refactor(userspace): split syscall/fat16/ext4 by concern; trim comments

crates/drivers/framebuffer/virtio/src/lib.rs

@@ -37,10 +37,8 @@ pub struct VirtioFramebuffer {
 }
 
 impl VirtioFramebuffer {
-    /// Takes over the GPU whose MMIO region `mmio` names: maps it, sets up
-    /// the control queue and command buffer, asks for the display size,
-    /// allocates a framebuffer and makes it the scanout. `None` if it is
-    /// not a virtio GPU or any step fails.
+    /// Takes over the virtio GPU behind `mmio` and makes a framebuffer its
+    /// scanout. `None` if it is not a GPU or any step fails.
     pub fn try_new(mmio: types::bounded::CapSlot) -> Option<Self> {
         libkos::device::map_mmio(mmio, GPU_MMIO_VA).ok()?;
         let regs = GpuMmio;