linux-kernel - Re: [PATCH] media: dvb_ringbuffer : Fix a bug in dvb

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Date:   Mon, 27 Jun 2022 06:11:53 +0900
From:   유용수 <yongsuyoo0215@...il.com>
To:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        mchehab@...nel.org, Hans Petter Selasky <hps@...asky.org>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        유용수 <yongsuyoo0215@...il.com>
Subject: Re: [PATCH] media: dvb_ringbuffer : Fix a bug in dvb_ringbuffer.c

Hi ~

How is this patch going ?
Can you share current status ?

Thank you


2022년 6월 23일 (목) 오후 7:35, YongSu Yoo <yongsuyoo0215@...il.com>님이 작성:
>
> Signed-off-by:Yongsu Yoo <yongsuyoo0215@...il.com>
>
> The function dvb_ringbuffer_pkt_next in
> /linux-next/drviers/media/dvb-core/dvb_ringbuffer.c,
> which searches the idx of the next valid packet in the ring
> buffer of the ca->slot_info[slot].rx_buffer at
> /linux-next/drivers/media/dvb-core/dvb_ca_en50221.c,
> has the following problem.
> In calculating the amounts of the consumed address of the ring
> buffer, if the read address(rbuf->pread) of the ring buffer is
> smaller than the idx, the amounts of the searched address
> should be (idx - rbuf->pread),
> whereas if the read address(rbuf->pread) of the ring buffer is
> larger than the idx, the amounts of the consumed address should
> be (idx - rbuf->pread + rbug->size). But there exists an
> incorrect logic that the rbug-size was not properly added on
> (idx - rbug->pread) in the later case. With this commit, we
> fixed this bug.
> ---
>  drivers/media/dvb-core/dvb_ringbuffer.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/dvb-core/dvb_ringbuffer.c b/drivers/media/dvb-core/dvb_ringbuffer.c
> index d1d471af0636..7d4558de8e83 100644
> --- a/drivers/media/dvb-core/dvb_ringbuffer.c
> +++ b/drivers/media/dvb-core/dvb_ringbuffer.c
> @@ -335,7 +335,9 @@ ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t*
>                 idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
>         }
>
> -       consumed = (idx - rbuf->pread) % rbuf->size;
> +       consumed = (idx - rbuf->pread);
> +       if (consumed < 0)
> +               consumed += rbuf->size;
>
>         while((dvb_ringbuffer_avail(rbuf) - consumed) > DVB_RINGBUFFER_PKTHDRSIZE) {
>
> --
> 2.17.1
>