On Fri, Nov 29, 2019 at 12:29:31PM +0200, Jani Nikula wrote:
> 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@xxxxxxxxxxxx>
> Cc: linux-fbdev@xxxxxxxxxxxxxxx
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> ---
> drivers/video/fbdev/core/fb_defio.c | 3 ---
> drivers/video/fbdev/core/fbmem.c | 15 +++++++++++----
> 2 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
> index 82c20c6047b0..a591d291b231 100644
> --- 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 86b06a599f96..990550930a8e 100644
> --- 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);
Oh I function pointer for tidier control flow, neato.
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> 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;
> }
> --
> 2.20.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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