Re: [PATCH] vboxvideo: Fix incorrect type in assignment sparse warning

[Hans de Goede]

Hi,

On 06-01-18 15:20, Alexander Kapshuk wrote:
> On Mon, Dec 25, 2017 at 04:42:59PM +0200, Alexander Kapshuk wrote:
> > Sparse emitted the following warning:
> > ../drivers/staging/vboxvideo/vbox_fb.c:173:27: warning: incorrect type in assignment (different address spaces)
> > ../drivers/staging/vboxvideo/vbox_fb.c:173:27:    expected char [noderef] <asn:2>*screen_base
> > ../drivers/staging/vboxvideo/vbox_fb.c:173:27:    got void *virtual
> >
> > The vbox_bo buffer object kernel mapping is handled by a call
> > to ttm_bo_kmap() prior to the assignment of bo->kmap.virtual to
> > info->screen_base of type char __iomem*.
> > Casting bo->kmap.virtual to char __iomem* in this assignment fixes
> > the warning.
> >
> > vboxvideo: Fix address space of expression removal sparse warning
> >
> > Sparse emitted the following warning:
> > ../drivers/staging/vboxvideo/vbox_main.c:64:25: warning: cast removes address space of expression
> >
> > vbox->vbva_buffers iomapping is handled by calling vbox_accel_init()
> > from vbox_hw_init().
> > __force attribute is used in assignment to vbva to fix the warning.
> >
> > Signed-off-by: Alexander Kapshuk <alexander.kapshuk@xxxxxxxxx>
> > ---
> >   drivers/staging/vboxvideo/vbox_fb.c   | 2 +-
> >   drivers/staging/vboxvideo/vbox_main.c | 2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/vboxvideo/vbox_fb.c b/drivers/staging/vboxvideo/vbox_fb.c
> > index 8aed248db6e2..43c39eca4ae1 100644
> > --- a/drivers/staging/vboxvideo/vbox_fb.c
> > +++ b/drivers/staging/vboxvideo/vbox_fb.c
> > @@ -170,7 +170,7 @@ static int vboxfb_create(struct drm_fb_helper *helper,
> >   	drm_fb_helper_fill_var(info, &fbdev->helper, sizes->fb_width,
> >   			       sizes->fb_height);
> >
> > -	info->screen_base = bo->kmap.virtual;
> > +	info->screen_base = (char __iomem *)bo->kmap.virtual;
> >   	info->screen_size = size;
> >
> >   #ifdef CONFIG_DRM_KMS_FB_HELPER

This fix looks good to me.

> > diff --git a/drivers/staging/vboxvideo/vbox_main.c b/drivers/staging/vboxvideo/vbox_main.c
> > index 80bd039fa08e..973b3bcc04b1 100644
> > --- a/drivers/staging/vboxvideo/vbox_main.c
> > +++ b/drivers/staging/vboxvideo/vbox_main.c
> > @@ -61,7 +61,7 @@ void vbox_enable_accel(struct vbox_private *vbox)
> >   		if (vbox->vbva_info[i].vbva)
> >   			continue;
> >
> > -		vbva = (void *)vbox->vbva_buffers + i * VBVA_MIN_BUFFER_SIZE;
> > +		vbva = (void __force *)vbox->vbva_buffers + i * VBVA_MIN_BUFFER_SIZE;
> >   		if (!vbva_enable(&vbox->vbva_info[i],
> >   				 vbox->guest_pool, vbva, i)) {
> >   			/* very old host or driver error. */

Hmm, isn't there a cleaner way to fix this ? Maybe make vbva_enable's
argument (and the local vbva variable) of type u8 __iomem * too ?

Regards,

Hans