[PATCH] fbdev: Introduce devm_register_framebuffer()

[Thomas Weißschuh]

Introduce a device-managed variant of register_framebuffer() which
automatically unregisters the framebuffer on device destruction.
This can simplify the error handling and resource management in drivers.

Signed-off-by: Thomas Weißschuh <linux at weissschuh.net>
---
This is a fixed resend of [0], which was broken.
Thanks to Bert [1], and Chaitanya Kumar [2]
for reporting the issue.

[0] https://lore.kernel.org/lkml/20240827-efifb-sysfs-v1-3-c9cc3e052180@weissschuh.net/
[1] https://lore.kernel.org/lkml/20240829224124.2978-1-spasswolf@web.de/
[2] https://lore.kernel.org/lkml/SJ1PR11MB612925C1C533C09F8F62F7CBB9972@SJ1PR11MB6129.namprd11.prod.outlook.com/

Helge, I didn't document the function devm_unregister_framebuffer() as
it is only an internal helper and will ever only used by one user,
similar to other helpers in fbmem.c.
---
 drivers/video/fbdev/core/fbmem.c | 30 ++++++++++++++++++++++++++++++
 include/linux/fb.h               |  1 +
 2 files changed, 31 insertions(+)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 4c4ad0a86a50..3c568cff2913 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -544,6 +544,36 @@ unregister_framebuffer(struct fb_info *fb_info)
 }
 EXPORT_SYMBOL(unregister_framebuffer);
 
+static void devm_unregister_framebuffer(void *data)
+{
+	struct fb_info *info = data;
+
+	unregister_framebuffer(info);
+}
+
+/**
+ *	devm_register_framebuffer - resource-managed frame buffer device registration
+ *	@dev: device the framebuffer belongs to
+ *	@fb_info: frame buffer info structure
+ *
+ *	Registers a frame buffer device @fb_info to device @dev.
+ *
+ *	Returns negative errno on error, or zero for success.
+ *
+ */
+int
+devm_register_framebuffer(struct device *dev, struct fb_info *fb_info)
+{
+	int ret;
+
+	ret = register_framebuffer(fb_info);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev, devm_unregister_framebuffer, fb_info);
+}
+EXPORT_SYMBOL(devm_register_framebuffer);
+
 /**
  *	fb_set_suspend - low level driver signals suspend
  *	@info: framebuffer affected
diff --git a/include/linux/fb.h b/include/linux/fb.h
index db7d97b10964..abf6643ebcaf 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -601,6 +601,7 @@ extern ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
 /* fbmem.c */
 extern int register_framebuffer(struct fb_info *fb_info);
 extern void unregister_framebuffer(struct fb_info *fb_info);
+extern int devm_register_framebuffer(struct device *dev, struct fb_info *fb_info);
 extern char* fb_get_buffer_offset(struct fb_info *info, struct fb_pixmap *buf, u32 size);
 extern void fb_pad_unaligned_buffer(u8 *dst, u32 d_pitch, u8 *src, u32 idx,
 				u32 height, u32 shift_high, u32 shift_low, u32 mod);

---
base-commit: 20371ba120635d9ab7fc7670497105af8f33eb08
change-id: 20240830-fbdev-devm_register_framebuffer-647e9c103b9a

Best regards,
-- 
Thomas Weißschuh <linux at weissschuh.net>