Re: [PATCH] drm/bridge: dw_hdmi: add cec notifier support

From: Russell King - ARM Linux
Date: Thu Jul 06 2017 - 09:39:02 EST

On Thu, Jul 06, 2017 at 12:56:43PM +0100, Russell King - ARM Linux wrote:
> On Thu, Jul 06, 2017 at 12:45:55PM +0100, Russell King - ARM Linux wrote:
> > Well, from what I can see in 4.12, the cec-notifier stuff is rather
> > broken (tda998x has stopped working as its stuck with a physical
> > address of f.f.f.f) so I think the whole thing is rather moot right
> > now. I don't yet know what's going on with that, other than the
> > notifier stuff seems to not be working, despite being enabled in
> > the .config.
> The problem there appears to be the changes that were made with the
> way the config works - which IMHO are totally broken.
> Let's take this scenario:
> - You have a HDMI bridge, and you build that into the kernel, because you
> want the display to come up early.
> - You have a CEC driver, which you build as a module.
> If the HDMI bridge driver selects CEC_NOTIFIER and the CEC driver selects
> both CEC_NOTIFIER and CEC_CORE, you end up with CEC_NOTIFIER=y and
> We now come to this:
> The definition of IS_REACHABLE() is that it is false if the config symbol
> is selected as a module. So, in this case, we end up compiling out all
> the CEC notifier functions from the HDMI bridge, and building them into
> the CEC driver.
> The CEC notifier also gets built as a module, meaning that there's no way
> for the built-in HDMI bridge could ever call the notifier.
> The overall result of this is that such a configuration completely breaks
> such a setup - a setup that worked fine before the CEC Kconfig changes.
> This isn't limited to tda998x - I'd expect the same to be true of dw-hdmi.

Fixing this so cec-notifier is built-in isn't sufficient, because we
also need the cec-edid parsing code as well, which is currently part
of cec-core, and that function gets stubbed out if cec-core is not

The patch below works for me.

drivers/media/Makefile | 2 +-
drivers/media/cec/Makefile | 6 +++---
drivers/media/cec/cec-core.c | 2 +-
3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/media/Makefile b/drivers/media/Makefile
index 044503aa8801..0c02fbe4b9c7 100644
--- a/drivers/media/Makefile
+++ b/drivers/media/Makefile
@@ -24,7 +24,7 @@ obj-$(CONFIG_DVB_CORE) += dvb-core/
# There are both core and drivers at RC subtree - merge before drivers
obj-y += rc/

-obj-$(CONFIG_CEC_CORE) += cec/
+obj-y += cec/

# Finally, merge the drivers that require the core
diff --git a/drivers/media/cec/Makefile b/drivers/media/cec/Makefile
index eaf408e64669..58394b77a328 100644
--- a/drivers/media/cec/Makefile
+++ b/drivers/media/cec/Makefile
@@ -1,7 +1,7 @@
cec-objs := cec-core.o cec-adap.o cec-api.o cec-edid.o

- cec-objs += cec-notifier.o
+obj-$(CONFIG_CEC_NOTIFIER) += cec-notifier.o cec-edid.o
+# Remove cec-edid from cec-core if the notifier is enabled
+cec-objs := $(filter-out $(obj-y) $(obj-m), $(cec-objs))

obj-$(CONFIG_CEC_CORE) += cec.o
diff --git a/drivers/media/cec/cec-core.c b/drivers/media/cec/cec-core.c
index 2f87748ba4fc..bce26b94c348 100644
--- a/drivers/media/cec/cec-core.c
+++ b/drivers/media/cec/cec-core.c
@@ -187,7 +187,7 @@ static void cec_devnode_unregister(struct cec_devnode *devnode)

static void cec_cec_notify(struct cec_adapter *adap, u16 pa)
cec_s_phys_addr(adap, pa, false);

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