video: fb_defio: preserve user fb_ops

Modifying fb_ops directly to override fb_mmap with fb_deferred_io_mmap
and then resetting it to NULL afterwards causes problems all over the
place. First, it prevents making the fbops member of struct fb_info a
const pointer, which means we can't make struct fb_ops const
anywhere. Second, a few places have to go out of their way to restore
the original fb_mmap pointer that gets reset to NULL.

Since the only user of the fbops->fb_mmap hook is fb_mmap() in fbmem.c,
call fb_deferred_io_mmap() directly when deferred IO is enabled, and
avoid modifying fb_ops altogether.

Simply use info->fbdefio to determine whether deferred IO should be used
or not. This should be accurate enough for all use cases, although
perhaps not pedantically correct.

v2: Simplify considerably by calling fb_deferred_io_mmap() directly
    (Daniel, Ville)

Cc: Jaya Kumar <jayalk@intworks.biz>
Cc: linux-fbdev@vger.kernel.org
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/022c82429da15d6450ff9ac1a897322ec3124db4.1575022735.git.jani.nikula@intel.com

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index 82c20c6047b0e7020c7a678b557e59e488da87dd..a591d291b231af8531174bd7dd8057d767ab13f1 100644 (file)
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -171,7 +171,6 @@ int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
        vma->vm_private_data = info;
        return 0;
 }
-EXPORT_SYMBOL(fb_deferred_io_mmap);
 
 /* workqueue callback */
 static void fb_deferred_io_work(struct work_struct *work)
@@ -206,7 +205,6 @@ void fb_deferred_io_init(struct fb_info *info)
 
        BUG_ON(!fbdefio);
        mutex_init(&fbdefio->lock);
-       info->fbops->fb_mmap = fb_deferred_io_mmap;
        INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
        INIT_LIST_HEAD(&fbdefio->pagelist);
        if (fbdefio->delay == 0) /* set a default of 1 s */
@@ -237,7 +235,6 @@ void fb_deferred_io_cleanup(struct fb_info *info)
                page->mapping = NULL;
        }
 
-       info->fbops->fb_mmap = NULL;
        mutex_destroy(&fbdefio->lock);
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 86b06a599f963668ab1479c8db0cb2688abb6d22..990550930a8e44dde9a6f8379305cc534b6cf455 100644 (file)
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1332,16 +1332,23 @@ static int
 fb_mmap(struct file *file, struct vm_area_struct * vma)
 {
        struct fb_info *info = file_fb_info(file);
-       struct fb_ops *fb;
+       int (*fb_mmap_fn)(struct fb_info *info, struct vm_area_struct *vma);
        unsigned long mmio_pgoff;
        unsigned long start;
        u32 len;
 
        if (!info)
                return -ENODEV;
-       fb = info->fbops;
        mutex_lock(&info->mm_lock);
-       if (fb->fb_mmap) {
+
+       fb_mmap_fn = info->fbops->fb_mmap;
+
+#if IS_ENABLED(CONFIG_FB_DEFERRED_IO)
+       if (info->fbdefio)
+               fb_mmap_fn = fb_deferred_io_mmap;
+#endif
+
+       if (fb_mmap_fn) {
                int res;
 
                /*
@@ -1349,7 +1356,7 @@ fb_mmap(struct file *file, struct vm_area_struct * vma)
                 * SME protection is removed ahead of the call
                 */
                vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
-               res = fb->fb_mmap(info, vma);
+               res = fb_mmap_fn(info, vma);
                mutex_unlock(&info->mm_lock);
                return res;
        }