Re: [Xen-devel] [PATCH 3/8] drm/xen-front: fix 32-bit build warning

From: Oleksandr Andrushchenko <andr2000@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>,
	Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
	David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	xen-devel@lists.xen.org,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [Xen-devel] [PATCH 3/8] drm/xen-front: fix 32-bit build warning
Date: Tue, 29 May 2018 08:58:58 +0300	[thread overview]
Message-ID: <d08e0200-f431-8713-0286-cd5bbf3441c8@gmail.com> (raw)
In-Reply-To: <20180525155030.3667352-3-arnd@arndb.de>

Hi,

On 05/25/2018 06:50 PM, Arnd Bergmann wrote:
> In 32-bit kernel builds, we cannot cast between a pointer and a 64-bit
> type:
>
> In file included from drivers/gpu/drm/xen/xen_drm_front_cfg.c:18:
> drivers/gpu/drm/xen/xen_drm_front.h: In function 'xen_drm_front_fb_to_cookie':
> drivers/gpu/drm/xen/xen_drm_front.h:129:9: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    return (u64)fb;
>
> drivers/gpu/drm/xen/xen_drm_front.h: In function 'xen_drm_front_dbuf_to_cookie':
> drivers/gpu/drm/xen/xen_drm_front.h:134:9: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    return (u64)gem_obj;
>
> drivers/gpu/drm/xen/xen_drm_front_shbuf.c: In function 'backend_unmap':
> drivers/gpu/drm/xen/xen_drm_front_shbuf.c:125:4: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>     ((phys_addr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
>
> Using uintptr_t instead probably does what we want here, although it's
> not clear to me why we assign a virtual address pointer to a phys_addr_t
> in backend_unmap().
>
> Fixes: c575b7eeb89f ("drm/xen-front: Add support for Xen PV display frontend")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>   drivers/gpu/drm/xen/xen_drm_front.h       | 4 ++--
>   drivers/gpu/drm/xen/xen_drm_front_shbuf.c | 2 +-
>   2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/xen/xen_drm_front.h b/drivers/gpu/drm/xen/xen_drm_front.h
> index 2c2479b571ae..5693b4a4b02b 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front.h
> +++ b/drivers/gpu/drm/xen/xen_drm_front.h
> @@ -126,12 +126,12 @@ struct xen_drm_front_drm_info {
>   
>   static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
>   {
> -	return (u64)fb;
> +	return (uintptr_t)fb;
>   }
>   
>   static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
>   {
> -	return (u64)gem_obj;
> +	return (uintptr_t)gem_obj;
>   }
>   
>   int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
> diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> index 8099cb343ae3..d333b67cc1a0 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> +++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> @@ -122,7 +122,7 @@ static void guest_calc_num_grefs(struct xen_drm_front_shbuf *buf)
>   }
>   
>   #define xen_page_to_vaddr(page) \
> -		((phys_addr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
> +		((uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
>   
>   static int backend_unmap(struct xen_drm_front_shbuf *buf)
>   {
Thank you for your patch: this issue was already discussed [1] and 
applied [2] to
drm-misc-next.

Thank you,
Oleksandr

[1] https://patchwork.freedesktop.org/patch/224359/
[2] https://patchwork.freedesktop.org/patch/224920/
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