fbdev/smscufx: Detect registered fb_info from refcount

Detect registered instances of fb_info by reading the reference
counter from struct fb_info.read. Avoids looking at the dev field
and prepares fbdev for making struct fb_info.dev optional.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Steve Glendinning <steve.glendinning@shawell.net>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230613110953.24176-31-tzimmermann@suse.de

diff --git a/drivers/video/fbdev/smscufx.c b/drivers/video/fbdev/smscufx.c
index 17cec62cc65db584f97a572281d7003de1090a48..adb2b1fe8383c2c4f105955aa400cda479530b56 100644 (file)
--- a/drivers/video/fbdev/smscufx.c
+++ b/drivers/video/fbdev/smscufx.c
@@ -1496,7 +1496,7 @@ static int ufx_setup_modes(struct ufx_data *dev, struct fb_info *info,
        u8 *edid;
        int i, result = 0, tries = 3;
 
-       if (info->dev) /* only use mutex if info has been registered */
+       if (refcount_read(&info->count)) /* only use mutex if info has been registered */
                mutex_lock(&info->lock);
 
        edid = kmalloc(EDID_LENGTH, GFP_KERNEL);
@@ -1610,7 +1610,7 @@ error:
        if (edid && (dev->edid != edid))
                kfree(edid);
 
-       if (info->dev)
+       if (refcount_read(&info->count))
                mutex_unlock(&info->lock);
 
        return result;