Re: [Intel-gfx] [RFC v4 21/25] drm/fb-helper: Add drm_fb_helper_fb_open/release()

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.

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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