drm/msm: rework GEM_INFO ioctl

Prep work to add a way to get/set the GEM objects debug name.
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_drv.c

@@ -882,21 +882,31 @@ static int msm_ioctl_gem_info(struct drm_device *dev, void *data,
 	struct drm_gem_object *obj;
 	int ret = 0;
 
-	if (args->flags & ~MSM_INFO_FLAGS)
+	if (args->pad)
 		return -EINVAL;
 
+	switch (args->info) {
+	case MSM_INFO_GET_OFFSET:
+	case MSM_INFO_GET_IOVA:
+		/* value returned as immediate, not pointer, so len==0: */
+		if (args->len)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	obj = drm_gem_object_lookup(file, args->handle);
 	if (!obj)
 		return -ENOENT;
 
-	if (args->flags & MSM_INFO_IOVA) {
-		uint64_t iova;
-
-		ret = msm_ioctl_gem_info_iova(dev, obj, &iova);
-		if (!ret)
-			args->offset = iova;
-	} else {
-		args->offset = msm_gem_mmap_offset(obj);
+	switch (args->info) {
+	case MSM_INFO_GET_OFFSET:
+		args->value = msm_gem_mmap_offset(obj);
+		break;
+	case MSM_INFO_GET_IOVA:
+		ret = msm_ioctl_gem_info_iova(dev, obj, &args->value);
+		break;
 	}
 
 	drm_gem_object_put_unlocked(obj);

include/uapi/drm/msm_drm.h

@@ -105,14 +105,22 @@ struct drm_msm_gem_new {
 	__u32 handle;         /* out */
 };
 
-#define MSM_INFO_IOVA	0x01
-
-#define MSM_INFO_FLAGS (MSM_INFO_IOVA)
+/* Get or set GEM buffer info.  The requested value can be passed
+ * directly in 'value', or for data larger than 64b 'value' is a
+ * pointer to userspace buffer, with 'len' specifying the number of
+ * bytes copied into that buffer.  For info returned by pointer,
+ * calling the GEM_INFO ioctl with null 'value' will return the
+ * required buffer size in 'len'
+ */
+#define MSM_INFO_GET_OFFSET	0x00   /* get mmap() offset, returned by value */
+#define MSM_INFO_GET_IOVA	0x01   /* get iova, returned by value */
 
 struct drm_msm_gem_info {
 	__u32 handle;         /* in */
-	__u32 flags;	      /* in - combination of MSM_INFO_* flags */
-	__u64 offset;         /* out, mmap() offset or iova */
+	__u32 info;           /* in - one of MSM_INFO_* */
+	__u64 value;          /* in or out */
+	__u32 len;            /* in or out */
+	__u32 pad;
 };
 
 #define MSM_PREP_READ        0x01