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From: yongsuyoo0215@gmail.com
To: mchehab@kernel.org,
	yongsuyoo0215@gmail.com,
	v4bel@theori.io,
	linux-media@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] media: dvb_ca_en50221: Add a returing EBUSY logic into CA_RESET
Date: Fri,  8 Mar 2024 12:13:38 +0000
Message-Id: <20240308121338.1983-1-yongsuyoo0215@gmail.com>
Precedence: bulk

From: Yongsu yoo <yongsuyoo0215@gmail.com>

Signed-off-by:Yongsu Yoo <yongsuyoo0215@gmail.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