Re: [PATCH 22/30] fbdev/smscufx: Detect registered fb_info from refcount
From: Javier Martinez Canillas <javierm@redhat.com>
Date: 2023-06-07 22:22:51
Also in:
dri-devel, linux-omap, linux-sh, linux-staging
Thomas Zimmermann [off-list ref] writes:
quoted hunk ↗ jump to hunk
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> --- drivers/video/fbdev/smscufx.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/drivers/video/fbdev/smscufx.c b/drivers/video/fbdev/smscufx.c index 17cec62cc65d..adb2b1fe8383 100644 --- 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 */
The struct fb_info .count refcount is protected by the registration_lock mutex in register_framebuffer(). I think this operation isn't thread safe ? But that was also the case for info->dev check, so I guess is OK and this change is for an old fbdev driver anyways. Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> -- Best regards, Javier Martinez Canillas Core Platforms Red Hat