quoted

+
+struct bcap_format {
+     u8 *desc;
+     u32 pixelformat;
+     enum v4l2_mbus_pixelcode mbus_code;
+     int bpp; /* bytes per pixel */

Don't you think you might have to process 12 bpp formats at some point,
like YUV 4:2:0, or NV12? Maybe better calculate in bits from the beginning?

sounds good, changed in v2

Does it really have to be fixed 32 bits? Seems a plane simple int would do
just fine.

users can't be negative, so I used u32

quoted

+struct bcap_fh {
+     struct v4l2_fh fh;
+     struct bcap_device *bcap_dev;
+     /* indicates whether this file handle is doing IO */
+     u8 io_allowed;

bool

does kernel prefer bool now?

quoted

+     if (!bcap_dev->started)
+             complete(&bcap_dev->comp);
+     else {
+             if (!list_empty(&bcap_dev->dma_queue)) {
+                     bcap_dev->next_frm = list_entry(bcap_dev->dma_queue.next,
+                                             struct bcap_buffer, list);
+                     list_del(&bcap_dev->next_frm->list);
+                     addr = vb2_plane_cookie(&bcap_dev->next_frm->vb, 0);

I think, the direct use of vb2_plane_cookie() is discouraged.
vb2_dma_contig_plane_dma_addr() should work for you.

I guess you mean vb2_dma_contig_plane_paddr

quoted

+
+     for (i = 0; i < BCAP_MAX_FMTS; i++) {
+             if (mbus_fmt.code == bcap_formats[i].mbus_code) {
+                     bcap_fmt = &bcap_formats[i];
+                     v4l2_fill_pix_format(pixfmt, &mbus_fmt);
+                     pixfmt->bytesperline = pixfmt->width * bcap_fmt->bpp;
+                     pixfmt->sizeimage = pixfmt->bytesperline
+                                             * pixfmt->height;

It seems to me, you're forgetting to fill in ->pixelformat?

yes, add in v2