[PATCH 0/3] Fixes and cleanup for DRM fbdev emulation and deferred I/O

Hello,

This patch series contains two fixes and a cleanup for things that I noticed
while debugging a regression in the fbdev emulation for a DRM driver.

The first two patches are trivial and shoulnd't be controversial, the third
patch is less trivial, but it has been already reviewed by Thomas and I did
test it to make sure that works as expected. With it, I got rid of the WARN
that happened due a mutex used after it has been destroyed.

Best regards,
Javier


Javier Martinez Canillas (3):
  fbdev: Remove unused struct fb_deferred_io .first_io field
  drm/fb-helper: Check fb_deferred_io_init() return value
  drm/fb-helper: Use a per-driver FB deferred I/O handler

 drivers/gpu/drm/drm_fbdev_generic.c | 15 ++++++++-------
 drivers/video/fbdev/core/fb_defio.c |  4 ----
 include/drm/drm_fb_helper.h         | 10 ++++++++++
 include/linux/fb.h                  |  1 -
 4 files changed, 18 insertions(+), 12 deletions(-)

-- 
2.39.0

This optional callback was added in the commit 1f45f9dbb392 ("fb_defio:
add first_io callback") but it was never used by a driver. Let's remove
it since it's unlikely that will be used after a decade that was added.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---

 drivers/video/fbdev/core/fb_defio.c | 4 ----
 include/linux/fb.h                  | 1 -
 2 files changed, 5 deletions(-)

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index c730253ab85c..1b680742b7f3 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c

@@ -157,10 +157,6 @@ static vm_fault_t fb_deferred_io_track_page(struct fb_info *info, unsigned long
 	/* protect against the workqueue changing the page list */
 	mutex_lock(&fbdefio->lock);
 
-	/* first write in this cycle, notify the driver */
-	if (fbdefio->first_io && list_empty(&fbdefio->pagereflist))
-		fbdefio->first_io(info);
-
 	pageref = fb_deferred_io_pageref_get(info, offset, page);
 	if (WARN_ON_ONCE(!pageref)) {
 		ret = VM_FAULT_OOM;

diff --git a/include/linux/fb.h b/include/linux/fb.h
index 30183fd259ae..daf336385613 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h

@@ -215,7 +215,6 @@ struct fb_deferred_io {
 	struct mutex lock; /* mutex that protects the pageref list */
 	struct list_head pagereflist; /* list of pagerefs for touched pages */
 	/* callback */
-	void (*first_io)(struct fb_info *info);
 	void (*deferred_io)(struct fb_info *info, struct list_head *pagelist);
 };
 #endif

-- 
2.39.0

Am 20.01.23 um 13:08 schrieb Javier Martinez Canillas:

This optional callback was added in the commit 1f45f9dbb392 ("fb_defio:
add first_io callback") but it was never used by a driver. Let's remove
it since it's unlikely that will be used after a decade that was added.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

I vaguely remember that this was important at some point. Maybe before 
the big rework of the pagelist? Don't know; it's unused now.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev