cmdline: parse multiple instances of the vga option

Parse all instances of the vga= option on the command line, in order
to always enforce the last selection on the command line.

Note that it's not safe to parse just the last occurrence of the vga=
option, as then a command line with `vga=current vga=keep` would
result in current being ignored.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/boot/cmdline.c

@@ -277,59 +277,60 @@ static u16 rows2vmode(unsigned int rows)
 
 static void vga_parse(const char *cmdline, early_boot_opts_t *ebo)
 {
-    const char *c;
-    unsigned int tmp, vesa_depth, vesa_height, vesa_width;
-
-    c = find_opt(cmdline, "vga=", true);
-
-    if ( !c )
-        return;
+    const char *c = cmdline;
 
     ebo->boot_vid_mode = ASK_VGA;
 
-    if ( !strmaxcmp(c, "current", delim_chars_comma) )
-        ebo->boot_vid_mode = VIDEO_CURRENT_MODE;
-    else if ( !strsubcmp(c, "text-80x") )
+    while ( (c = find_opt(c, "vga=", true)) != NULL )
     {
-        c += strlen("text-80x");
-        ebo->boot_vid_mode = rows2vmode(strtoui(c, delim_chars_comma, NULL));
-    }
-    else if ( !strsubcmp(c, "gfx-") )
-    {
-        vesa_width = strtoui(c + strlen("gfx-"), "x", &c);
+        unsigned int tmp, vesa_depth, vesa_height, vesa_width;
 
-        if ( vesa_width > U16_MAX )
-            return;
+        if ( !strmaxcmp(c, "current", delim_chars_comma) )
+            ebo->boot_vid_mode = VIDEO_CURRENT_MODE;
+        else if ( !strsubcmp(c, "text-80x") )
+        {
+            c += strlen("text-80x");
+            ebo->boot_vid_mode = rows2vmode(strtoui(c, delim_chars_comma, NULL));
+        }
+        else if ( !strsubcmp(c, "gfx-") )
+        {
+            vesa_width = strtoui(c + strlen("gfx-"), "x", &c);
 
-        /*
-         * Increment c outside of strtoui() because otherwise some
-         * compiler may complain with following message:
-         * warning: operation on 'c' may be undefined.
-         */
-        ++c;
-        vesa_height = strtoui(c, "x", &c);
+            if ( vesa_width > U16_MAX )
+                return;
 
-        if ( vesa_height > U16_MAX )
-            return;
+            /*
+             * Increment c outside of strtoui() because otherwise some
+             * compiler may complain with following message:
+             * warning: operation on 'c' may be undefined.
+             */
+            ++c;
+            vesa_height = strtoui(c, "x", &c);
 
-        vesa_depth = strtoui(++c, delim_chars_comma, NULL);
+            if ( vesa_height > U16_MAX )
+                return;
 
-        if ( vesa_depth > U16_MAX )
-            return;
+            vesa_depth = strtoui(++c, delim_chars_comma, NULL);
 
-        ebo->vesa_width = vesa_width;
-        ebo->vesa_height = vesa_height;
-        ebo->vesa_depth = vesa_depth;
-        ebo->boot_vid_mode = VIDEO_VESA_BY_SIZE;
-    }
-    else if ( !strsubcmp(c, "mode-") )
-    {
-        tmp = strtoui(c + strlen("mode-"), delim_chars_comma, NULL);
+            if ( vesa_depth > U16_MAX )
+                return;
 
-        if ( tmp > U16_MAX )
-            return;
+            ebo->vesa_width = vesa_width;
+            ebo->vesa_height = vesa_height;
+            ebo->vesa_depth = vesa_depth;
+            ebo->boot_vid_mode = VIDEO_VESA_BY_SIZE;
+        }
+        else if ( !strsubcmp(c, "mode-") )
+        {
+            tmp = strtoui(c + strlen("mode-"), delim_chars_comma, NULL);
 
-        ebo->boot_vid_mode = tmp;
+            if ( tmp > U16_MAX )
+                return;
+
+            ebo->boot_vid_mode = tmp;
+        }
+        else if ( !strmaxcmp(c, "ask", delim_chars_comma) )
+            ebo->boot_vid_mode = ASK_VGA;
     }
 }
 #endif