drivers/gpu/drm/udl/udl_transfer.c

Source file repositories/reference/linux-study-clean/drivers/gpu/drm/udl/udl_transfer.c

File Facts

System
Linux kernel
Corpus path
drivers/gpu/drm/udl/udl_transfer.c
Extension
.c
Size
6697 bytes
Lines
218
Domain
Driver Families
Bucket
drivers/gpu
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

while (pixel < cmd_pixel_end) {
			const u8 *const start = pixel;
			const uint16_t repeating_pixel_val16 = pixel_val16;

			put_unaligned_be16(pixel_val16, cmd);

			cmd += 2;
			pixel += bpp;

			while (pixel < cmd_pixel_end) {
				pixel_val16 = get_pixel_val16(pixel, log_bpp);
				if (pixel_val16 != repeating_pixel_val16)
					break;
				pixel += bpp;
			}

			if (unlikely(pixel > start + bpp)) {
				/* go back and fill in raw pixel count */
				*raw_pixels_count_byte = (((start -
						raw_pixel_start) >> log_bpp) + 1) & 0xFF;

				/* immediately after raw data is repeat byte */
				*cmd++ = (((pixel - start) >> log_bpp) - 1) & 0xFF;

				/* Then start another raw pixel span */
				raw_pixel_start = pixel;
				raw_pixels_count_byte = cmd++;
			}
		}

		if (pixel > raw_pixel_start) {
			/* finalize last RAW span */
			*raw_pixels_count_byte = ((pixel - raw_pixel_start) >> log_bpp) & 0xFF;
		} else {
			/* undo unused byte */
			cmd--;
		}

		*cmd_pixels_count_byte = ((pixel - cmd_pixel_start) >> log_bpp) & 0xFF;
		dev_addr += ((pixel - cmd_pixel_start) >> log_bpp) * 2;
	}

	if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
		/* Fill leftover bytes with no-ops */
		if (cmd_buffer_end > cmd)
			memset(cmd, UDL_MSG_BULK, cmd_buffer_end - cmd);
		cmd = (uint8_t *) cmd_buffer_end;
	}

	*command_buffer_ptr = cmd;
	*pixel_start_ptr = pixel;
	*device_address_ptr = dev_addr;

	return;
}

/*
 * There are 3 copies of every pixel: The front buffer that the fbdev
 * client renders to, the actual framebuffer across the USB bus in hardware
 * (that we can only write to, slowly, and can never read), and (optionally)
 * our shadow copy that tracks what's been sent to that hardware buffer.
 */
int udl_render_hline(struct udl_device *udl, int log_bpp, struct urb **urb_ptr,
		     const char *front, char **urb_buf_ptr,
		     u32 byte_offset, u32 device_byte_offset,
		     u32 byte_width)
{
	const u8 *line_start, *line_end, *next_pixel;
	u32 base16 = 0 + (device_byte_offset >> log_bpp) * 2;
	struct urb *urb = *urb_ptr;
	u8 *cmd = *urb_buf_ptr;
	u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;

	if (WARN_ON(!(log_bpp == 1 || log_bpp == 2))) {
		/* need to finish URB at error from this function */
		udl_urb_completion(urb);
		return -EINVAL;
	}

	line_start = (u8 *) (front + byte_offset);
	next_pixel = line_start;
	line_end = next_pixel + byte_width;

	while (next_pixel < line_end) {

		udl_compress_hline16(&next_pixel,
			     line_end, &base16,
			     (u8 **) &cmd, (u8 *) cmd_end, log_bpp);

		if (cmd >= cmd_end) {

Annotation

Implementation Notes