video: fbdev: vga16fb: fix setting of pixclock because a pass-by-value error

The pixclock is being set locally because it is being passed as a
pass-by-value argument rather than pass-by-reference, so the computed
pixclock is never being set in var->pixclock. Fix this by passing
by reference.

[This dates back to 2002, I found the offending commit from the git
history git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git ]

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jani Nikula <jani.nikula@intel.com>
[b.zolnierkie: minor patch summary fixup]
[b.zolnierkie: removed "Fixes:" tag (not in upstream tree)]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200723170227.996229-1-colin.king@canonical.com

diff --git a/drivers/video/fbdev/vga16fb.c b/drivers/video/fbdev/vga16fb.c
index a20eeb8..52f273a 100644 (file)
--- a/drivers/video/fbdev/vga16fb.c
+++ b/drivers/video/fbdev/vga16fb.c
@@ -243,7 +243,7 @@ static void vga16fb_update_fix(struct fb_info *info)
 }
 
 static void vga16fb_clock_chip(struct vga16fb_par *par,
-                              unsigned int pixclock,
+                              unsigned int *pixclock,
                               const struct fb_info *info,
                               int mul, int div)
 {
@@ -259,14 +259,14 @@ static void vga16fb_clock_chip(struct vga16fb_par *par,
                {     0 /* bad */,    0x00, 0x00}};
        int err;
 
-       pixclock = (pixclock * mul) / div;
+       *pixclock = (*pixclock * mul) / div;
        best = vgaclocks;
-       err = pixclock - best->pixclock;
+       err = *pixclock - best->pixclock;
        if (err < 0) err = -err;
        for (ptr = vgaclocks + 1; ptr->pixclock; ptr++) {
                int tmp;
 
-               tmp = pixclock - ptr->pixclock;
+               tmp = *pixclock - ptr->pixclock;
                if (tmp < 0) tmp = -tmp;
                if (tmp < err) {
                        err = tmp;
@@ -275,7 +275,7 @@ static void vga16fb_clock_chip(struct vga16fb_par *par,
        }
        par->misc |= best->misc;
        par->clkdiv = best->seq_clock_mode;
-       pixclock = (best->pixclock * div) / mul;                
+       *pixclock = (best->pixclock * div) / mul;
 }
                               
 #define FAIL(X) return -EINVAL
@@ -497,10 +497,10 @@ static int vga16fb_check_var(struct fb_var_screeninfo *var,
 
        if (mode & MODE_8BPP)
                /* pixel clock == vga clock / 2 */
-               vga16fb_clock_chip(par, var->pixclock, info, 1, 2);
+               vga16fb_clock_chip(par, &var->pixclock, info, 1, 2);
        else
                /* pixel clock == vga clock */
-               vga16fb_clock_chip(par, var->pixclock, info, 1, 1);
+               vga16fb_clock_chip(par, &var->pixclock, info, 1, 1);
        
        var->red.offset = var->green.offset = var->blue.offset = 
        var->transp.offset = 0;