Incorporate Linux-compatible data structures for the framebuffer's `ioctl`

kernel/src/device/fb.rs

@@ -30,6 +30,177 @@ struct FbHandle {
     framebuffer: Arc<FrameBuffer>,
 }
 
+/// Bitfields describing the color channel layout; `struct fb_bitfield` in Linux.
+///
+/// Reference: <https://elixir.bootlin.com/linux/v6.17/source/include/uapi/linux/fb.h#L189>.
+#[repr(C)]
+#[derive(Debug, Clone, Copy, Pod, Default)]
+struct FbBitfield {
+    /// Bit offset of the field
+    pub offset: u32,
+    /// Length of the field in bits
+    pub length: u32,
+    /// Most significant bit position (0 = left, 1 = right)
+    pub msb_right: u32,
+}
+
+impl FbBitfield {
+    /// Converts pixel format to framebuffer bitfields for Linux compatibility.
+    #[rustfmt::skip]
+    fn from_pixel_format(pixel_format: PixelFormat) -> (Self, Self, Self, Self) {
+        match pixel_format {
+            PixelFormat::Grayscale8 => (
+                Self { offset: 0, length: 8, msb_right: 0 },
+                Self { offset: 0, length: 8, msb_right: 0 },
+                Self { offset: 0, length: 8, msb_right: 0 },
+                Self::default(),
+            ),
+            PixelFormat::Rgb565 => (
+                Self { offset: 11, length: 5, msb_right: 0 },
+                Self { offset: 5, length: 6, msb_right: 0 },
+                Self { offset: 0, length: 5, msb_right: 0 },
+                Self::default(),
+            ),
+            PixelFormat::Rgb888 => (
+                Self { offset: 16, length: 8, msb_right: 0 },
+                Self { offset: 8, length: 8, msb_right: 0 },
+                Self { offset: 0, length: 8, msb_right: 0 },
+                Self::default(),
+            ),
+            PixelFormat::BgrReserved => (
+                Self { offset: 16, length: 8, msb_right: 0 },
+                Self { offset: 8, length: 8, msb_right: 0 },
+                Self { offset: 0, length: 8, msb_right: 0 },
+                Self { offset: 24, length: 8, msb_right: 0 },
+            ),
+        }
+    }
+}
+
+/// Variable screen information for framebuffer devices; `struct fb_var_screeninfo` in Linux.
+///
+/// Reference: <https://elixir.bootlin.com/linux/v6.17/source/include/uapi/linux/fb.h#L243>.
+#[repr(C)]
+#[derive(Debug, Default, Clone, Copy, Pod)]
+struct FbVarScreenInfo {
+    /// Visible resolution width
+    pub xres: u32,
+    /// Visible resolution height
+    pub yres: u32,
+    /// Virtual resolution width
+    pub xres_virtual: u32,
+    /// Virtual resolution height
+    pub yres_virtual: u32,
+    /// Offset from virtual to visible (horizontal)
+    pub xoffset: u32,
+    /// Offset from virtual to visible (vertical)
+    pub yoffset: u32,
+    /// Color depth in bits per pixel
+    pub bits_per_pixel: u32,
+    /// 0 = color, 1 = grayscale, >1 = FOURCC
+    pub grayscale: u32,
+    /// Red color bitfield in framebuffer memory
+    pub red: FbBitfield,
+    /// Green color bitfield in framebuffer memory
+    pub green: FbBitfield,
+    /// Blue color bitfield in framebuffer memory
+    pub blue: FbBitfield,
+    /// Transparency bitfield
+    pub transp: FbBitfield,
+    /// Non-standard pixel format indicator
+    pub nonstd: u32,
+    /// Activation control flags
+    pub activate: u32,
+    /// Height of display in millimeters
+    pub height: u32,
+    /// Width of display in millimeters
+    pub width: u32,
+    /// Acceleration capabilities (obsolete)
+    pub accel_flags: u32,
+    /// Pixel clock period in picoseconds
+    pub pixclock: u32,
+    /// Time from horizontal sync to picture
+    pub left_margin: u32,
+    /// Time from picture to horizontal sync
+    pub right_margin: u32,
+    /// Time from vertical sync to picture
+    pub upper_margin: u32,
+    /// Time from picture to vertical sync
+    pub lower_margin: u32,
+    /// Length of horizontal sync
+    pub hsync_len: u32,
+    /// Length of vertical sync
+    pub vsync_len: u32,
+    /// Synchronization flags
+    pub sync: u32,
+    /// Video mode flags
+    pub vmode: u32,
+    /// Screen rotation angle (counter-clockwise)
+    pub rotate: u32,
+    /// Colorspace for FOURCC-based modes
+    pub colorspace: u32,
+    /// Reserved for future compatibility
+    pub reserved: [u32; 4],
+}
+
+/// Fixed screen information for framebuffer devices; `struct fb_fix_screeninfo` in Linux.
+///
+/// Reference: <https://elixir.bootlin.com/linux/v6.17/source/include/uapi/linux/fb.h#L158>.
+#[repr(C)]
+#[derive(Debug, Default, Clone, Copy, Pod)]
+struct FbFixScreenInfo {
+    /// Identification string (e.g., "EFI VGA")
+    pub id: [u8; 16],
+    /// Start of framebuffer memory (physical address)
+    pub smem_start: u64,
+    /// Length of framebuffer memory in bytes
+    pub smem_len: u32,
+    /// Framebuffer type identifier
+    pub type_: u32,
+    /// Auxiliary type information (e.g., interleave)
+    pub type_aux: u32,
+    /// Visual type (mono, pseudo-color, true-color, etc.)
+    pub visual: u32,
+    /// Horizontal panning step size (0 = no panning)
+    pub xpanstep: u16,
+    /// Vertical panning step size (0 = no panning)
+    pub ypanstep: u16,
+    /// Y-axis wrapping step size (0 = no wrapping)
+    pub ywrapstep: u16,
+    /// Length of a screen line in bytes
+    pub line_length: u32,
+    /// Start of memory-mapped I/O (physical address)
+    pub mmio_start: u64,
+    /// Length of memory-mapped I/O region
+    pub mmio_len: u32,
+    /// Hardware acceleration type identifier
+    pub accel: u32,
+    /// Hardware capability flags
+    pub capabilities: u16,
+    /// Reserved for future compatibility
+    pub reserved: [u16; 2],
+}
+
+/// Framebuffer colormap structure for userspace communication.
+///
+/// Reference: <https://elixir.bootlin.com/linux/v6.17/source/include/uapi/linux/fb.h#L283>.
+#[repr(C)]
+#[derive(Debug, Clone, Copy, Pod)]
+struct FbCmapUser {
+    /// Starting offset in colormap
+    pub start: u32,
+    /// Number of colormap entries
+    pub len: u32,
+    /// Pointer to red color values in userspace
+    pub red: usize,
+    /// Pointer to green color values in userspace
+    pub green: usize,
+    /// Pointer to blue color values in userspace
+    pub blue: usize,
+    /// Pointer to transparency values in userspace (may be null)
+    pub transp: usize,
+}
+
 impl CharDevice for Fb {
     fn devtmpfs_name(&self) -> DevtmpfsName<'_> {
         DevtmpfsName::new("fb0", None)