2020-11-10 09:03:30

by Geert Uytterhoeven

Subject: [PATCH] drm/fb_helper: Use min_t() to handle size_t and unsigned long

On arm32:

drivers/gpu/drm/drm_fb_helper.c: In function ‘fb_read_screen_base’:
include/linux/minmax.h:18:28: warning: comparison of distinct pointer types lacks a cast
...
drivers/gpu/drm/drm_fb_helper.c:2041:22: note: in expansion of macro ‘min’
2041 | size_t alloc_size = min(count, PAGE_SIZE);
| ^~~
drivers/gpu/drm/drm_fb_helper.c: In function ‘fb_write_screen_base’:
include/linux/minmax.h:18:28: warning: comparison of distinct pointer types lacks a cast
...
drivers/gpu/drm/drm_fb_helper.c:2115:22: note: in expansion of macro ‘min’
2115 | size_t alloc_size = min(count, PAGE_SIZE);
| ^~~

Indeed, on 32-bit size_t is "unsigned int", not "unsigned long".

Fixes: 222ec45f4c69dfa8 ("drm/fb_helper: Support framebuffers in I/O memory")
Signed-off-by: Geert Uytterhoeven <[email protected]>
---
Interestingly, the commit log claims v7 changed:

use min_t(size_t,) (kernel test robot)
---
drivers/gpu/drm/drm_fb_helper.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 01ba1da285116373..25edf670867c6f79 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -2038,7 +2038,7 @@ static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_
loff_t pos)
{
const char __iomem *src = info->screen_base + pos;
- size_t alloc_size = min(count, PAGE_SIZE);
+ size_t alloc_size = min_t(size_t, count, PAGE_SIZE);
ssize_t ret = 0;
int err = 0;
char *tmp;
@@ -2112,7 +2112,7 @@ static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf
loff_t pos)
{
char __iomem *dst = info->screen_base + pos;
- size_t alloc_size = min(count, PAGE_SIZE);
+ size_t alloc_size = min_t(size_t, count, PAGE_SIZE);
ssize_t ret = 0;
int err = 0;
u8 *tmp;
--
2.25.1

2020-11-10 09:21:05

by Thomas Zimmermann

Subject: Re: [PATCH] drm/fb_helper: Use min_t() to handle size_t and unsigned long

Hi

Am 10.11.20 um 10:01 schrieb Geert Uytterhoeven:
> On arm32:
>
> drivers/gpu/drm/drm_fb_helper.c: In function ‘fb_read_screen_base’:
> include/linux/minmax.h:18:28: warning: comparison of distinct pointer types lacks a cast
> ...
> drivers/gpu/drm/drm_fb_helper.c:2041:22: note: in expansion of macro ‘min’
> 2041 | size_t alloc_size = min(count, PAGE_SIZE);
> | ^~~
> drivers/gpu/drm/drm_fb_helper.c: In function ‘fb_write_screen_base’:
> include/linux/minmax.h:18:28: warning: comparison of distinct pointer types lacks a cast
> ...
> drivers/gpu/drm/drm_fb_helper.c:2115:22: note: in expansion of macro ‘min’
> 2115 | size_t alloc_size = min(count, PAGE_SIZE);
> | ^~~
>
> Indeed, on 32-bit size_t is "unsigned int", not "unsigned long".
>
> Fixes: 222ec45f4c69dfa8 ("drm/fb_helper: Support framebuffers in I/O memory")
> Signed-off-by: Geert Uytterhoeven <[email protected]>

Reviewed-by: Thomas Zimmermann <[email protected]>

Thanks a lot. I'll add the patch to drm-misc-next.

> ---
> Interestingly, the commit log claims v7 changed:
>
> use min_t(size_t,) (kernel test robot)

It got fixed in the functions' inner loops, but I missed the other
instances.

Best regards
Thomas

> ---
> drivers/gpu/drm/drm_fb_helper.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 01ba1da285116373..25edf670867c6f79 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -2038,7 +2038,7 @@ static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_
> loff_t pos)
> {
> const char __iomem *src = info->screen_base + pos;
> - size_t alloc_size = min(count, PAGE_SIZE);
> + size_t alloc_size = min_t(size_t, count, PAGE_SIZE);
> ssize_t ret = 0;
> int err = 0;
> char *tmp;
> @@ -2112,7 +2112,7 @@ static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf
> loff_t pos)
> {
> char __iomem *dst = info->screen_base + pos;
> - size_t alloc_size = min(count, PAGE_SIZE);
> + size_t alloc_size = min_t(size_t, count, PAGE_SIZE);
> ssize_t ret = 0;
> int err = 0;
> u8 *tmp;
>

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer