[v2] drm: fb-helper: Reject all pixel format changing requests

Message ID 20181003164538.5534-1-Eugeniy.Paltsev@synopsys.com
State New
Headers show
Series
  • [v2] drm: fb-helper: Reject all pixel format changing requests
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Commit Message

Eugeniy Paltsev Oct. 3, 2018, 4:45 p.m.
drm fbdev emulation doesn't support changing the pixel format at all,
so reject all pixel format changing requests.

Cc: stable@vger.kernel.org
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
Changes v1->v2:
 * Reject all pixel format changing request, not just the invalid ones.

 drivers/gpu/drm/drm_fb_helper.c | 91 ++++++++++++-----------------------------
 1 file changed, 26 insertions(+), 65 deletions(-)

Comments

Daniel Vetter Oct. 4, 2018, 7:56 a.m. | #1
On Wed, Oct 03, 2018 at 07:45:38PM +0300, Eugeniy Paltsev wrote:
> drm fbdev emulation doesn't support changing the pixel format at all,
> so reject all pixel format changing requests.

For next time around: Please keep the note here why we need this and what
the impact is. Otherwise it's not immediately clear why we should backport
this patch to all stable kernels.

I'll gather a few acks and then apply.
-Daniel
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> ---
> Changes v1->v2:
>  * Reject all pixel format changing request, not just the invalid ones.
> 
>  drivers/gpu/drm/drm_fb_helper.c | 91 ++++++++++++-----------------------------
>  1 file changed, 26 insertions(+), 65 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 16ec93b75dbf..48598d7f673f 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1580,6 +1580,25 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
>  }
>  EXPORT_SYMBOL(drm_fb_helper_ioctl);
>  
> +static bool drm_fb_pixel_format_equal(const struct fb_var_screeninfo *var_1,
> +				      const struct fb_var_screeninfo *var_2)
> +{
> +	return var_1->bits_per_pixel == var_2->bits_per_pixel &&
> +	       var_1->grayscale == var_2->grayscale &&
> +	       var_1->red.offset == var_2->red.offset &&
> +	       var_1->red.length == var_2->red.length &&
> +	       var_1->red.msb_right == var_2->red.msb_right &&
> +	       var_1->green.offset == var_2->green.offset &&
> +	       var_1->green.length == var_2->green.length &&
> +	       var_1->green.msb_right == var_2->green.msb_right &&
> +	       var_1->blue.offset == var_2->blue.offset &&
> +	       var_1->blue.length == var_2->blue.length &&
> +	       var_1->blue.msb_right == var_2->blue.msb_right &&
> +	       var_1->transp.offset == var_2->transp.offset &&
> +	       var_1->transp.length == var_2->transp.length &&
> +	       var_1->transp.msb_right == var_2->transp.msb_right;
> +}
> +
>  /**
>   * drm_fb_helper_check_var - implementation for &fb_ops.fb_check_var
>   * @var: screeninfo to check
> @@ -1590,7 +1609,6 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>  {
>  	struct drm_fb_helper *fb_helper = info->par;
>  	struct drm_framebuffer *fb = fb_helper->fb;
> -	int depth;
>  
>  	if (var->pixclock != 0 || in_dbg_master())
>  		return -EINVAL;
> @@ -1610,72 +1628,15 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>  		return -EINVAL;
>  	}
>  
> -	switch (var->bits_per_pixel) {
> -	case 16:
> -		depth = (var->green.length == 6) ? 16 : 15;
> -		break;
> -	case 32:
> -		depth = (var->transp.length > 0) ? 32 : 24;
> -		break;
> -	default:
> -		depth = var->bits_per_pixel;
> -		break;
> -	}
> -
> -	switch (depth) {
> -	case 8:
> -		var->red.offset = 0;
> -		var->green.offset = 0;
> -		var->blue.offset = 0;
> -		var->red.length = 8;
> -		var->green.length = 8;
> -		var->blue.length = 8;
> -		var->transp.length = 0;
> -		var->transp.offset = 0;
> -		break;
> -	case 15:
> -		var->red.offset = 10;
> -		var->green.offset = 5;
> -		var->blue.offset = 0;
> -		var->red.length = 5;
> -		var->green.length = 5;
> -		var->blue.length = 5;
> -		var->transp.length = 1;
> -		var->transp.offset = 15;
> -		break;
> -	case 16:
> -		var->red.offset = 11;
> -		var->green.offset = 5;
> -		var->blue.offset = 0;
> -		var->red.length = 5;
> -		var->green.length = 6;
> -		var->blue.length = 5;
> -		var->transp.length = 0;
> -		var->transp.offset = 0;
> -		break;
> -	case 24:
> -		var->red.offset = 16;
> -		var->green.offset = 8;
> -		var->blue.offset = 0;
> -		var->red.length = 8;
> -		var->green.length = 8;
> -		var->blue.length = 8;
> -		var->transp.length = 0;
> -		var->transp.offset = 0;
> -		break;
> -	case 32:
> -		var->red.offset = 16;
> -		var->green.offset = 8;
> -		var->blue.offset = 0;
> -		var->red.length = 8;
> -		var->green.length = 8;
> -		var->blue.length = 8;
> -		var->transp.length = 8;
> -		var->transp.offset = 24;
> -		break;
> -	default:
> +	/*
> +	 * drm fbdev emulation doesn't support changing the pixel format at all,
> +	 * so reject all pixel format changing requests.
> +	 */
> +	if (!drm_fb_pixel_format_equal(var, &info->var)) {
> +		DRM_DEBUG("fbdev emulation doesn't support changing the pixel format\n");
>  		return -EINVAL;
>  	}
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL(drm_fb_helper_check_var);
> -- 
> 2.14.4
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
Ville Syrjälä Oct. 4, 2018, 10:34 a.m. | #2
On Wed, Oct 03, 2018 at 07:45:38PM +0300, Eugeniy Paltsev wrote:
> drm fbdev emulation doesn't support changing the pixel format at all,
> so reject all pixel format changing requests.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> ---
> Changes v1->v2:
>  * Reject all pixel format changing request, not just the invalid ones.
> 
>  drivers/gpu/drm/drm_fb_helper.c | 91 ++++++++++++-----------------------------
>  1 file changed, 26 insertions(+), 65 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 16ec93b75dbf..48598d7f673f 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1580,6 +1580,25 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
>  }
>  EXPORT_SYMBOL(drm_fb_helper_ioctl);
>  
> +static bool drm_fb_pixel_format_equal(const struct fb_var_screeninfo *var_1,
> +				      const struct fb_var_screeninfo *var_2)
> +{
> +	return var_1->bits_per_pixel == var_2->bits_per_pixel &&
> +	       var_1->grayscale == var_2->grayscale &&
> +	       var_1->red.offset == var_2->red.offset &&
> +	       var_1->red.length == var_2->red.length &&
> +	       var_1->red.msb_right == var_2->red.msb_right &&
> +	       var_1->green.offset == var_2->green.offset &&
> +	       var_1->green.length == var_2->green.length &&
> +	       var_1->green.msb_right == var_2->green.msb_right &&
> +	       var_1->blue.offset == var_2->blue.offset &&
> +	       var_1->blue.length == var_2->blue.length &&
> +	       var_1->blue.msb_right == var_2->blue.msb_right &&
> +	       var_1->transp.offset == var_2->transp.offset &&
> +	       var_1->transp.length == var_2->transp.length &&
> +	       var_1->transp.msb_right == var_2->transp.msb_right;
> +}

Could have shortened a bit with memcmp() but this works too.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

I suppose we really should be doing the same for most of the rest of
var_screeninfo as we don't allow changing the timings/etc. either.

> +
>  /**
>   * drm_fb_helper_check_var - implementation for &fb_ops.fb_check_var
>   * @var: screeninfo to check
> @@ -1590,7 +1609,6 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>  {
>  	struct drm_fb_helper *fb_helper = info->par;
>  	struct drm_framebuffer *fb = fb_helper->fb;
> -	int depth;
>  
>  	if (var->pixclock != 0 || in_dbg_master())
>  		return -EINVAL;
> @@ -1610,72 +1628,15 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>  		return -EINVAL;
>  	}
>  
> -	switch (var->bits_per_pixel) {
> -	case 16:
> -		depth = (var->green.length == 6) ? 16 : 15;
> -		break;
> -	case 32:
> -		depth = (var->transp.length > 0) ? 32 : 24;
> -		break;
> -	default:
> -		depth = var->bits_per_pixel;
> -		break;
> -	}
> -
> -	switch (depth) {
> -	case 8:
> -		var->red.offset = 0;
> -		var->green.offset = 0;
> -		var->blue.offset = 0;
> -		var->red.length = 8;
> -		var->green.length = 8;
> -		var->blue.length = 8;
> -		var->transp.length = 0;
> -		var->transp.offset = 0;
> -		break;
> -	case 15:
> -		var->red.offset = 10;
> -		var->green.offset = 5;
> -		var->blue.offset = 0;
> -		var->red.length = 5;
> -		var->green.length = 5;
> -		var->blue.length = 5;
> -		var->transp.length = 1;
> -		var->transp.offset = 15;
> -		break;
> -	case 16:
> -		var->red.offset = 11;
> -		var->green.offset = 5;
> -		var->blue.offset = 0;
> -		var->red.length = 5;
> -		var->green.length = 6;
> -		var->blue.length = 5;
> -		var->transp.length = 0;
> -		var->transp.offset = 0;
> -		break;
> -	case 24:
> -		var->red.offset = 16;
> -		var->green.offset = 8;
> -		var->blue.offset = 0;
> -		var->red.length = 8;
> -		var->green.length = 8;
> -		var->blue.length = 8;
> -		var->transp.length = 0;
> -		var->transp.offset = 0;
> -		break;
> -	case 32:
> -		var->red.offset = 16;
> -		var->green.offset = 8;
> -		var->blue.offset = 0;
> -		var->red.length = 8;
> -		var->green.length = 8;
> -		var->blue.length = 8;
> -		var->transp.length = 8;
> -		var->transp.offset = 24;
> -		break;
> -	default:
> +	/*
> +	 * drm fbdev emulation doesn't support changing the pixel format at all,
> +	 * so reject all pixel format changing requests.
> +	 */
> +	if (!drm_fb_pixel_format_equal(var, &info->var)) {
> +		DRM_DEBUG("fbdev emulation doesn't support changing the pixel format\n");
>  		return -EINVAL;
>  	}
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL(drm_fb_helper_check_var);
> -- 
> 2.14.4
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
Daniel Vetter Oct. 4, 2018, 10:49 a.m. | #3
On Thu, Oct 04, 2018 at 01:34:22PM +0300, Ville Syrjälä wrote:
> On Wed, Oct 03, 2018 at 07:45:38PM +0300, Eugeniy Paltsev wrote:
> > drm fbdev emulation doesn't support changing the pixel format at all,
> > so reject all pixel format changing requests.
> > 
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> > ---
> > Changes v1->v2:
> >  * Reject all pixel format changing request, not just the invalid ones.
> > 
> >  drivers/gpu/drm/drm_fb_helper.c | 91 ++++++++++++-----------------------------
> >  1 file changed, 26 insertions(+), 65 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > index 16ec93b75dbf..48598d7f673f 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -1580,6 +1580,25 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
> >  }
> >  EXPORT_SYMBOL(drm_fb_helper_ioctl);
> >  
> > +static bool drm_fb_pixel_format_equal(const struct fb_var_screeninfo *var_1,
> > +				      const struct fb_var_screeninfo *var_2)
> > +{
> > +	return var_1->bits_per_pixel == var_2->bits_per_pixel &&
> > +	       var_1->grayscale == var_2->grayscale &&
> > +	       var_1->red.offset == var_2->red.offset &&
> > +	       var_1->red.length == var_2->red.length &&
> > +	       var_1->red.msb_right == var_2->red.msb_right &&
> > +	       var_1->green.offset == var_2->green.offset &&
> > +	       var_1->green.length == var_2->green.length &&
> > +	       var_1->green.msb_right == var_2->green.msb_right &&
> > +	       var_1->blue.offset == var_2->blue.offset &&
> > +	       var_1->blue.length == var_2->blue.length &&
> > +	       var_1->blue.msb_right == var_2->blue.msb_right &&
> > +	       var_1->transp.offset == var_2->transp.offset &&
> > +	       var_1->transp.length == var_2->transp.length &&
> > +	       var_1->transp.msb_right == var_2->transp.msb_right;
> > +}
> 
> Could have shortened a bit with memcmp() but this works too.

I'm always vary of memcmp with structs that might have padding and stuff.

> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> I suppose we really should be doing the same for most of the rest of
> var_screeninfo as we don't allow changing the timings/etc. either.

Timing at least doens't have an immediate correctness impact of userspace
rendering the wrong format :-)

Thanks for review&patch, applied to drm-misc-fixes.
-Daniel

> 
> > +
> >  /**
> >   * drm_fb_helper_check_var - implementation for &fb_ops.fb_check_var
> >   * @var: screeninfo to check
> > @@ -1590,7 +1609,6 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> >  {
> >  	struct drm_fb_helper *fb_helper = info->par;
> >  	struct drm_framebuffer *fb = fb_helper->fb;
> > -	int depth;
> >  
> >  	if (var->pixclock != 0 || in_dbg_master())
> >  		return -EINVAL;
> > @@ -1610,72 +1628,15 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> >  		return -EINVAL;
> >  	}
> >  
> > -	switch (var->bits_per_pixel) {
> > -	case 16:
> > -		depth = (var->green.length == 6) ? 16 : 15;
> > -		break;
> > -	case 32:
> > -		depth = (var->transp.length > 0) ? 32 : 24;
> > -		break;
> > -	default:
> > -		depth = var->bits_per_pixel;
> > -		break;
> > -	}
> > -
> > -	switch (depth) {
> > -	case 8:
> > -		var->red.offset = 0;
> > -		var->green.offset = 0;
> > -		var->blue.offset = 0;
> > -		var->red.length = 8;
> > -		var->green.length = 8;
> > -		var->blue.length = 8;
> > -		var->transp.length = 0;
> > -		var->transp.offset = 0;
> > -		break;
> > -	case 15:
> > -		var->red.offset = 10;
> > -		var->green.offset = 5;
> > -		var->blue.offset = 0;
> > -		var->red.length = 5;
> > -		var->green.length = 5;
> > -		var->blue.length = 5;
> > -		var->transp.length = 1;
> > -		var->transp.offset = 15;
> > -		break;
> > -	case 16:
> > -		var->red.offset = 11;
> > -		var->green.offset = 5;
> > -		var->blue.offset = 0;
> > -		var->red.length = 5;
> > -		var->green.length = 6;
> > -		var->blue.length = 5;
> > -		var->transp.length = 0;
> > -		var->transp.offset = 0;
> > -		break;
> > -	case 24:
> > -		var->red.offset = 16;
> > -		var->green.offset = 8;
> > -		var->blue.offset = 0;
> > -		var->red.length = 8;
> > -		var->green.length = 8;
> > -		var->blue.length = 8;
> > -		var->transp.length = 0;
> > -		var->transp.offset = 0;
> > -		break;
> > -	case 32:
> > -		var->red.offset = 16;
> > -		var->green.offset = 8;
> > -		var->blue.offset = 0;
> > -		var->red.length = 8;
> > -		var->green.length = 8;
> > -		var->blue.length = 8;
> > -		var->transp.length = 8;
> > -		var->transp.offset = 24;
> > -		break;
> > -	default:
> > +	/*
> > +	 * drm fbdev emulation doesn't support changing the pixel format at all,
> > +	 * so reject all pixel format changing requests.
> > +	 */
> > +	if (!drm_fb_pixel_format_equal(var, &info->var)) {
> > +		DRM_DEBUG("fbdev emulation doesn't support changing the pixel format\n");
> >  		return -EINVAL;
> >  	}
> > +
> >  	return 0;
> >  }
> >  EXPORT_SYMBOL(drm_fb_helper_check_var);
> > -- 
> > 2.14.4
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Ville Syrjälä
> Intel
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
Ville Syrjälä Oct. 4, 2018, 11 a.m. | #4
On Thu, Oct 04, 2018 at 12:49:38PM +0200, Daniel Vetter wrote:
> On Thu, Oct 04, 2018 at 01:34:22PM +0300, Ville Syrjälä wrote:
> > On Wed, Oct 03, 2018 at 07:45:38PM +0300, Eugeniy Paltsev wrote:
> > > drm fbdev emulation doesn't support changing the pixel format at all,
> > > so reject all pixel format changing requests.
> > > 
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> > > ---
> > > Changes v1->v2:
> > >  * Reject all pixel format changing request, not just the invalid ones.
> > > 
> > >  drivers/gpu/drm/drm_fb_helper.c | 91 ++++++++++++-----------------------------
> > >  1 file changed, 26 insertions(+), 65 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > > index 16ec93b75dbf..48598d7f673f 100644
> > > --- a/drivers/gpu/drm/drm_fb_helper.c
> > > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > > @@ -1580,6 +1580,25 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
> > >  }
> > >  EXPORT_SYMBOL(drm_fb_helper_ioctl);
> > >  
> > > +static bool drm_fb_pixel_format_equal(const struct fb_var_screeninfo *var_1,
> > > +				      const struct fb_var_screeninfo *var_2)
> > > +{
> > > +	return var_1->bits_per_pixel == var_2->bits_per_pixel &&
> > > +	       var_1->grayscale == var_2->grayscale &&
> > > +	       var_1->red.offset == var_2->red.offset &&
> > > +	       var_1->red.length == var_2->red.length &&
> > > +	       var_1->red.msb_right == var_2->red.msb_right &&
> > > +	       var_1->green.offset == var_2->green.offset &&
> > > +	       var_1->green.length == var_2->green.length &&
> > > +	       var_1->green.msb_right == var_2->green.msb_right &&
> > > +	       var_1->blue.offset == var_2->blue.offset &&
> > > +	       var_1->blue.length == var_2->blue.length &&
> > > +	       var_1->blue.msb_right == var_2->blue.msb_right &&
> > > +	       var_1->transp.offset == var_2->transp.offset &&
> > > +	       var_1->transp.length == var_2->transp.length &&
> > > +	       var_1->transp.msb_right == var_2->transp.msb_right;
> > > +}
> > 
> > Could have shortened a bit with memcmp() but this works too.
> 
> I'm always vary of memcmp with structs that might have padding and stuff.

These are uabi so padding would be rather bad.

> 
> > Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > I suppose we really should be doing the same for most of the rest of
> > var_screeninfo as we don't allow changing the timings/etc. either.
> 
> Timing at least doens't have an immediate correctness impact of userspace
> rendering the wrong format :-)
> 
> Thanks for review&patch, applied to drm-misc-fixes.
> -Daniel
> 
> > 
> > > +
> > >  /**
> > >   * drm_fb_helper_check_var - implementation for &fb_ops.fb_check_var
> > >   * @var: screeninfo to check
> > > @@ -1590,7 +1609,6 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> > >  {
> > >  	struct drm_fb_helper *fb_helper = info->par;
> > >  	struct drm_framebuffer *fb = fb_helper->fb;
> > > -	int depth;
> > >  
> > >  	if (var->pixclock != 0 || in_dbg_master())
> > >  		return -EINVAL;
> > > @@ -1610,72 +1628,15 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> > >  		return -EINVAL;
> > >  	}
> > >  
> > > -	switch (var->bits_per_pixel) {
> > > -	case 16:
> > > -		depth = (var->green.length == 6) ? 16 : 15;
> > > -		break;
> > > -	case 32:
> > > -		depth = (var->transp.length > 0) ? 32 : 24;
> > > -		break;
> > > -	default:
> > > -		depth = var->bits_per_pixel;
> > > -		break;
> > > -	}
> > > -
> > > -	switch (depth) {
> > > -	case 8:
> > > -		var->red.offset = 0;
> > > -		var->green.offset = 0;
> > > -		var->blue.offset = 0;
> > > -		var->red.length = 8;
> > > -		var->green.length = 8;
> > > -		var->blue.length = 8;
> > > -		var->transp.length = 0;
> > > -		var->transp.offset = 0;
> > > -		break;
> > > -	case 15:
> > > -		var->red.offset = 10;
> > > -		var->green.offset = 5;
> > > -		var->blue.offset = 0;
> > > -		var->red.length = 5;
> > > -		var->green.length = 5;
> > > -		var->blue.length = 5;
> > > -		var->transp.length = 1;
> > > -		var->transp.offset = 15;
> > > -		break;
> > > -	case 16:
> > > -		var->red.offset = 11;
> > > -		var->green.offset = 5;
> > > -		var->blue.offset = 0;
> > > -		var->red.length = 5;
> > > -		var->green.length = 6;
> > > -		var->blue.length = 5;
> > > -		var->transp.length = 0;
> > > -		var->transp.offset = 0;
> > > -		break;
> > > -	case 24:
> > > -		var->red.offset = 16;
> > > -		var->green.offset = 8;
> > > -		var->blue.offset = 0;
> > > -		var->red.length = 8;
> > > -		var->green.length = 8;
> > > -		var->blue.length = 8;
> > > -		var->transp.length = 0;
> > > -		var->transp.offset = 0;
> > > -		break;
> > > -	case 32:
> > > -		var->red.offset = 16;
> > > -		var->green.offset = 8;
> > > -		var->blue.offset = 0;
> > > -		var->red.length = 8;
> > > -		var->green.length = 8;
> > > -		var->blue.length = 8;
> > > -		var->transp.length = 8;
> > > -		var->transp.offset = 24;
> > > -		break;
> > > -	default:
> > > +	/*
> > > +	 * drm fbdev emulation doesn't support changing the pixel format at all,
> > > +	 * so reject all pixel format changing requests.
> > > +	 */
> > > +	if (!drm_fb_pixel_format_equal(var, &info->var)) {
> > > +		DRM_DEBUG("fbdev emulation doesn't support changing the pixel format\n");
> > >  		return -EINVAL;
> > >  	}
> > > +
> > >  	return 0;
> > >  }
> > >  EXPORT_SYMBOL(drm_fb_helper_check_var);
> > > -- 
> > > 2.14.4
> > > 
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > 
> > -- 
> > Ville Syrjälä
> > Intel
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

Patch

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 16ec93b75dbf..48598d7f673f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1580,6 +1580,25 @@  int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
 }
 EXPORT_SYMBOL(drm_fb_helper_ioctl);
 
+static bool drm_fb_pixel_format_equal(const struct fb_var_screeninfo *var_1,
+				      const struct fb_var_screeninfo *var_2)
+{
+	return var_1->bits_per_pixel == var_2->bits_per_pixel &&
+	       var_1->grayscale == var_2->grayscale &&
+	       var_1->red.offset == var_2->red.offset &&
+	       var_1->red.length == var_2->red.length &&
+	       var_1->red.msb_right == var_2->red.msb_right &&
+	       var_1->green.offset == var_2->green.offset &&
+	       var_1->green.length == var_2->green.length &&
+	       var_1->green.msb_right == var_2->green.msb_right &&
+	       var_1->blue.offset == var_2->blue.offset &&
+	       var_1->blue.length == var_2->blue.length &&
+	       var_1->blue.msb_right == var_2->blue.msb_right &&
+	       var_1->transp.offset == var_2->transp.offset &&
+	       var_1->transp.length == var_2->transp.length &&
+	       var_1->transp.msb_right == var_2->transp.msb_right;
+}
+
 /**
  * drm_fb_helper_check_var - implementation for &fb_ops.fb_check_var
  * @var: screeninfo to check
@@ -1590,7 +1609,6 @@  int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
 {
 	struct drm_fb_helper *fb_helper = info->par;
 	struct drm_framebuffer *fb = fb_helper->fb;
-	int depth;
 
 	if (var->pixclock != 0 || in_dbg_master())
 		return -EINVAL;
@@ -1610,72 +1628,15 @@  int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
 		return -EINVAL;
 	}
 
-	switch (var->bits_per_pixel) {
-	case 16:
-		depth = (var->green.length == 6) ? 16 : 15;
-		break;
-	case 32:
-		depth = (var->transp.length > 0) ? 32 : 24;
-		break;
-	default:
-		depth = var->bits_per_pixel;
-		break;
-	}
-
-	switch (depth) {
-	case 8:
-		var->red.offset = 0;
-		var->green.offset = 0;
-		var->blue.offset = 0;
-		var->red.length = 8;
-		var->green.length = 8;
-		var->blue.length = 8;
-		var->transp.length = 0;
-		var->transp.offset = 0;
-		break;
-	case 15:
-		var->red.offset = 10;
-		var->green.offset = 5;
-		var->blue.offset = 0;
-		var->red.length = 5;
-		var->green.length = 5;
-		var->blue.length = 5;
-		var->transp.length = 1;
-		var->transp.offset = 15;
-		break;
-	case 16:
-		var->red.offset = 11;
-		var->green.offset = 5;
-		var->blue.offset = 0;
-		var->red.length = 5;
-		var->green.length = 6;
-		var->blue.length = 5;
-		var->transp.length = 0;
-		var->transp.offset = 0;
-		break;
-	case 24:
-		var->red.offset = 16;
-		var->green.offset = 8;
-		var->blue.offset = 0;
-		var->red.length = 8;
-		var->green.length = 8;
-		var->blue.length = 8;
-		var->transp.length = 0;
-		var->transp.offset = 0;
-		break;
-	case 32:
-		var->red.offset = 16;
-		var->green.offset = 8;
-		var->blue.offset = 0;
-		var->red.length = 8;
-		var->green.length = 8;
-		var->blue.length = 8;
-		var->transp.length = 8;
-		var->transp.offset = 24;
-		break;
-	default:
+	/*
+	 * drm fbdev emulation doesn't support changing the pixel format at all,
+	 * so reject all pixel format changing requests.
+	 */
+	if (!drm_fb_pixel_format_equal(var, &info->var)) {
+		DRM_DEBUG("fbdev emulation doesn't support changing the pixel format\n");
 		return -EINVAL;
 	}
+
 	return 0;
 }
 EXPORT_SYMBOL(drm_fb_helper_check_var);