Re: [PATCH v4 5/9] drm/client: Add client callbacks

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jul 03, 2018 at 03:07:50PM +0200, Noralf Trønnes wrote:
> 
> Den 03.07.2018 09.46, skrev Daniel Vetter:
> > On Mon, Jul 02, 2018 at 03:54:29PM +0200, Noralf Trønnes wrote:
> > > Add client callbacks and hook them up.
> > > Add a list of clients per drm_device.
> > > 
> > > Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> > btw for reviewing it'd be simpler if you merge the 2 patches that add the
> > client library, avoids me having to jump back&forth ..
> > 
> > Bunch of comments below still.
> > -Daniel
> > 
> > > ---
> > >   drivers/gpu/drm/drm_client.c        | 92 ++++++++++++++++++++++++++++++++++++-
> > >   drivers/gpu/drm/drm_drv.c           |  7 +++
> > >   drivers/gpu/drm/drm_fb_cma_helper.c |  2 +-
> > >   drivers/gpu/drm/drm_fb_helper.c     | 11 ++++-
> > >   drivers/gpu/drm/drm_file.c          |  3 ++
> > >   drivers/gpu/drm/drm_probe_helper.c  |  3 ++
> > >   include/drm/drm_client.h            | 75 +++++++++++++++++++++++++++++-
> > >   include/drm/drm_device.h            | 14 ++++++
> > >   8 files changed, 201 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> > > index 9c9b8ac7aea3..f05ee98bd10c 100644
> > > --- a/drivers/gpu/drm/drm_client.c
> > > +++ b/drivers/gpu/drm/drm_client.c
> > > @@ -4,6 +4,7 @@
> > >    */
> > >   #include <linux/list.h>
> > > +#include <linux/module.h>
> > >   #include <linux/mutex.h>
> > >   #include <linux/seq_file.h>
> > >   #include <linux/slab.h>
> > > @@ -66,6 +67,7 @@ EXPORT_SYMBOL(drm_client_close);
> > >    * @dev: DRM device
> > >    * @client: DRM client
> > >    * @name: Client name
> > > + * @funcs: DRM client functions (optional)
> > >    *
> > >    * Use drm_client_put() to free the client.
> > >    *
> > > @@ -73,24 +75,47 @@ EXPORT_SYMBOL(drm_client_close);
> > >    * Zero on success or negative error code on failure.
> > >    */
> > >   int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
> > > -		   const char *name)
> > > +		   const char *name, const struct drm_client_funcs *funcs)
> > >   {
> > > +	bool registered;
> > >   	int ret;
> > >   	if (!drm_core_check_feature(dev, DRIVER_MODESET) ||
> > >   	    !dev->driver->dumb_create || !dev->driver->gem_prime_vmap)
> > >   		return -ENOTSUPP;
> > > +	if (funcs && !try_module_get(funcs->owner))
> > > +		return -ENODEV;
> > > +
> > >   	client->dev = dev;
> > >   	client->name = name;
> > > +	client->funcs = funcs;
> > >   	ret = drm_client_open(client);
> > >   	if (ret)
> > > -		return ret;
> > > +		goto err_put_module;
> > > +
> > > +	mutex_lock(&dev->clientlist_mutex);
> > > +	registered = dev->registered;
> > > +	if (registered)
> > > +		list_add(&client->list, &dev->clientlist);
> > > +	mutex_unlock(&dev->clientlist_mutex);
> > > +	if (!registered) {
> > > +		ret = -ENODEV;
> > > +		goto err_close;
> > > +	}
> > >   	drm_dev_get(dev);
> > This only works if the caller holds a reference for us on dev already, or
> > has some other guarantee that it won't disappear. Would be good to mention
> > this in the kerneldoc.
> > 
> > >   	return 0;
> > > +
> > > +err_close:
> > > +	drm_client_close(client);
> > > +err_put_module:
> > > +	if (funcs)
> > > +		module_put(funcs->owner);
> > > +
> > > +	return ret;
> > >   }
> > >   EXPORT_SYMBOL(drm_client_new);
> > > @@ -116,9 +141,72 @@ void drm_client_release(struct drm_client_dev *client)
> > >   	drm_client_close(client);
> > >   	drm_dev_put(dev);
> > > +	if (client->funcs)
> > > +		module_put(client->funcs->owner);
> > >   }
> > >   EXPORT_SYMBOL(drm_client_release);
> > > +void drm_client_dev_unregister(struct drm_device *dev)
> > > +{
> > > +	struct drm_client_dev *client, *tmp;
> > > +
> > > +	if (!drm_core_check_feature(dev, DRIVER_MODESET))
> > > +		return;
> > > +
> > > +	mutex_lock(&dev->clientlist_mutex);
> > > +	list_for_each_entry_safe(client, tmp, &dev->clientlist, list) {
> > > +		list_del(&client->list);
> > > +		if (client->funcs && client->funcs->unregister) {
> > > +			client->funcs->unregister(client);
> > Hm, not ->unregister is called while holding the lock. I thought that
> > blows up for you?
> 
> It is fine now that we decided that the client can't remove itself.
> Only the driver can do it on drm_dev_unregister().

I was more wondering about creating an unecessary locking hierarchy
complication. But through the ->hotplug and ->restore callbacks we already
require that all client locks (which will also include anything related to
fbdev and fbcon, hence also console_lock) must nest within
dev->clientlist_mutex. That's the part I was worried about, but that's not
a good concern really.

So all fine for me on 2nd thought.
> 
> > > +		} else {
> > > +			drm_client_release(client);
> > > +			kfree(client);
> > > +		}
> > > +	}
> > > +	mutex_unlock(&dev->clientlist_mutex);
> > > +}
> > > +
> > Needs a bit of kerneldoc here since exported function. Drivers might also
> > want to call this from their own hotplug handling.
> 
> drm_client_dev_hotplug() is only called by drm_kms_helper_hotplug_event().
> The reason it's exported is because the helper can be built as a module.

Anything helpers do drivers should be able to override. Anything drivers
should be able to use should have docs.

And e.g. drm_sysfs_hotplug_event is actually called by a driver namely
vmwgfx, and I think these two functions are pretty much equivalent - one
informs userspace clients about a hotplug, the other kernel clients about
a hotplug.

Anyway, since my only major concern (the locking question) is cleared up
after a bit more think I think this is good for an r-b, once the kerneldoc
is all fixed up and the ->release callback gone:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Cheers, Daniel

> 
> Noralf.
> 
> > > +void drm_client_dev_hotplug(struct drm_device *dev)
> > > +{
> > > +	struct drm_client_dev *client;
> > > +	int ret;
> > > +
> > > +	if (!drm_core_check_feature(dev, DRIVER_MODESET))
> > > +		return;
> > > +
> > > +	mutex_lock(&dev->clientlist_mutex);
> > > +	list_for_each_entry(client, &dev->clientlist, list) {
> > > +		if (!client->funcs || !client->funcs->hotplug)
> > > +			continue;
> > > +
> > > +		ret = client->funcs->hotplug(client);
> > > +		DRM_DEV_DEBUG_KMS(dev->dev, "%s: ret=%d\n", client->name, ret);
> > > +	}
> > > +	mutex_unlock(&dev->clientlist_mutex);
> > > +}
> > > +EXPORT_SYMBOL(drm_client_dev_hotplug);
> > > +
> > > +void drm_client_dev_restore(struct drm_device *dev)
> > > +{
> > > +	struct drm_client_dev *client;
> > > +	int ret;
> > > +
> > > +	if (!drm_core_check_feature(dev, DRIVER_MODESET))
> > > +		return;
> > > +
> > > +	mutex_lock(&dev->clientlist_mutex);
> > > +	list_for_each_entry(client, &dev->clientlist, list) {
> > > +		if (!client->funcs || !client->funcs->restore)
> > > +			continue;
> > > +
> > > +		ret = client->funcs->restore(client);
> > > +		DRM_DEV_DEBUG_KMS(dev->dev, "%s: ret=%d\n", client->name, ret);
> > > +		if (!ret) /* The first one to return zero gets the privilege to restore */
> > > +			break;
> > > +	}
> > > +	mutex_unlock(&dev->clientlist_mutex);
> > > +}
> > > +
> > >   static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
> > >   {
> > >   	struct drm_device *dev = buffer->client->dev;
> > > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > > index e7ff0b03328b..6eb935bb2f92 100644
> > > --- a/drivers/gpu/drm/drm_drv.c
> > > +++ b/drivers/gpu/drm/drm_drv.c
> > > @@ -34,6 +34,7 @@
> > >   #include <linux/slab.h>
> > >   #include <linux/srcu.h>
> > > +#include <drm/drm_client.h>
> > >   #include <drm/drm_drv.h>
> > >   #include <drm/drmP.h>
> > > @@ -506,6 +507,7 @@ int drm_dev_init(struct drm_device *dev,
> > >   	INIT_LIST_HEAD(&dev->filelist);
> > >   	INIT_LIST_HEAD(&dev->filelist_internal);
> > > +	INIT_LIST_HEAD(&dev->clientlist);
> > >   	INIT_LIST_HEAD(&dev->ctxlist);
> > >   	INIT_LIST_HEAD(&dev->vmalist);
> > >   	INIT_LIST_HEAD(&dev->maplist);
> > > @@ -515,6 +517,7 @@ int drm_dev_init(struct drm_device *dev,
> > >   	spin_lock_init(&dev->event_lock);
> > >   	mutex_init(&dev->struct_mutex);
> > >   	mutex_init(&dev->filelist_mutex);
> > > +	mutex_init(&dev->clientlist_mutex);
> > >   	mutex_init(&dev->ctxlist_mutex);
> > >   	mutex_init(&dev->master_mutex);
> > > @@ -570,6 +573,7 @@ int drm_dev_init(struct drm_device *dev,
> > >   err_free:
> > >   	mutex_destroy(&dev->master_mutex);
> > >   	mutex_destroy(&dev->ctxlist_mutex);
> > > +	mutex_destroy(&dev->clientlist_mutex);
> > >   	mutex_destroy(&dev->filelist_mutex);
> > >   	mutex_destroy(&dev->struct_mutex);
> > >   	return ret;
> > > @@ -604,6 +608,7 @@ void drm_dev_fini(struct drm_device *dev)
> > >   	mutex_destroy(&dev->master_mutex);
> > >   	mutex_destroy(&dev->ctxlist_mutex);
> > > +	mutex_destroy(&dev->clientlist_mutex);
> > >   	mutex_destroy(&dev->filelist_mutex);
> > >   	mutex_destroy(&dev->struct_mutex);
> > >   	kfree(dev->unique);
> > > @@ -859,6 +864,8 @@ void drm_dev_unregister(struct drm_device *dev)
> > >   	dev->registered = false;
> > > +	drm_client_dev_unregister(dev);
> > > +
> > >   	if (drm_core_check_feature(dev, DRIVER_MODESET))
> > >   		drm_modeset_unregister_all(dev);
> > > diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> > > index 5762a7c441e9..718c7f961d8a 100644
> > > --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> > > +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> > > @@ -181,7 +181,7 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct drm_device *dev,
> > >   	fb_helper = &fbdev_cma->fb_helper;
> > > -	ret = drm_client_new(dev, &fb_helper->client, "fbdev");
> > > +	ret = drm_client_new(dev, &fb_helper->client, "fbdev", NULL);
> > >   	if (ret)
> > >   		goto err_free;
> > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > > index 0a0a577ebc3c..bea3a0cb324a 100644
> > > --- a/drivers/gpu/drm/drm_fb_helper.c
> > > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > > @@ -2989,8 +2989,15 @@ static void drm_fbdev_fb_destroy(struct fb_info *info)
> > >   	}
> > >   	drm_client_framebuffer_delete(fb_helper->buffer);
> > > -	drm_client_release(&fb_helper->client);
> > > -	kfree(fb_helper);
> > > +	/*
> > > +	 * FIXME:
> > > +	 * Remove conditional when all CMA drivers have been moved over to using
> > > +	 * drm_fbdev_generic_setup().
> > > +	 */
> > > +	if (fb_helper->client.funcs) {
> > > +		drm_client_release(&fb_helper->client);
> > > +		kfree(fb_helper);
> > > +	}
> > >   }
> > >   static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
> > > diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> > > index 66bb403dc8ab..ffa8dc35515f 100644
> > > --- a/drivers/gpu/drm/drm_file.c
> > > +++ b/drivers/gpu/drm/drm_file.c
> > > @@ -35,6 +35,7 @@
> > >   #include <linux/slab.h>
> > >   #include <linux/module.h>
> > > +#include <drm/drm_client.h>
> > >   #include <drm/drm_file.h>
> > >   #include <drm/drmP.h>
> > > @@ -444,6 +445,8 @@ void drm_lastclose(struct drm_device * dev)
> > >   	if (drm_core_check_feature(dev, DRIVER_LEGACY))
> > >   		drm_legacy_dev_reinit(dev);
> > > +
> > > +	drm_client_dev_restore(dev);
> > >   }
> > >   /**
> > > diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> > > index 527743394150..26be57e28a9d 100644
> > > --- a/drivers/gpu/drm/drm_probe_helper.c
> > > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > > @@ -33,6 +33,7 @@
> > >   #include <linux/moduleparam.h>
> > >   #include <drm/drmP.h>
> > > +#include <drm/drm_client.h>
> > >   #include <drm/drm_crtc.h>
> > >   #include <drm/drm_fourcc.h>
> > >   #include <drm/drm_crtc_helper.h>
> > > @@ -563,6 +564,8 @@ void drm_kms_helper_hotplug_event(struct drm_device *dev)
> > >   	drm_sysfs_hotplug_event(dev);
> > >   	if (dev->mode_config.funcs->output_poll_changed)
> > >   		dev->mode_config.funcs->output_poll_changed(dev);
> > > +
> > > +	drm_client_dev_hotplug(dev);
> > >   }
> > >   EXPORT_SYMBOL(drm_kms_helper_hotplug_event);
> > > diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
> > > index e366f95d4414..02cbb02714d8 100644
> > > --- a/include/drm/drm_client.h
> > > +++ b/include/drm/drm_client.h
> > > @@ -5,10 +5,66 @@
> > >   #include <linux/types.h>
> > > +struct drm_client_dev;
> > >   struct drm_device;
> > >   struct drm_file;
> > >   struct drm_framebuffer;
> > >   struct drm_gem_object;
> > > +struct module;
> > > +
> > > +/**
> > > + * struct drm_client_funcs - DRM client callbacks
> > > + */
> > > +struct drm_client_funcs {
> > > +	/**
> > > +	 * @owner: The module owner
> > > +	 */
> > > +	struct module *owner;
> > > +
> > > +	/**
> > > +	 * @release:
> > > +	 *
> > > +	 * Called when the reference count is dropped to zero. Users of this
> > > +	 * callback is responsible for calling drm_client_close() and freeing
> > > +	 * the client structure.
> > > +	 *
> > > +	 * This callback is optional.
> > > +	 */
> > > +	void (*release)(struct drm_client_dev *client);
> > Hm, is this no longer in use?
> > 
> > > +
> > > +	/**
> > > +	 * @unregister:
> > > +	 *
> > > +	 * Called when &drm_device is unregistered. The client should respond by
> > > +	 * releasing it's resources using drm_client_put(). If it can't do so
> > > +	 * due to resoruces being tied up, like fbdev with open file handles,
> > > +	 * it should release it's resources as soon as possible.
> > This still talks about refcounting and _put ... needs a refresher.
> > 
> > > +	 *
> > > +	 * This callback is optional.
> > > +	 */
> > > +	void (*unregister)(struct drm_client_dev *client);
> > > +
> > > +	/**
> > > +	 * @restore:
> > > +	 *
> > > +	 * Called on drm_lastclose(). The first client instance in the list that
> > > +	 * returns zero gets the privilege to restore and no more clients are
> > > +	 * called. This callback is not called after @unregister has been called.
> > > +	 *
> > > +	 * This callback is optional.
> > > +	 */
> > > +	int (*restore)(struct drm_client_dev *client);
> > > +
> > > +	/**
> > > +	 * @hotplug:
> > > +	 *
> > > +	 * Called on drm_kms_helper_hotplug_event().
> > > +	 * This callback is not called after @unregister has been called.
> > > +	 *
> > > +	 * This callback is optional.
> > > +	 */
> > > +	int (*hotplug)(struct drm_client_dev *client);
> > > +};
> > >   /**
> > >    * struct drm_client_dev - DRM client instance
> > > @@ -24,6 +80,19 @@ struct drm_client_dev {
> > >   	 */
> > >   	const char *name;
> > > +	/**
> > > +	 * @list:
> > > +	 *
> > > +	 * List of all clients of a DRM device, linked into
> > > +	 * &drm_device.clientlist. Protected by &drm_device.clientlist_mutex.
> > > +	 */
> > > +	struct list_head list;
> > > +
> > > +	/**
> > > +	 * @funcs: DRM client functions (optional)
> > > +	 */
> > > +	const struct drm_client_funcs *funcs;
> > > +
> > >   	/**
> > >   	 * @file: DRM file
> > >   	 */
> > > @@ -31,9 +100,13 @@ struct drm_client_dev {
> > >   };
> > >   int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
> > > -		   const char *name);
> > > +		   const char *name, const struct drm_client_funcs *funcs);
> > >   void drm_client_release(struct drm_client_dev *client);
> > > +void drm_client_dev_unregister(struct drm_device *dev);
> > > +void drm_client_dev_hotplug(struct drm_device *dev);
> > > +void drm_client_dev_restore(struct drm_device *dev);
> > > +
> > >   /**
> > >    * struct drm_client_buffer - DRM client buffer
> > >    */
> > > diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> > > index 9e29976d4e98..f9c6e0e3aec7 100644
> > > --- a/include/drm/drm_device.h
> > > +++ b/include/drm/drm_device.h
> > > @@ -81,6 +81,20 @@ struct drm_device {
> > >   	 */
> > >   	struct list_head filelist_internal;
> > > +	/**
> > > +	 * @clientlist_mutex:
> > > +	 *
> > > +	 * Protects @clientlist access.
> > > +	 */
> > > +	struct mutex clientlist_mutex;
> > > +
> > > +	/**
> > > +	 * @clientlist:
> > > +	 *
> > > +	 * List of in-kernel clients. Protected by @clientlist_mutex.
> > > +	 */
> > > +	struct list_head clientlist;
> > > +
> > >   	/** \name Memory management */
> > >   	/*@{ */
> > >   	struct list_head maplist;	/**< Linked list of regions */
> > > -- 
> > > 2.15.1
> > > 
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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