drm/nouveau/bios: check that fixed tvdac gpio data is valid before using it

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/gpu/drm/nouveau/core/subdev/bios/gpio.c b/drivers/gpu/drm/nouveau/core/subdev/bios/gpio.c
index 718267d84c7b..1ae23b328bbd 100644
--- a/drivers/gpu/drm/nouveau/core/subdev/bios/gpio.c
+++ b/drivers/gpu/drm/nouveau/core/subdev/bios/gpio.c
@@ -100,13 +100,17 @@ dcb_gpio_parse(struct nouveau_bios *bios, int idx, u8 func, u8 line,
         /* DCB 2.2, fixed TVDAC GPIO data */
         if ((entry = dcb_table(bios, &ver, &hdr, &cnt, &len)) && ver >= 0x22) {
                 if (func == DCB_GPIO_TVDAC0) {
-                        *gpio = (struct dcb_gpio_func) {
-                                .func = DCB_GPIO_TVDAC0,
-                                .line = nv_ro08(bios, entry - 4) >> 4,
-                                .log[0] = !!(nv_ro08(bios, entry - 5) & 2),
-                                .log[1] =  !(nv_ro08(bios, entry - 5) & 2),
-                        };
-                        return 0;
+                        u8 conf = nv_ro08(bios, entry - 5);
+                        u8 addr = nv_ro08(bios, entry - 4);
+                        if (conf & 0x01) {
+                                *gpio = (struct dcb_gpio_func) {
+                                        .func = DCB_GPIO_TVDAC0,
+                                        .line = addr >> 4,
+                                        .log[0] = !!(conf & 0x02),
+                                        .log[1] =  !(conf & 0x02),
+                                };
+                                return 0;
+                        }
                 }
         }