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

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Date: Mon, 27 May 2024 13:56:38 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: yongsuyoo0215@...il.com
Cc: mchehab@...nel.org, 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

On Fri, Mar 08, 2024 at 12:13:38PM +0000, yongsuyoo0215@...il.com wrote:
> From: Yongsu yoo <yongsuyoo0215@...il.com>
> 
> Signed-off-by:Yongsu Yoo <yongsuyoo0215@...il.com>

You've sent several patches that have not recieved any feedback.  Resend
them all as a patchset.

The Signed-off should go at the bottom.  Run your patches through
scripts/checkpatch.pl.

> 
> 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.

A lot of the commit messages are confusing.  It seems from looking at
the patches that you have been testing CA_RESET and fixing the bugs.
Please talk more about how you are finding these bugs?

In this case the bug is that if you call CA_RESET twice before the
first reset has completed then it is a waste of time?  How serious is
this bug for normal users?  How much time are we talking about?

regards,
dan carpenter