media: cec: use call_op and check for !unregistered

Use call_(void_)op consistently in the CEC core framework. Ditto
for the cec pin ops. And check if !adap->devnode.unregistered before
calling each op. This avoids calls to ops when the device has been
unregistered and the underlying hardware may be gone.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

media: cec: call enable_adap on s_log_addrs

Don't enable/disable the adapter if the first fh is opened or the
last fh is closed, instead do this when the adapter is configured
or unconfigured, and also when we enter Monitor All or Monitor Pin
mode for the first time or we exit the Monitor All/Pin mode for the
last time.

However, if needs_hpd is true, then do this when the physical
address is set or cleared: in that case the adapter typically is
powered by the HPD, so it really is disabled when the HPD is low.
This case (needs_hpd is true) was already handled in this way, so
this wasn't changed.

The problem with the old behavior was that if the HPD goes low when
no fh is open, and a transmit was in progress, then the adapter would
be disabled, typically stopping the transmit immediately which
leaves a partial message on the bus, which isn't nice and can confuse
some adapters.

It makes much more sense to disable it only when the adapter is
unconfigured and we're not monitoring the bus, since then you really
won't be using it anymore.

To keep track of this store a CEC activation count and call adap_enable
only when it goes from 0 to 1 or back to 0.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

media: cec: fix a deadlock situation

The cec_devnode struct has a lock meant to serialize access
to the fields of this struct. This lock is taken during
device node (un)registration and when opening or releasing a
filehandle to the device node. When the last open filehandle
is closed the cec adapter might be disabled by calling the
adap_enable driver callback with the devnode.lock held.

However, if during that callback a message or event arrives
then the driver will call one of the cec_queue_event()
variants in cec-adap.c, and those will take the same devnode.lock
to walk the open filehandle list.

This obviously causes a deadlock.

This is quite easy to reproduce with the cec-gpio driver since that
uses the cec-pin framework which generated lots of events and uses
a kernel thread for the processing, so when adap_enable is called
the thread is still running and can generate events.

But I suspect that it might also happen with other drivers if an
interrupt arrives signaling e.g. a received message before adap_enable
had a chance to disable the interrupts.

This patch adds a new mutex to serialize access to the fhs list.
When adap_enable() is called the devnode.lock mutex is held, but
not devnode.lock_fhs. The event functions in cec-adap.c will now
use devnode.lock_fhs instead of devnode.lock, ensuring that it is
safe to call those functions from the adap_enable callback.

This specific issue only happens if the last open filehandle is closed
and the physical address is invalid. This is not something that
happens during normal operation, but it does happen when monitoring
CEC traffic (e.g. cec-ctl --monitor) with an unconfigured CEC adapter.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: <stable@vger.kernel.org> # for v5.13 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

media: cec: safely unhook lists in cec_data

smatch warns about data->list not being removed from list:

drivers/media/cec/core/cec-adap.c:926 cec_transmit_msg_fh() warn: '&data->list' not removed from list

It is a false warning, but it doesn't hurt to make the code more robust
and safely unhook data->list and data->xfer_list together with a WARN_ON
if this is actually ever needed (this really shouldn't happen).

Note that fixing the data->list warning just replaced it with a new similar
warning for data->xfer_list, so both needed to be addressed.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

media: cec: add EPOLLPRI in poll() when dev is unregistered

If the CEC device was unregistered, then add EPOLLPRI to
the poll() mask. Otherwise a select() that only waits for
exceptions will not wake up. A select() that waits for
read and/or write events *will* wake up on an EPOLLERR, but
not (for some reason) if it just waits for exceptions.

Strangly the epoll functionality will wakeup on EPOLLERR if
you just wait for an exception, so in this respect select()
and epoll differ.

In the end it doesn't really matter, what matters is that
polling file handles are woken up on device unregistration.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

cec-api: prevent leaking memory through hole in structure

Fix this smatch warning:

drivers/media/cec/core/cec-api.c:156 cec_adap_g_log_addrs() warn: check that 'log_addrs' doesn't leak information (struct has a hole after
'features')

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

media: cec: move the core to a separate directory

In preparation for moving CEC drivers to the CEC directory,
move the core to a separate place.

Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>