linux-kernel - Re: [PATCH] media: dvb_ca_en50221: Add a returing EBUSY logic into CA

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Message-ID: <CANXPkT6Bcj0Xbn308jNGp-vqTEcB9LKtUjZ1_zS-tc7KuBEMwA@mail.gmail.com>
Date: Thu, 11 Apr 2024 21:02:45 +0900
From: YongSu Yoo <yongsuyoo0215@...il.com>
To: mchehab@...nel.org, yongsuyoo0215@...il.com, v4bel@...ori.io, 
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: dvb_ca_en50221: Add a returing EBUSY logic into CA_RESET

Dear All

Can you review this patch ?
Can you share how this modification is going ?

2024년 3월 8일 (금) 오후 9:13, <yongsuyoo0215@...il.com>님이 작성:
>
> From: Yongsu yoo <yongsuyoo0215@...il.com>
>
> Signed-off-by:Yongsu Yoo <yongsuyoo0215@...il.com>
>
> In source/drivers/media/dvb-core/dvb_ca_en50221.c, if the CA_RESET ioctl
> is called, in a normal case, the state of the thread of the
> dvb_ca_en50221_thread_state_machine will transit like below order.
> DVB_CA_SLOTSTATE_NONE -> DVB_CA_SLOTSTATE_UNINITIALISED ->
> DVB_CA_SLOTSTATE_WAITREADY -> DVB_CA_SLOTSTATE_VALIDATE ->
> DVB_CA_SLOTSTATE_WAITFR -> DVB_CA_SLOTSTATE_LINKINIT ->
> DVB_CA_SLOTSTATE_RUNNING
> But in some problem cases, the state will become DVB_CA_SLOTSTATE_INVALID.
> Among the above mentioned states, the DVB_CA_SLOTSTATE_NONE and
> the DVB_CA_SLOTSTATE_INVALID are "already stablized" states,
> whereas other states are "transiting" states.
> The "already stablized" states mean no matter how long time we wait,
> the state will not be changed.
> The "transiting" states mean the states whose final state is not yet
> determined. The state keeps to be changed. Only after some time passes,
> we get to know whether the final state will be DVB_CA_SLOTSTATE_RUNNING
> or DVB_CA_SLOTSTATE_INVALID.
> During the "transiting" states, we do not yet know whether the
> CA_RESET operation, which triggered the "transiting" states, will
> succeed or fail. For this reason, during the "transiting" states, if
> another CA_RESET ioctl is called and if this new CA_RESET ioctl
> operation begins again, it will be meaningless and waste time.
> For preventing this problem from happening, we make CA_RESET ioctl do
> nothing and only return EBUSY if the ioctl is called during the
> "transiting" states.
> ---
>  drivers/media/dvb-core/dvb_ca_en50221.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/dvb-core/dvb_ca_en50221.c b/drivers/media/dvb-core/dvb_ca_en50221.c
> index baf64540dc00..2e8aec354b7c 100644
> --- a/drivers/media/dvb-core/dvb_ca_en50221.c
> +++ b/drivers/media/dvb-core/dvb_ca_en50221.c
> @@ -1362,13 +1362,19 @@ static int dvb_ca_en50221_io_do_ioctl(struct file *file,
>                         struct dvb_ca_slot *sl = &ca->slot_info[slot];
>
>                         mutex_lock(&sl->slot_lock);
> -                       if (sl->slot_state != DVB_CA_SLOTSTATE_NONE) {
> +                       if ((sl->slot_state == DVB_CA_SLOTSTATE_RUNNING) ||
> +                           (sl->slot_state == DVB_CA_SLOTSTATE_INVALID)) {
>                                 dvb_ca_en50221_slot_shutdown(ca, slot);
>                                 if (ca->flags & DVB_CA_EN50221_FLAG_IRQ_CAMCHANGE)
>                                         dvb_ca_en50221_camchange_irq(ca->pub,
>                                                                      slot,
>                                                                      DVB_CA_EN50221_CAMCHANGE_INSERTED);
>                         }
> +                       else {
> +                               if (sl->slot_state != DVB_CA_SLOTSTATE_NONE) {
> +                                       err = -EBUSY;
> +                               }
> +                       }
>                         mutex_unlock(&sl->slot_lock);
>                 }
>                 ca->next_read_slot = 0;
> --
> 2.17.1
>