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Date: Wed, 29 Mar 2017 16:06:13 +0900 From: Chanwoo Choi <cw00.choi@...sung.com> To: Hans de Goede <hdegoede@...hat.com>, MyungJoo Ham <myungjoo.ham@...sung.com> Cc: linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] extcon: Allow registering a single notifier for all cables on an extcon_dev Hi, On 2017년 03월 25일 23:03, Hans de Goede wrote: > Hi, > > On 20-03-17 10:48, Hans de Goede wrote: >> Hi, >> >> On 20-03-17 01:55, Chanwoo Choi wrote: >>> Hi, >>> >>> On 2017년 03월 20일 03:23, Hans de Goede wrote: >>>> In some cases a driver may want to monitor multiple cables on a single >>>> extcon. For example a charger driver will typically want to monitor all >>>> of EXTCON_CHG_USB_SDP, EXTCON_CHG_USB_CDP, EXTCON_CHG_USB_DCP to configure >>>> the max. current it can sink while charging. >>>> >>>> Due to the signature of the notifier_call function + how extcon passes >>>> state and the extcon_dev as parameters this requires using one >>>> notifier_block + one notifier_call function per cable, otherwise the >>>> notifier_call function cannot get to its driver's data (using container_of >>>> requires it to know which notifier block its first parameter is). >>>> >>>> For a driver wanting to monitor the above 3 cables that would result >>>> in something like this: >>>> >>>> static const unsigned int vbus_cable_ids[] = { >>>> EXTCON_CHG_USB_SDP, EXTCON_CHG_USB_CDP, EXTCON_CHG_USB_DCP }; >>>> >>>> struct driver_data { >>>> struct notifier_block vbus_nb[ARRAY_SIZE(vbus_cable_ids)]; >>>> } >>>> >>>> /* >>>> * We need 3 copies of this, because there is no way to find out for which >>>> * cable id we are being called from the passed in arguments; and we must >>>> * have a separate nb for each extcon_register_notifier call. >>>> */ >>>> static int vbus_cable0_evt(struct notifier_block *nb, unsigned long e, void *p) >>>> { >>>> struct driver_data *data = >>>> container_of(nb, struct driver_data, vbus_nb[0]); >>>> ... >>>> } >>>> >>>> static int vbus_cable1_evt(struct notifier_block *nb, unsigned long e, void *p) >>>> { >>>> struct driver_data *data = >>>> container_of(nb, struct driver_data, vbus_nb[1]); >>>> ... >>>> } >>>> >>>> static int vbus_cable2_evt(struct notifier_block *nb, unsigned long e, void *p) >>>> { >>>> struct driver_data *data = >>>> container_of(nb, struct driver_data, vbus_nb[2]); >>>> ... >>>> } >>>> >>>> int probe(...) >>>> { >>>> /* Register for vbus notification */ >>>> data->vbus_nb[0].notifier_call = vbus_cable0_evt; >>>> data->vbus_nb[1].notifier_call = vbus_cable1_evt; >>>> data->vbus_nb[2].notifier_call = vbus_cable2_evt; >>>> for (i = 0; i < ARRAY_SIZE(vbus_cable_ids); i++) { >>>> ret = devm_extcon_register_notifier(dev, data->vbus_extcon, >>>> vbus_cable_ids[i], &data->vbus_nb[i]); >>>> if (ret) >>>> ... >>>> } >>>> } >>> >>> You can get the notification for multiple external connector >>> by using the only one notifier_block as following: >>> >>> static const unsigned int vbus_cable_ids[] = { >>> EXTCON_CHG_USB_SDP, EXTCON_CHG_USB_CDP, EXTCON_CHG_USB_DCP }; >>> >>> struct driver_data { >>> struct notifier_block vbus_nb; >>> } >>> >>> static int vbus_cable_evt(struct notifier_block *nb, unsigned long e, void *p) >>> { >>> struct driver_data *data = >>> container_of(nb, struct driver_data, vbus_nb); >>> int sdp_state, cdp_state, dcp_state; >>> >>> sdp_state = extcon_get_state(data->vbus_extcon, EXTCON_CHG_USB_SDP); >>> cdp_state = extcon_get_state(data->vbus_extcon, EXTCON_CHG_USB_CDP); >>> dcp_state = extcon_get_state(data->vbus_extcon, EXTCON_CHG_USB_DCP); >>> >>> ... >>> } >>> >>> int probe(...) >>> { >>> /* Register for vbus notification */ >>> data->vbus_nb.notifier_call = vbus_cable_evt; >>> for (i = 0; i < ARRAY_SIZE(vbus_cable_ids); i++) { >>> ret = devm_extcon_register_notifier(dev, data->vbus_extcon, >>> vbus_cable_ids[i], &data->vbus_nb); >>> if (ret) >>> ... >>> } >>> } >> >> No that will not work, you cannot add the same notifier_block to 3 >> different notifier_heads, the list_head can only be part of one list! >> >> Also see: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/power/supply?id=577b1f06e22057e9cdc14b1ee5bd25435c71ff0f >> >> Which actually fixes an issue I encountered exactly because of doing >> the above. >> >> So we really need something like my patch to make this simpler >> and to remove the ugliness we currently have in axp288_charger.c >> because of this problem (and are about to have in more drivers >> I'm upstreaming). Also note that my patch is quite simple, the >> amount of lines it adds is way less then the amount of lines >> it will allow to remove in a single driver! > > Ping ? > > As explained this is a real problem and we really need a proper solution > for this. I'm about to upstream 2 more drivers which need to monitor > an antire extcon rather then a single cable on it, and I do not want > to have to add hacks like this: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/power/supply?id=577b1f06e22057e9cdc14b1ee5bd25435c71ff0f > > To both drivers. My patch is IMHO a nice and clean solution for this, > can you please merge this or provide an alternative solution ? As you said, when using one notifier_block for multiple external connector, it has a problem. But, it is not only for extcon framework. It depends on the notifier_block code. If each external connector uses the each notifier_block (it is a not hack), there is no any problem. As I already said on my reply[1] as following, --------------------------------------------- The extcon_register_notifier() function must support the notification for only one external connector. [1] https://www.spinics.net/lists/kernel/msg2468906.html --------------------------------------------- I agree that the EXTCON needs to support the notification for all supported external connector of extcon device by using only one notifier_chain. I don't prefer to use the '-1' as the unique id for getting the notification for all external connectors. Each argument of function must have the correct meaning. I think that thanks for your report and suggestion. I'm considering to add the new function as following: Following function will support the all external connector for notification and the function argument don't include the unique id for external connector. - extcon_regiter_all_notifier(struct extcon_dev *edev, struct notifier_block *nb); (The function name is not fixed) > > Regards, > > Hans > > > > >> >> Regards, >> >> Hans >> >> >>>> >>>> And then in the event handling the driver often checks the state of >>>> all cables explicitly using extcon_get_state, rather then using the >>>> event argument to the notifier_call. >>>> >>>> This commit makes extcon_[un]register_notifier accept -1 as cable-id, >>>> which will cause the notifier to get called for changes on any cable >>>> on the extcon_dev. Compared to the above example code this allows much >>>> simpler code in drivers which want to monitor multiple cable types. >>>> >>>> Signed-off-by: Hans de Goede <hdegoede@...hat.com> >>>> --- >>>> Changes in v2: >>>> -Fix false-positive "warning: 'idx' may be used uninitialized" warning >>>> seen with some compiler versions >>>> --- >>>> drivers/extcon/extcon.c | 35 ++++++++++++++++++++++++++--------- >>>> drivers/extcon/extcon.h | 1 + >>>> 2 files changed, 27 insertions(+), 9 deletions(-) >>>> >>>> diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c >>>> index 09ac5e7..2a042ee 100644 >>>> --- a/drivers/extcon/extcon.c >>>> +++ b/drivers/extcon/extcon.c >>>> @@ -449,6 +449,7 @@ int extcon_sync(struct extcon_dev *edev, unsigned int id) >>>> >>>> state = !!(edev->state & BIT(index)); >>>> raw_notifier_call_chain(&edev->nh[index], state, edev); >>>> + raw_notifier_call_chain(&edev->nh_all, 0, edev); >>>> >>>> /* This could be in interrupt handler */ >>>> prop_buf = (char *)get_zeroed_page(GFP_ATOMIC); >>>> @@ -900,6 +901,8 @@ EXPORT_SYMBOL_GPL(extcon_get_extcon_dev); >>>> * any attach status changes from the extcon. >>>> * @edev: the extcon device that has the external connecotr. >>>> * @id: the unique id of each external connector in extcon enumeration. >>>> + * or -1 to get notififications for all cables on edev, in this >>>> + * case no state info will get passed to the notifier_call. >>>> * @nb: a notifier block to be registered. >>>> * >>>> * Note that the second parameter given to the callback of nb (val) is >>>> @@ -915,12 +918,18 @@ int extcon_register_notifier(struct extcon_dev *edev, unsigned int id, >>>> if (!edev || !nb) >>>> return -EINVAL; >>>> >>>> - idx = find_cable_index_by_id(edev, id); >>>> - if (idx < 0) >>>> - return idx; >>>> + if ((int)id != -1) { >>>> + idx = find_cable_index_by_id(edev, id); >>>> + if (idx < 0) >>>> + return idx; >>>> + } >>>> >>>> spin_lock_irqsave(&edev->lock, flags); >>>> - ret = raw_notifier_chain_register(&edev->nh[idx], nb); >>>> + if ((int)id != -1) >>>> + ret = raw_notifier_chain_register(&edev->nh[idx], nb); >>>> + else >>>> + ret = raw_notifier_chain_register(&edev->nh_all, nb); >>>> + >>>> spin_unlock_irqrestore(&edev->lock, flags); >>>> >>>> return ret; >>>> @@ -937,17 +946,23 @@ int extcon_unregister_notifier(struct extcon_dev *edev, unsigned int id, >>>> struct notifier_block *nb) >>>> { >>>> unsigned long flags; >>>> - int ret, idx; >>>> + int ret, idx = 0; >>>> >>>> if (!edev || !nb) >>>> return -EINVAL; >>>> >>>> - idx = find_cable_index_by_id(edev, id); >>>> - if (idx < 0) >>>> - return idx; >>>> + if ((int)id != -1) { >>>> + idx = find_cable_index_by_id(edev, id); >>>> + if (idx < 0) >>>> + return idx; >>>> + } >>>> >>>> spin_lock_irqsave(&edev->lock, flags); >>>> - ret = raw_notifier_chain_unregister(&edev->nh[idx], nb); >>>> + if ((int)id != -1) >>>> + ret = raw_notifier_chain_unregister(&edev->nh[idx], nb); >>>> + else >>>> + ret = raw_notifier_chain_unregister(&edev->nh_all, nb); >>>> + >>>> spin_unlock_irqrestore(&edev->lock, flags); >>>> >>>> return ret; >>>> @@ -1212,6 +1227,8 @@ int extcon_dev_register(struct extcon_dev *edev) >>>> for (index = 0; index < edev->max_supported; index++) >>>> RAW_INIT_NOTIFIER_HEAD(&edev->nh[index]); >>>> >>>> + RAW_INIT_NOTIFIER_HEAD(&edev->nh_all); >>>> + >>>> dev_set_drvdata(&edev->dev, edev); >>>> edev->state = 0; >>>> >>>> diff --git a/drivers/extcon/extcon.h b/drivers/extcon/extcon.h >>>> index 993ddcc..2e6c09d 100644 >>>> --- a/drivers/extcon/extcon.h >>>> +++ b/drivers/extcon/extcon.h >>>> @@ -44,6 +44,7 @@ struct extcon_dev { >>>> /* Internal data. Please do not set. */ >>>> struct device dev; >>>> struct raw_notifier_head *nh; >>>> + struct raw_notifier_head nh_all; >>>> struct list_head entry; >>>> int max_supported; >>>> spinlock_t lock; /* could be called by irq handler */ >>>> >>> >>> > > -- Best Regards, Chanwoo Choi Samsung Electronics
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