[Intel-gfx] [RFC v4 21/25] drm/fb-helper: Add drm_fb_helper_fb_open/release()
Noralf Trønnes
noralf at tronnes.org
Mon Apr 16 16:10:07 UTC 2018
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 at 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
>>
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