drm_client_register(struct i915_drm_client *client,
>> +                          struct task_struct *task)
>> +{
>> +       struct i915_drm_clients *clients = client->clients;
>> +       struct device_attribute *attr;
>> +       int ret = -ENOMEM;
>> +       char idstr[32];
>> +
>> +       client->pid = get_task_pid(task, PIDTYPE_PID);
>> +
>> +       client->name = kstrdup(task->comm, GFP_KERNEL);
>> +       if (!client->name)
>> +               goto err_name;
>> +
>> +       if (!clients->root)
>> +               return 0; /* intel_fbdev_init registers a client before sysfs */
>> +
>> +       snprintf(idstr, sizeof(idstr), "%u", client->id);
>> +       client->root = kobject_create_and_add(idstr, clients->root);
>> +       if (!client->root)
>> +               goto err_client;
>> +
>> +       attr = &client->attr.name;
>> +       sysfs_attr_init(&attr->attr);
>> +       attr->attr.name = "name";
>> +       attr->attr.mode = 0444;
>> +       attr->show = show_client_name;
>> +
>> +       ret = sysfs_create_file(client->root, (struct attribute *)attr);
>> +       if (ret)
>> +               goto err_attr;
>> +
>> +       attr = &client->attr.pid;
>> +       sysfs_attr_init(&attr->attr);
>> +       attr->attr.name = "pid";
>> +       attr->attr.mode = 0444;
>> +       attr->show = show_client_pid;
>> +
>> +       ret = sysfs_create_file(client->root, (struct attribute *)attr);
>> +       if (ret)
>> +               goto err_attr;
> 
> How do we think we will extend this (e.g. for client/1/(trace,debug))?
> 
> i915_drm_client_add_attr() ?
> 
> Or should we put all the attr here and make them known a priori?
> 
> I think I prefer i915_drm_client_add_attr, but that will also require a
> notification chain? And that smells like overengineering.
> 
> At any rate we have 2 other definite users around the corner for the
> client sysfs, so we should look at what API suits us.

It sounds acceptable to me to just call their setup from here. 
__i915_drm_client_register sounds clear enough place.

We potentially just split the function into "client core" and "add-on 
users" for better readability:

__i915_drm_client_register
{
	...register_client();

	...register_client_busy(client, ...);

	...register_client_xxx(client, ...);
}

Regards,

Tvrtko
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