Re: [PATCH] drm/xen-front: fix pointer casts

From: Oleksandr Andrushchenko
Date: Wed May 23 2018 - 05:07:24 EST


On 05/23/2018 12:19 PM, Juergen Gross wrote:
On 21/05/18 09:39, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

Building for a 32-bit target results in warnings from casting
between a 32-bit pointer and a 64-bit integer. Fix the warnings
by casting those pointers to uintptr_t first.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
---
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..8e15dbebc4ba 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 (u64)(uintptr_t)fb;
Do you really still need the cast to u64?
Indeed, I can remove (u64) now, thank you

}
static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
{
- return (u64)gem_obj;
+ return (u64)(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..47fc93847765 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)))
+ ((phys_addr_t)(uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
phys_addr_t for a virtual address?
This is because the resulting value is then passed to gnttab_set_map_op/
gnttab_set_unmap_op which expects host address to be passed as
phys_addr_t addr :(
Please see [1], [2]: regardless of the fact that xen_page_to_vaddr does
produce host address I have to convert it to phys_addr_t then to pass to [1] and [2].
Please also see [3], [4], [5] which either cast to phys_addr_t or
unsigned long or u64.

Juergen

[1] https://elixir.bootlin.com/linux/v4.17-rc6/source/include/xen/grant_table.h#L147
[2] https://elixir.bootlin.com/linux/v4.17-rc6/source/include/xen/grant_table.h#L163
[3] https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/block/xen-blkback/blkback.c#L845
[4] https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/net/xen-netback/netback.c#L334
[5] https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/xen/xenbus/xenbus_client.c#L478