netdev - Re: [PATCH net 3/3] dpll: fix register pin with unregistered parent pin

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Date: Thu, 9 Nov 2023 10:56:26 +0000
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>,
 Jiri Pirko <jiri@...nulli.us>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "Michalik, Michal" <michal.michalik@...el.com>,
 "Olech, Milena" <milena.olech@...el.com>,
 "pabeni@...hat.com" <pabeni@...hat.com>, "kuba@...nel.org" <kuba@...nel.org>
Subject: Re: [PATCH net 3/3] dpll: fix register pin with unregistered parent
 pin

On 09/11/2023 09:59, Kubalewski, Arkadiusz wrote:
>> From: Jiri Pirko <jiri@...nulli.us>
>> Sent: Wednesday, November 8, 2023 4:08 PM
>>
>> Wed, Nov 08, 2023 at 11:32:26AM CET, arkadiusz.kubalewski@...el.com wrote:
>>> In case of multiple kernel module instances using the same dpll device:
>>> if only one registers dpll device, then only that one can register
>>
>> They why you don't register in multiple instances? See mlx5 for a
>> reference.
>>
> 
> Every registration requires ops, but for our case only PF0 is able to
> control dpll pins and device, thus only this can provide ops.
> Basically without PF0, dpll is not able to be controlled, as well
> as directly connected pins.
> 
But why do you need other pins then, if FP0 doesn't exist?

>>
>>> directly connected pins with a dpll device. If unregistered parent
>>> determines if the muxed pin can be register with it or not, it forces
>>> serialized driver load order - first the driver instance which
>>> registers the direct pins needs to be loaded, then the other instances
>>> could register muxed type pins.
>>>
>>> Allow registration of a pin with a parent even if the parent was not
>>> yet registered, thus allow ability for unserialized driver instance
>>
>> Weird.
>>
> 
> Yeah, this is issue only for MUX/parent pin part, couldn't find better
> way, but it doesn't seem to break things around..
> 

I just wonder how do you see the registration procedure? How can parent
pin exist if it's not registered? I believe you cannot get it through
DPLL API, then the only possible way is to create it within the same
driver code, which can be simply re-arranged. Am I wrong here?

> Thank you!
> Arkadiusz
> 
>>
>>> load order.
>>> Do not WARN_ON notification for unregistered pin, which can be invoked
>>> for described case, instead just return error.
>>>
>>> Fixes: 9431063ad323 ("dpll: core: Add DPLL framework base functions")
>>> Fixes: 9d71b54b65b1 ("dpll: netlink: Add DPLL framework base
>>> functions")
>>> Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
>>> ---
>>> drivers/dpll/dpll_core.c    | 4 ----
>>> drivers/dpll/dpll_netlink.c | 2 +-
>>> 2 files changed, 1 insertion(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c index
>>> 4077b562ba3b..ae884b92d68c 100644
>>> --- a/drivers/dpll/dpll_core.c
>>> +++ b/drivers/dpll/dpll_core.c
>>> @@ -28,8 +28,6 @@ static u32 dpll_xa_id;
>>> 	WARN_ON_ONCE(!xa_get_mark(&dpll_device_xa, (d)->id, DPLL_REGISTERED))
>>> #define ASSERT_DPLL_NOT_REGISTERED(d)	\
>>> 	WARN_ON_ONCE(xa_get_mark(&dpll_device_xa, (d)->id, DPLL_REGISTERED))
>>> -#define ASSERT_PIN_REGISTERED(p)	\
>>> -	WARN_ON_ONCE(!xa_get_mark(&dpll_pin_xa, (p)->id, DPLL_REGISTERED))
>>>
>>> struct dpll_device_registration {
>>> 	struct list_head list;
>>> @@ -641,8 +639,6 @@ int dpll_pin_on_pin_register(struct dpll_pin *parent,
>> struct dpll_pin *pin,
>>> 	    WARN_ON(!ops->state_on_pin_get) ||
>>> 	    WARN_ON(!ops->direction_get))
>>> 		return -EINVAL;
>>> -	if (ASSERT_PIN_REGISTERED(parent))
>>> -		return -EINVAL;
>>>
>>> 	mutex_lock(&dpll_lock);
>>> 	ret = dpll_xa_ref_pin_add(&pin->parent_refs, parent, ops, priv); diff
>>> --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c index
>>> 963bbbbe6660..ff430f43304f 100644
>>> --- a/drivers/dpll/dpll_netlink.c
>>> +++ b/drivers/dpll/dpll_netlink.c
>>> @@ -558,7 +558,7 @@ dpll_pin_event_send(enum dpll_cmd event, struct
>> dpll_pin *pin)
>>> 	int ret = -ENOMEM;
>>> 	void *hdr;
>>>
>>> -	if (WARN_ON(!xa_get_mark(&dpll_pin_xa, pin->id, DPLL_REGISTERED)))
>>> +	if (!xa_get_mark(&dpll_pin_xa, pin->id, DPLL_REGISTERED))
>>> 		return -ENODEV;
>>>
>>> 	msg = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
>>> --
>>> 2.38.1
>>>