Hi Hans, On 02.01.2017 15:19, Hans Verkuil wrote: > From: Hans Verkuil <hans.verkuil@xxxxxxxxx> > > Add support for video hotplug detect and EDID/ELD notifiers, which is used > to convey information from video drivers to their CEC and audio counterparts. > > Based on an earlier version from Russell King: > > https://patchwork.kernel.org/patch/9277043/ > > The hpd_notifier is a reference counted object containing the HPD/EDID/ELD state > of a video device. > > When a new notifier is registered the current state will be reported to > that notifier at registration time. > > Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> > Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > --- > drivers/video/Kconfig | 3 + > drivers/video/Makefile | 1 + > drivers/video/hpd-notifier.c | 134 +++++++++++++++++++++++++++++++++++++++++++ > include/linux/hpd-notifier.h | 109 +++++++++++++++++++++++++++++++++++ > 4 files changed, 247 insertions(+) > create mode 100644 drivers/video/hpd-notifier.c > create mode 100644 include/linux/hpd-notifier.h > > diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig > index 3c20af9..cddc860 100644 > --- a/drivers/video/Kconfig > +++ b/drivers/video/Kconfig > @@ -36,6 +36,9 @@ config VIDEOMODE_HELPERS > config HDMI > bool > > +config HPD_NOTIFIERS > + bool > + > if VT > source "drivers/video/console/Kconfig" > endif > diff --git a/drivers/video/Makefile b/drivers/video/Makefile > index 9ad3c17..424698b 100644 > --- a/drivers/video/Makefile > +++ b/drivers/video/Makefile > @@ -1,5 +1,6 @@ > obj-$(CONFIG_VGASTATE) += vgastate.o > obj-$(CONFIG_HDMI) += hdmi.o > +obj-$(CONFIG_HPD_NOTIFIERS) += hpd-notifier.o > > obj-$(CONFIG_VT) += console/ > obj-$(CONFIG_LOGO) += logo/ > diff --git a/drivers/video/hpd-notifier.c b/drivers/video/hpd-notifier.c > new file mode 100644 > index 0000000..54f7a6b > --- /dev/null > +++ b/drivers/video/hpd-notifier.c > @@ -0,0 +1,134 @@ > +#include <linux/export.h> > +#include <linux/hpd-notifier.h> > +#include <linux/string.h> > +#include <linux/slab.h> > +#include <linux/list.h> > + > +static LIST_HEAD(hpd_notifiers); > +static DEFINE_MUTEX(hpd_notifiers_lock); > + > +struct hpd_notifier *hpd_notifier_get(struct device *dev) > +{ > + struct hpd_notifier *n; > + > + mutex_lock(&hpd_notifiers_lock); > + list_for_each_entry(n, &hpd_notifiers, head) { > + if (n->dev == dev) { > + mutex_unlock(&hpd_notifiers_lock); I think this place is racy, we have pointer to unprotected area (n->kref), so if concurrent thread calls hpd_notifier_put in this moment &n->kref could be freed and kref_get in the next line will operate on dangling pointer. Am I right? Regards Andrzej > + kref_get(&n->kref); > + return n; > + } > + } > + n = kzalloc(sizeof(*n), GFP_KERNEL); > + if (!n) > + goto unlock; > + n->dev = dev; > + mutex_init(&n->lock); > + BLOCKING_INIT_NOTIFIER_HEAD(&n->notifiers); > + kref_init(&n->kref); > + list_add_tail(&n->head, &hpd_notifiers); > +unlock: > + mutex_unlock(&hpd_notifiers_lock); > + return n; > +} > +EXPORT_SYMBOL_GPL(hpd_notifier_get); > + > +static void hpd_notifier_release(struct kref *kref) > +{ > + struct hpd_notifier *n = > + container_of(kref, struct hpd_notifier, kref); > + > + mutex_lock(&hpd_notifiers_lock); > + list_del(&n->head); > + mutex_unlock(&hpd_notifiers_lock); > + kfree(n->edid); > + kfree(n); > +} > + > +void hpd_notifier_put(struct hpd_notifier *n) > +{ > + kref_put(&n->kref, hpd_notifier_release); > +} > +EXPORT_SYMBOL_GPL(hpd_notifier_put); > + > +int hpd_notifier_register(struct hpd_notifier *n, struct notifier_block *nb) > +{ > + int ret = blocking_notifier_chain_register(&n->notifiers, nb); > + > + if (ret) > + return ret; > + kref_get(&n->kref); > + mutex_lock(&n->lock); > + if (n->connected) { > + blocking_notifier_call_chain(&n->notifiers, HPD_CONNECTED, n); > + if (n->edid_size) > + blocking_notifier_call_chain(&n->notifiers, HPD_NEW_EDID, n); > + if (n->has_eld) > + blocking_notifier_call_chain(&n->notifiers, HPD_NEW_ELD, n); > + } > + mutex_unlock(&n->lock); > + return 0; > +} > +EXPORT_SYMBOL_GPL(hpd_notifier_register); > + > +int hpd_notifier_unregister(struct hpd_notifier *n, struct notifier_block *nb) > +{ > + int ret = blocking_notifier_chain_unregister(&n->notifiers, nb); > + > + if (ret == 0) > + hpd_notifier_put(n); > + return ret; > +} > +EXPORT_SYMBOL_GPL(hpd_notifier_unregister); (...) -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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