custom_priv
struct custom_priv *custom_priv;
custom_priv = devm_kzalloc(dev, sizeof(*custom_priv), GFP_KERNEL);
if (!custom_priv)
simple_priv = &custom_priv->simple_priv;
#define simple_to_custom(simple) container_of((simple), struct custom_priv, simple_priv)
struct custom_priv *custom_priv = simple_to_custom(simple_priv);
custom_priv->custom_params = 1;