1. 根目录:
2. drivers
3. media
4. usb
5. pwc
6. pwc-uncompress.c

/* Linux driver for Philips webcam
   Decompression frontend.
   (C) 1999-2003 Nemosoft Unv.
   (C) 2004-2006 Luc Saillard (luc@saillard.org)

   NOTE: this version of pwc is an unofficial (modified) release of pwc & pcwx
   driver and thus may have bugs that are not present in the original version.
   Please send bug reports and support requests to <luc@saillard.org>.
   The decompression routines have been implemented by reverse-engineering the
   Nemosoft binary pwcx module. Caveat emptor.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

   vim: set ts=8:
*/

#include <asm/current.h>
#include <asm/types.h>

#include "pwc.h"
#include "pwc-dec1.h"
#include "pwc-dec23.h"

int pwc_decompress(struct pwc_device *pdev, struct pwc_frame_buf *fbuf)
{
	int n, line, col;
	void *yuv, *image;
	u16 *src;
	u16 *dsty, *dstu, *dstv;

	image = vb2_plane_vaddr(&fbuf->vb, 0);

	yuv = fbuf->data + pdev->frame_header_size;  /* Skip header */

	/* Raw format; that's easy... */
	if (pdev->pixfmt != V4L2_PIX_FMT_YUV420)
	{
		struct pwc_raw_frame *raw_frame = image;
		raw_frame->type = cpu_to_le16(pdev->type);
		raw_frame->vbandlength = cpu_to_le16(pdev->vbandlength);
			/* cmd_buf is always 4 bytes, but sometimes, only the
			 * first 3 bytes is filled (Nala case). We can
			 * determine this using the type of the webcam */
		memcpy(raw_frame->cmd, pdev->cmd_buf, 4);
		memcpy(raw_frame+1, yuv, pdev->frame_size);
		vb2_set_plane_payload(&fbuf->vb, 0,
			pdev->frame_size + sizeof(struct pwc_raw_frame));
		return 0;
	}

	vb2_set_plane_payload(&fbuf->vb, 0,
			      pdev->width * pdev->height * 3 / 2);

	if (pdev->vbandlength == 0) {
		/* Uncompressed mode.
		 *
		 * We do some byte shuffling here to go from the
		 * native format to YUV420P.
		 */
		src = (u16 *)yuv;
		n = pdev->width * pdev->height;
		dsty = (u16 *)(image);
		dstu = (u16 *)(image + n);
		dstv = (u16 *)(image + n + n / 4);

		for (line = 0; line < pdev->height; line++) {
			for (col = 0; col < pdev->width; col += 4) {
				*dsty++ = *src++;
				*dsty++ = *src++;
				if (line & 1)
					*dstv++ = *src++;
				else
					*dstu++ = *src++;
			}
		}

		return 0;
	}

	/*
	 * Compressed;
	 * the decompressor routines will write the data in planar format
	 * immediately.
	 */
	if (DEVICE_USE_CODEC1(pdev->type)) {

		/* TODO & FIXME */
		PWC_ERROR("This chipset is not supported for now\n");
		return -ENXIO; /* No such device or address: missing decompressor */

	} else {
		pwc_dec23_decompress(pdev, yuv, image);
	}
	return 0;
}