linux-kernel - [PATCH] drm/fb_helper: Use min_t() to handle size

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Date:   Tue, 10 Nov 2020 10:01:19 +0100
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
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 <geert+renesas@...der.be>
---
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