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

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Date:   Mon, 12 Sep 2022 21:31:13 +0900
From:   유용수 <yongsuyoo0215@...il.com>
To:     Hans Petter Selasky <hps@...asky.org>
Cc:     Kieran Bingham <kieran.bingham@...asonboard.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        mchehab@...nel.org, 0215yys@...mail.net,
        유용수 <yongsuyoo0215@...il.com>
Subject: Re: [PATCH] media: dvb_ringbuffer : Fix a bug in dvb_ringbuffer.c

Dear Hans Petter Selasky

Thank you for your sincere replyment.
But I cannot understand what you mean.
Can you kindly explain what kind of C-program do I have to write ?

2022년 9월 9일 (금) 오후 11:46, Hans Petter Selasky <hps@...asky.org>님이 작성:
>
> On 8/31/22 15:45, 유용수 wrote:
> > Dear All,
> >
> > Can you share how this patch is going ?
> >
> > 2022년 8월 18일 (목) 오후 9:55, 유용수 <yongsuyoo0215@...il.com>님이 작성:
> >>
> >> Dear All,
> >>
> >> Can you pay your attention to this patch ?
> >> This is a very simple modification.
> >> But, too much time has already passed since I sent the first E-mail.
> >>
> >> 2022년 8월 3일 (수) 오후 9:04, 유용수 <yongsuyoo0215@...il.com>님이 작성:
> >>>
> >>> Dear All.
> >>> Too much time has already passed since I first sent this Email.
> >>> Can you share how this patch is going ?
> >>>
> >>> 2022년 6월 23일 (목) 오후 6:11, 유용수 <yongsuyoo0215@...il.com>님이 작성:
> >>>>
> >>>> Dear Kieran Bingham
> >>>>
> >>>> I sent E-mail again by Linux terminal by using the command " ... git
> >>>> send-email .."
> >>>> I believe that you will surely get the diff file.
> >>>>
> >>>> Thank you
> >>>>
> >>>> 2022년 6월 22일 (수) 오후 10:12, Hans Petter Selasky <hps@...asky.org>님이 작성:
> >>>>>
> >>>>> Hi Kieran,
> >>>>>
> >>>>> The consumed variable should not be negative. This bug has been there
> >>>>> since the beginning of the GIT at Linux from what I can see.
> >>>>>
> >>>>> +1
> >>>>>
> >>>>> --HPS
> >>>>>
> >>>>>   From 108c6acb2cc4bc4314b96f6f254a04b2873a096c Mon Sep 17 00:00:00 2001
> >>>>> From: YongSu Yoo <yongsuyoo0215@...il.com>
> >>>>> Date: Sun, 22 May 2022 04:53:12 +0000
> >>>>> Subject: [PATCH] media: dvb_ringbuffer : Fix a bug in dvb_ringbuffer.c
> >>>>>
> >>>>> 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
>
> Maybe it will help if you write a test C-program to show the bad numbers
> computed?
>
> --HPS