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From: "Noralf Trønnes" <noralf@tronnes.org>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: Re: [RFC v4 21/25] drm/fb-helper: Add drm_fb_helper_fb_open/release()
Date: Mon, 16 Apr 2018 18:10:07 +0200	[thread overview]
Message-ID: <e1305f94-8fb1-2baa-6507-848c90b96036@tronnes.org> (raw)
In-Reply-To: <20180416084644.GP31310@phenom.ffwll.local>


Den 16.04.2018 10.46, skrev Daniel Vetter:
> On Sat, Apr 14, 2018 at 01:53:14PM +0200, Noralf Trønnes wrote:
>> These helpers keep track of fbdev users and drm_driver.last_close will
>> only restore fbdev when actually in use. Additionally the display is
>> turned off when the last user is closing. fbcon is a user in this context.
>>
>> If struct fb_ops is defined in a library, fb_open() takes a ref on the
>> library (fb_ops.owner) instead of the driver module. Fix that by ensuring
>> that the driver module is pinned.
>>
>> The functions are not added to the DRM_FB_HELPER_DEFAULT_OPS() macro,
>> because some of its users do set fb_open/release themselves.
>>
>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
>> ---
>>   drivers/gpu/drm/drm_fb_helper.c | 54 ++++++++++++++++++++++++++++++++++++++++-
>>   include/drm/drm_fb_helper.h     | 29 ++++++++++++++++++++++
>>   2 files changed, 82 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 98e5bc92c9f2..b1124c08b1ed 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -177,7 +177,7 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
>>   	if (!drm_fbdev_emulation || !fb_helper)
>>   		return -ENODEV;
>>   
>> -	if (READ_ONCE(fb_helper->deferred_setup))
>> +	if (READ_ONCE(fb_helper->deferred_setup) || !READ_ONCE(fb_helper->open_count))
>>   		return 0;
>>   
>>   	mutex_lock(&fb_helper->lock);
>> @@ -368,6 +368,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
>>   	INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
>>   	helper->dirty_clip.x1 = helper->dirty_clip.y1 = ~0;
>>   	mutex_init(&helper->lock);
>> +	helper->open_count = 1;
>>   	helper->funcs = funcs;
>>   	helper->dev = dev;
>>   }
>> @@ -620,6 +621,53 @@ int drm_fb_helper_defio_init(struct drm_fb_helper *fb_helper)
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_defio_init);
>>   
>> +/**
>> + * drm_fb_helper_fb_open - implementation for &fb_ops.fb_open
>> + * @info: fbdev registered by the helper
>> + * @user: 1=userspace, 0=fbcon
>> + *
>> + * Increase fbdev use count.
>> + * If &fb_ops is wrapped in a library, pin the driver module.
>> + */
>> +int drm_fb_helper_fb_open(struct fb_info *info, int user)
>> +{
>> +	struct drm_fb_helper *fb_helper = info->par;
>> +	struct drm_device *dev = fb_helper->dev;
>> +
>> +	if (info->fbops->owner != dev->driver->fops->owner) {
>> +		if (!try_module_get(dev->driver->fops->owner))
>> +			return -ENODEV;
>> +	}
>> +
>> +	fb_helper->open_count++;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL(drm_fb_helper_fb_open);
>> +
>> +/**
>> + * drm_fb_helper_fb_release - implementation for &fb_ops.fb_release
>> + * @info: fbdev registered by the helper
>> + * @user: 1=userspace, 0=fbcon
>> + *
>> + * Decrease fbdev use count and turn off if there are no users left.
>> + * If &fb_ops is wrapped in a library, unpin the driver module.
>> + */
>> +int drm_fb_helper_fb_release(struct fb_info *info, int user)
>> +{
>> +	struct drm_fb_helper *fb_helper = info->par;
>> +	struct drm_device *dev = fb_helper->dev;
>> +
>> +	if (!(--fb_helper->open_count))
>> +		drm_fb_helper_dpms(info, DRM_MODE_DPMS_OFF);
>> +
>> +	if (info->fbops->owner != dev->driver->fops->owner)
>> +		module_put(dev->driver->fops->owner);
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL(drm_fb_helper_fb_release);
>> +
>>   /**
>>    * drm_fb_helper_sys_read - wrapper around fb_sys_read
>>    * @info: fb_info struct pointer
>> @@ -1436,6 +1484,10 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
>>   	if (ret < 0)
>>   		return ret;
>>   
>> +	/* Block restore without users if we do track it */
>> +	if (fb_helper->fbdev->fbops->fb_open == drm_fb_helper_fb_open)
>> +		fb_helper->open_count = 0;
> Since we kzcalloc, isn't this entirely redundant? Looks confusing to me at
> least.

I have to keep the existing restore behaviour for those that don't use
drm_fb_helper_fb_open(). I do this by setting fb_helper->open_count = 1
in drm_fb_helper_prepare(). I have tried to give a describtion in the
@open_count docs.

Ofc I could have changed all drivers to use drm_fb_helper_fb_open(), but
I think that time is better spent moving drivers over to generic fbdev
instead.

Noralf.

> Otherwise looks all reasonable.
> -Daniel
>
>
>> +
>>   	strcpy(fb_helper->fb->comm, "[fbcon]");
>>   	return 0;
>>   }
>> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
>> index 5f66f253a97b..330983975d5e 100644
>> --- a/include/drm/drm_fb_helper.h
>> +++ b/include/drm/drm_fb_helper.h
>> @@ -184,6 +184,22 @@ struct drm_fb_helper {
>>   	 * See also: @deferred_setup
>>   	 */
>>   	int preferred_bpp;
>> +
>> +	/**
>> +	 * @open_count:
>> +	 *
>> +	 * Keeps track of fbdev use to know when to not restore fbdev and to
>> +	 * disable the pipeline when the last user is gone.
>> +	 *
>> +	 * Drivers that use drm_fb_helper_fb_open() as their \.fb_open
>> +	 * callback will get an initial value of 0 and get restore based on
>> +	 * actual use. Others will get an initial value of 1 which means that
>> +	 * fbdev will always be restored. Drivers that call
>> +	 * drm_fb_helper_fb_open() in their \.fb_open, thus needs to set the
>> +	 * initial value to 0 themselves in their &drm_fb_helper_funcs->fb_probe
>> +	 * callback.
>> +	 */
>> +	unsigned int open_count;
>>   };
>>   
>>   /**
>> @@ -230,6 +246,9 @@ void drm_fb_helper_deferred_io(struct fb_info *info,
>>   			       struct list_head *pagelist);
>>   int drm_fb_helper_defio_init(struct drm_fb_helper *fb_helper);
>>   
>> +int drm_fb_helper_fb_open(struct fb_info *info, int user);
>> +int drm_fb_helper_fb_release(struct fb_info *info, int user);
>> +
>>   ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
>>   			       size_t count, loff_t *ppos);
>>   ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
>> @@ -376,6 +395,16 @@ static inline int drm_fb_helper_defio_init(struct drm_fb_helper *fb_helper)
>>   	return -ENODEV;
>>   }
>>   
>> +static inline int drm_fb_helper_fb_open(struct fb_info *info, int user)
>> +{
>> +	return -ENODEV;
>> +}
>> +
>> +static inline int drm_fb_helper_fb_release(struct fb_info *info, int user)
>> +{
>> +	return -ENODEV;
>> +}
>> +
>>   static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
>>   					     char __user *buf, size_t count,
>>   					     loff_t *ppos)
>> -- 
>> 2.15.1
>>
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

_______________________________________________
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  reply	other threads:[~2018-04-16 16:10 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-14 11:52 [RFC v4 00/25] drm: Add generic fbdev emulation Noralf Trønnes
2018-04-14 11:52 ` [RFC v4 01/25] drm: provide management functions for drm_file Noralf Trønnes
2018-04-14 11:52 ` [RFC v4 02/25] drm/file: Don't set master on in-kernel clients Noralf Trønnes
2018-04-14 11:52 ` [RFC v4 03/25] drm/fb-helper: No need to cache rotation and sw_rotations Noralf Trønnes
2018-04-14 11:52 ` [RFC v4 04/25] drm/fb-helper: Remove drm_fb_helper_debug_enter/leave() Noralf Trønnes
2018-04-14 11:52 ` [RFC v4 05/25] drm/fb-helper: dpms_legacy(): Only set on connectors in use Noralf Trønnes
2018-04-14 11:52 ` [RFC v4 06/25] drm/atomic: Move __drm_atomic_helper_disable_plane/set_config() Noralf Trønnes
2018-04-16  8:30   ` Daniel Vetter
2018-04-14 11:53 ` [RFC v4 07/25] drm: Begin an API for in-kernel clients Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 08/25] drm/fb-helper: Use struct drm_client_display Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 09/25] drm/fb-helper: Move modeset commit code to drm_client Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 10/25] drm/connector: Add drm_connector_has_preferred_mode/pick_cmdline_mode() Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 11/25] drm/connector: Add connector array functions Noralf Trønnes
2018-04-16  8:33   ` Daniel Vetter
2018-04-14 11:53 ` [RFC v4 12/25] drm/i915: Add drm_driver->initial_client_display callback Noralf Trønnes
2018-04-16  8:38   ` Daniel Vetter
2019-03-01 11:46     ` [Intel-gfx] " Noralf Trønnes
2019-03-01 11:51       ` Daniel Vetter
2018-04-14 11:53 ` [RFC v4 13/25] drm/fb-helper: Remove struct drm_fb_helper_crtc Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 14/25] drm/fb-helper: Remove struct drm_fb_helper_connector Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 15/25] drm/fb-helper: Move modeset config code to drm_client Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 16/25] drm: Make ioctls available for in-kernel clients Noralf Trønnes
2018-04-16  9:04   ` Daniel Vetter
2018-04-14 11:53 ` [RFC v4 17/25] drm/client: Bail out if there's a DRM master Noralf Trønnes
2018-04-16  8:45   ` Daniel Vetter
2018-04-14 11:53 ` [RFC v4 18/25] drm/client: Make the display modes available to clients Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 19/25] drm/client: Finish the in-kernel client API Noralf Trønnes
2018-04-16  8:27   ` [Intel-gfx] " Daniel Vetter
2018-04-16 15:58     ` Noralf Trønnes
2018-04-17  8:08       ` Daniel Vetter
2018-04-14 11:53 ` [RFC v4 20/25] drm/prime: Don't pin module on export for in-kernel clients Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 21/25] drm/fb-helper: Add drm_fb_helper_fb_open/release() Noralf Trønnes
2018-04-16  8:46   ` Daniel Vetter
2018-04-16 16:10     ` Noralf Trønnes [this message]
2018-04-17  8:14       ` [Intel-gfx] " Daniel Vetter
2018-04-14 11:53 ` [RFC v4 22/25] drm/fb-helper: Add generic fbdev emulation Noralf Trønnes
2018-04-16  8:52   ` Daniel Vetter
2018-04-14 11:53 ` [RFC v4 23/25] drm: Add DRM device registered notifier Noralf Trønnes
2018-04-17 10:16   ` Daniel Vetter
2018-04-14 11:53 ` [RFC v4 24/25] drm/client: Hack: Add bootsplash Noralf Trønnes
2018-04-14 11:53 ` [RFC v4 25/25] drm/client: Hack: Add DRM VT console client Noralf Trønnes
2018-04-16  8:21 ` [RFC v4 00/25] drm: Add generic fbdev emulation Daniel Vetter
2018-04-16 18:49   ` Noralf Trønnes
2018-04-17  8:10     ` [Intel-gfx] " Daniel Vetter
  -- strict thread matches above, loose matches on Subject: below --
2018-04-13 16:53 Noralf Trønnes
2018-04-13 16:53 ` [RFC v4 21/25] drm/fb-helper: Add drm_fb_helper_fb_open/release() Noralf Trønnes
2018-04-12 16:12 [RFC v4 12/25] drm/i915: Add drm_driver->initial_client_display callback Noralf Trønnes
2018-04-12 16:12 ` [RFC v4 21/25] drm/fb-helper: Add drm_fb_helper_fb_open/release() Noralf Trønnes

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