[media] usbtv: improve a comment

[cascardo/linux.git] / drivers / media / usb / usbtv / usbtv-video.c

diff --git a/drivers/media/usb/usbtv/usbtv-video.c b/drivers/media/usb/usbtv/usbtv-video.c
index f6cfad4..2a08975 100644 (file)
--- a/drivers/media/usb/usbtv/usbtv-video.c
+++ b/drivers/media/usb/usbtv/usbtv-video.c
@@ -1,19 +1,6 @@
 /*
- * Fushicai USBTV007 Audio-Video Grabber Driver
- *
- * Product web site:
- * http://www.fushicai.com/products_detail/&productId=d05449ee-b690-42f9-a661-aa7353894bed.html
- *
- * Following LWN articles were very useful in construction of this driver:
- * Video4Linux2 API series: http://lwn.net/Articles/203924/
- * videobuf2 API explanation: http://lwn.net/Articles/447435/
- * Thanks go to Jonathan Corbet for providing this quality documentation.
- * He is awesome.
- *
  * Copyright (c) 2013 Lubomir Rintel
  * All rights reserved.
- * No physical hardware was harmed running Windows during the
- * reverse-engineering activity
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -26,6 +13,33 @@
  *
  * Alternatively, this software may be distributed under the terms of the
  * GNU General Public License ("GPL").
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+/*
+ * Fushicai USBTV007 Audio-Video Grabber Driver
+ *
+ * Product web site:
+ * http://www.fushicai.com/products_detail/&productId=d05449ee-b690-42f9-a661-aa7353894bed.html
+ *
+ * Following LWN articles were very useful in construction of this driver:
+ * Video4Linux2 API series: http://lwn.net/Articles/203924/
+ * videobuf2 API explanation: http://lwn.net/Articles/447435/
+ * Thanks go to Jonathan Corbet for providing this quality documentation.
+ * He is awesome.
+ *
+ * No physical hardware was harmed running Windows during the
+ * reverse-engineering activity
  */
 
 #include <media/v4l2-ioctl.h>
@@ -251,8 +265,23 @@ static int usbtv_setup_capture(struct usbtv *usbtv)
 /* Copy data from chunk into a frame buffer, deinterlacing the data
  * into every second line. Unfortunately, they don't align nicely into
  * 720 pixel lines, as the chunk is 240 words long, which is 480 pixels.
- * Therefore, we break down the chunk into two halves before copyting,
- * so that we can interleave a line if needed. */
+ * Therefore, we break down the chunk into two halves before copying,
+ * so that we can interleave a line if needed.
+ *
+ * Each "chunk" is 240 words; a word in this context equals 4 bytes.
+ * Image format is YUYV/YUV 4:2:2, consisting of Y Cr Y Cb, defining two
+ * pixels, the Cr and Cb shared between the two pixels, but each having
+ * separate Y values. Thus, the 240 words equal 480 pixels. It therefore,
+ * takes 1.5 chunks to make a 720 pixel-wide line for the frame.
+ * The image is interlaced, so there is a "scan" of odd lines, followed
+ * by "scan" of even numbered lines.
+ *
+ * Following code is writing the chunks in correct sequence, skipping
+ * the rows based on "odd" value.
+ * line 1: chunk[0][  0..479] chunk[0][480..959] chunk[1][  0..479]
+ * line 3: chunk[1][480..959] chunk[2][  0..479] chunk[2][480..959]
+ * ...etc.
+ */
 static void usbtv_chunk_to_vbuf(u32 *frame, __be32 *src, int chunk_no, int odd)
 {
        int half;
@@ -608,7 +637,7 @@ static struct v4l2_file_operations usbtv_fops = {
 
 static int usbtv_queue_setup(struct vb2_queue *vq,
        unsigned int *nbuffers,
-       unsigned int *nplanes, unsigned int sizes[], void *alloc_ctxs[])
+       unsigned int *nplanes, unsigned int sizes[], struct device *alloc_devs[])
 {
        struct usbtv *usbtv = vb2_get_drv_priv(vq);
        unsigned size = USBTV_CHUNK * usbtv->n_chunks * 2 * sizeof(u32);