From: Boris Brezillon <boris.brezillon@collabora.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
Hans Verkuil <hans.verkuil@cisco.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Sakari Ailus <sakari.ailus@iki.fi>,
linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
Tomasz Figa <tfiga@chromium.org>,
Nicolas Dufresne <nicolas@ndufresne.ca>,
kernel@collabora.com,
Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
Ezequiel Garcia <ezequiel@collabora.com>,
Jonas Karlman <jonas@kwiboo.se>,
linux-rockchip@lists.infradead.org,
Heiko Stuebner <heiko@sntech.de>,
Andrew Morton <akpm@linux-foundation.org>,
Philipp Zabel <p.zabel@pengutronix.de>,
Hertz Wong <hertz.wong@rock-chips.com>
Subject: Re: [PATCH 7/9] media: hantro: Add core bits to support H264 decoding
Date: Fri, 26 Jul 2019 12:06:58 +0200 [thread overview]
Message-ID: <20190726120658.53022c21@collabora.com> (raw)
In-Reply-To: <25cc2826-fc8f-570a-07fa-8cbdb11830a7@rasmusvillemoes.dk>
On Thu, 25 Jul 2019 15:31:41 +0200
Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
> On 19/06/2019 14.15, Boris Brezillon wrote:
> > From: Hertz Wong <hertz.wong@rock-chips.com>
> >
> > Add helpers and patch hantro_{drv,v4l2}.c to prepare addition of H264
> > decoding support.
> >
> > Signed-off-by: Hertz Wong <hertz.wong@rock-chips.com>
> > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> > ---
> > +
> > + /*
> > + * 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?
Good question. Both should normally be >= 0, which I guess prevents the
s32 overflow. This being said, it's something passed by userspace, and
I don't think we check the value (yet).
> I know absolutely nothing about this code
> or what these numbers represent, so it may be obvious that they are
> smallish.
Well, a safe approach would be to replace those subtraction by a
ternary operator.
next prev parent reply other threads:[~2019-07-26 10:07 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-19 12:15 [PATCH 0/9] media: hantro: Add support for H264 decoding Boris Brezillon
2019-06-19 12:15 ` [PATCH 1/9] lib/sort.c: implement sort() variant taking context argument Boris Brezillon
2019-07-25 12:40 ` Boris Brezillon
2019-07-26 0:05 ` Andrew Morton
2019-07-26 6:59 ` Rasmus Villemoes
2019-06-19 12:15 ` [PATCH 2/9] media: hantro: Move copy_metadata() before doing a decode operation Boris Brezillon
2019-06-19 12:15 ` [PATCH 3/9] media: hantro: Constify the control array Boris Brezillon
2019-07-05 16:05 ` Ezequiel Garcia
2019-07-05 17:17 ` Boris Brezillon
2019-06-19 12:15 ` [PATCH 4/9] media: hantro: Simplify the controls creation logic Boris Brezillon
2019-06-19 12:15 ` [PATCH 5/9] media: hantro: Add hantro_get_{src,dst}_buf() helpers Boris Brezillon
2019-06-19 12:15 ` [PATCH 6/9] media: hantro: Add helpers to prepare/finish a run Boris Brezillon
2019-06-19 12:15 ` [PATCH 7/9] media: hantro: Add core bits to support H264 decoding Boris Brezillon
2019-07-25 13:31 ` Rasmus Villemoes
2019-07-26 10:06 ` Boris Brezillon [this message]
2019-08-01 4:06 ` Tomasz Figa
2019-08-01 5:42 ` Boris Brezillon
2019-08-01 7:04 ` Paul Kocialkowski
2019-08-01 7:12 ` Tomasz Figa
2019-08-05 18:38 ` Ezequiel Garcia
2019-06-19 12:15 ` [PATCH 8/9] media: hantro: Add support for H264 decoding on G1 Boris Brezillon
2019-06-19 12:15 ` [PATCH 9/9] media: hantro: Enable H264 decoding on rk3288 Boris Brezillon
2019-06-19 12:23 ` [PATCH 0/9] media: hantro: Add support for H264 decoding Boris Brezillon
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