[Intel-gfx] [RFC PATCH 2/2] drm/i915/display: Implement fb_mmap callback function

[Das, Nirmoy]

Ping, please provide some feedback on this.

On 3/7/2023 3:46 PM, Nirmoy Das wrote:
> If stolen memory allocation fails for fbdev, the driver will
> fallback to system memory. Calculation of smem_start is wrong
> for such framebuffer objs if the platform comes with no gmadr or
> no aperture. Solve this by adding fb_mmap callback which will
> use GTT if aperture is available otherwise will use cpu to access
> the framebuffer.
>
> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_fbdev.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
> index 3659350061a7..67427d020bd3 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> @@ -40,8 +40,10 @@
>   #include <drm/drm_crtc.h>
>   #include <drm/drm_fb_helper.h>
>   #include <drm/drm_fourcc.h>
> +#include <drm/drm_gem_framebuffer_helper.h>
>   
>   #include "gem/i915_gem_lmem.h"
> +#include "gem/i915_gem_mman.h"
>   
>   #include "i915_drv.h"
>   #include "intel_display_types.h"
> @@ -120,6 +122,16 @@ static int intel_fbdev_pan_display(struct fb_var_screeninfo *var,
>   	return ret;
>   }
>   
> +#define to_intel_fbdev(x) container_of(x, struct intel_fbdev, helper)
> +static int intel_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma)
> +{
> +	struct intel_fbdev *fbdev = to_intel_fbdev(info->par);
> +	struct drm_gem_object *bo = drm_gem_fb_get_obj(&fbdev->fb->base, 0);
> +	struct drm_i915_gem_object *obj = to_intel_bo(bo);
> +
> +	return i915_gem_fb_mmap(obj, vma);
> +}
> +
>   static const struct fb_ops intelfb_ops = {
>   	.owner = THIS_MODULE,
>   	DRM_FB_HELPER_DEFAULT_OPS,
> @@ -131,6 +143,7 @@ static const struct fb_ops intelfb_ops = {
>   	.fb_imageblit = drm_fb_helper_cfb_imageblit,
>   	.fb_pan_display = intel_fbdev_pan_display,
>   	.fb_blank = intel_fbdev_blank,
> +	.fb_mmap = intel_fbdev_mmap,
>   };
>   
>   static int intelfb_alloc(struct drm_fb_helper *helper,