Re: [Intel-gfx] [PATCH 1/2] video/fb: Propagate error code from failing to unregister conflicting fb

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 16 Dec 2013, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> If we fail to remove a conflicting fb driver, we need to abort the
> loading of the second driver to avoid likely kernel panics.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
> Cc: linux-fbdev@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> ---
>  drivers/video/fbmem.c | 31 +++++++++++++++++++++----------
>  include/linux/fb.h    |  4 ++--
>  2 files changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
> index 010d19105ebc..e296967a3abb 100644
> --- a/drivers/video/fbmem.c
> +++ b/drivers/video/fbmem.c
> @@ -1577,10 +1577,10 @@ static bool fb_do_apertures_overlap(struct apertures_struct *gena,
>  static int do_unregister_framebuffer(struct fb_info *fb_info);
>  
>  #define VGA_FB_PHYS 0xA0000
> -static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
> -				     const char *name, bool primary)
> +static int do_remove_conflicting_framebuffers(struct apertures_struct *a,
> +					      const char *name, bool primary)
>  {
> -	int i;
> +	int i, ret;
>  
>  	/* check all firmware fbs and kick off if the base addr overlaps */
>  	for (i = 0 ; i < FB_MAX; i++) {
> @@ -1599,22 +1599,29 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
>  			printk(KERN_INFO "fb: conflicting fb hw usage "
>  			       "%s vs %s - removing generic driver\n",
>  			       name, registered_fb[i]->fix.id);
> -			do_unregister_framebuffer(registered_fb[i]);
> +			ret = do_unregister_framebuffer(registered_fb[i]);
> +			if (ret)
> +				return ret;

An observation, this bails out early instead of trying to unregister all
the conflicting framebuffers regardless of errors like before. We're
probably doomed either way?

Reviewed-by: Jani Nikula <jani.nikula@intel.com>



>  		}
>  	}
> +
> +	return 0;
>  }
>  
>  static int do_register_framebuffer(struct fb_info *fb_info)
>  {
> -	int i;
> +	int i, ret;
>  	struct fb_event event;
>  	struct fb_videomode mode;
>  
>  	if (fb_check_foreignness(fb_info))
>  		return -ENOSYS;
>  
> -	do_remove_conflicting_framebuffers(fb_info->apertures, fb_info->fix.id,
> -					 fb_is_primary_device(fb_info));
> +	ret = do_remove_conflicting_framebuffers(fb_info->apertures,
> +						 fb_info->fix.id,
> +						 fb_is_primary_device(fb_info));
> +	if (ret)
> +		return ret;
>  
>  	if (num_registered_fb = FB_MAX)
>  		return -ENXIO;
> @@ -1739,12 +1746,16 @@ int unlink_framebuffer(struct fb_info *fb_info)
>  }
>  EXPORT_SYMBOL(unlink_framebuffer);
>  
> -void remove_conflicting_framebuffers(struct apertures_struct *a,
> -				     const char *name, bool primary)
> +int remove_conflicting_framebuffers(struct apertures_struct *a,
> +				    const char *name, bool primary)
>  {
> +	int ret;
> +
>  	mutex_lock(&registration_lock);
> -	do_remove_conflicting_framebuffers(a, name, primary);
> +	ret = do_remove_conflicting_framebuffers(a, name, primary);
>  	mutex_unlock(&registration_lock);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(remove_conflicting_framebuffers);
>  
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 70c4836e4a9f..fe6ac956550e 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -613,8 +613,8 @@ extern ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
>  extern int register_framebuffer(struct fb_info *fb_info);
>  extern int unregister_framebuffer(struct fb_info *fb_info);
>  extern int unlink_framebuffer(struct fb_info *fb_info);
> -extern void remove_conflicting_framebuffers(struct apertures_struct *a,
> -				const char *name, bool primary);
> +extern int remove_conflicting_framebuffers(struct apertures_struct *a,
> +					   const char *name, bool primary);
>  extern int fb_prepare_logo(struct fb_info *fb_info, int rotate);
>  extern int fb_show_logo(struct fb_info *fb_info, int rotate);
>  extern char* fb_get_buffer_offset(struct fb_info *info, struct fb_pixmap *buf, u32 size);
> -- 
> 1.8.5.1
>
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-- 
Jani Nikula, Intel Open Source Technology Center