On 19/06/2019 14.15, Boris Brezillon wrote:
> From: Hertz Wong <[email protected]>
>
> Add helpers and patch hantro_{drv,v4l2}.c to prepare addition of H264
> decoding support.
>
> Signed-off-by: Hertz Wong <[email protected]>
> Signed-off-by: Boris Brezillon <[email protected]>
> ---
> +
> + /*
> + * Short term pics in descending pic num order, long term ones in
> + * ascending order.
> + */
> + if (!(a->flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM))
> + return b->frame_num - a->frame_num;
> +
> + return a->pic_num - b->pic_num;
> +}
Pet peeve: This works because ->frame_num and ->pic_num are u16, so
their difference is guaranteed to fit in an int.
> +static int b0_ref_list_cmp(const void *ptra, const void *ptrb, const void
> *data)
> +{
> + const struct hantro_h264_reflist_builder *builder = data;
> + const struct v4l2_h264_dpb_entry *a, *b;
> + s32 poca, pocb;
> + u8 idxa, idxb;
> +
> + idxa = *((u8 *)ptra);
> + idxb = *((u8 *)ptrb);
> + a = &builder->dpb[idxa];
> + b = &builder->dpb[idxb];
> +
> + if ((a->flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM) !=
> + (b->flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM)) {
> + /* Short term pics firt. */
> + if (!(a->flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM))
> + return -1;
> + else
> + return 1;
> + }
> +
> + /* Long term pics in ascending pic num order. */
> + if (a->flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM)
> + return a->pic_num - b->pic_num;
> +
> + poca = builder->pocs[idxa];
> + pocb = builder->pocs[idxb];
> +
> + /*
> + * Short term pics with POC < cur POC first in POC descending order
> + * followed by short term pics with POC > cur POC in POC ascending
> + * order.
> + */
> + if ((poca < builder->curpoc) != (pocb < builder->curpoc))
> + return poca - pocb;
> + else if (poca < builder->curpoc)
> + return pocb - poca;
> +
> + return poca - pocb;
> +}
Here, however, poca and pocb are ints. What guarantees that their values
are not more than 2^31 apart? I know absolutely nothing about this code
or what these numbers represent, so it may be obvious that they are
smallish.
Rasmus
