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Message-ID: <y5d6hkhdgwprncbnfmznuk5otluqz3vqi6fof6cyr4dc673cqx@5kr6ys6g53ev>
Date: Thu, 17 Apr 2025 11:59:20 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>
Cc: "donald.hunter@...il.com" <donald.hunter@...il.com>, 
	"kuba@...nel.org" <kuba@...nel.org>, "davem@...emloft.net" <davem@...emloft.net>, 
	"Dumazet, Eric" <edumazet@...gle.com>, "pabeni@...hat.com" <pabeni@...hat.com>, 
	"horms@...nel.org" <horms@...nel.org>, "vadim.fedorenko@...ux.dev" <vadim.fedorenko@...ux.dev>, 
	"Nguyen, Anthony L" <anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw" <przemyslaw.kitszel@...el.com>, 
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "saeedm@...dia.com" <saeedm@...dia.com>, 
	"leon@...nel.org" <leon@...nel.org>, "tariqt@...dia.com" <tariqt@...dia.com>, 
	"jonathan.lemon@...il.com" <jonathan.lemon@...il.com>, "richardcochran@...il.com" <richardcochran@...il.com>, 
	"Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>, "Olech, Milena" <milena.olech@...el.com>, 
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>, "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH net-next v2 3/4] dpll: features_get/set callbacks

Thu, Apr 17, 2025 at 11:23:09AM +0200, arkadiusz.kubalewski@...el.com wrote:
>>From: Jiri Pirko <jiri@...nulli.us>
>>Sent: Wednesday, April 16, 2025 2:11 PM
>>
>>Tue, Apr 15, 2025 at 08:15:42PM +0200, arkadiusz.kubalewski@...el.com
>>wrote:
>>>Add new callback ops for a dpll device.
>>>- features_get(..) - to obtain currently configured features from dpll
>>>  device,
>>>- feature_set(..) - to allow dpll device features configuration.
>>>Provide features attribute and allow control over it to the users if
>>>device driver implements callbacks.
>>>
>>>Reviewed-by: Milena Olech <milena.olech@...el.com>
>>>Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
>>>---
>>>v2:
>>>- adapt changes and align wiht new dpll_device_info struct
>>>---
>>> drivers/dpll/dpll_netlink.c | 79 ++++++++++++++++++++++++++++++++++++-
>>> include/linux/dpll.h        |  5 +++
>>> 2 files changed, 82 insertions(+), 2 deletions(-)
>>>
>>>diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c
>>>index 2de9ec08d551..acfdd87fcffe 100644
>>>--- a/drivers/dpll/dpll_netlink.c
>>>+++ b/drivers/dpll/dpll_netlink.c
>>>@@ -126,6 +126,25 @@ dpll_msg_add_mode_supported(struct sk_buff *msg,
>>>struct dpll_device *dpll,
>>> 	return 0;
>>> }
>>>
>>>+static int
>>>+dpll_msg_add_features(struct sk_buff *msg, struct dpll_device *dpll,
>>>+		      struct netlink_ext_ack *extack)
>>>+{
>>>+	const struct dpll_device_ops *ops = dpll_device_ops(dpll);
>>>+	u32 features;
>>>+	int ret;
>>>+
>>>+	if (!ops->features_get)
>>>+		return 0;
>>>+	ret = ops->features_get(dpll, dpll_priv(dpll), &features, extack);
>>>+	if (ret)
>>>+		return ret;
>>>+	if (nla_put_u32(msg, DPLL_A_FEATURES, features))
>>>+		return -EMSGSIZE;
>>>+
>>>+	return 0;
>>>+}
>>>+
>>> static int
>>> dpll_msg_add_lock_status(struct sk_buff *msg, struct dpll_device *dpll,
>>> 			 struct netlink_ext_ack *extack)
>>>@@ -592,6 +611,11 @@ dpll_device_get_one(struct dpll_device *dpll, struct
>>>sk_buff *msg,
>>> 		return ret;
>>> 	if (nla_put_u32(msg, DPLL_A_TYPE, info->type))
>>> 		return -EMSGSIZE;
>>>+	if (nla_put_u32(msg, DPLL_A_CAPABILITIES, info->capabilities))
>>>+		return -EMSGSIZE;
>>>+	ret = dpll_msg_add_features(msg, dpll, extack);
>>>+	if (ret)
>>>+		return ret;
>>>
>>> 	return 0;
>>> }
>>>@@ -747,6 +771,34 @@ int dpll_pin_change_ntf(struct dpll_pin *pin)
>>> }
>>> EXPORT_SYMBOL_GPL(dpll_pin_change_ntf);
>>>
>>>+static int
>>>+dpll_features_set(struct dpll_device *dpll, struct nlattr *a,
>>>+		  struct netlink_ext_ack *extack)
>>>+{
>>>+	const struct dpll_device_info *info = dpll_device_info(dpll);
>>>+	const struct dpll_device_ops *ops = dpll_device_ops(dpll);
>>>+	u32 features = nla_get_u32(a), old_features;
>>>+	int ret;
>>>+
>>>+	if (features && !(info->capabilities & features)) {
>>>+		NL_SET_ERR_MSG_ATTR(extack, a, "dpll device not capable of this
>>>features");
>>>+		return -EOPNOTSUPP;
>>>+	}
>>>+	if (!ops->features_get || !ops->features_set) {
>>>+		NL_SET_ERR_MSG(extack, "dpll device not supporting any
>>>features");
>>>+		return -EOPNOTSUPP;
>>>+	}
>>>+	ret = ops->features_get(dpll, dpll_priv(dpll), &old_features,
>>>extack);
>>>+	if (ret) {
>>>+		NL_SET_ERR_MSG(extack, "unable to get old features value");
>>>+		return ret;
>>>+	}
>>>+	if (old_features == features)
>>>+		return -EINVAL;
>>>+
>>>+	return ops->features_set(dpll, dpll_priv(dpll), features, extack);
>>
>>So you allow to enable/disable them all in once. What if user want to
>>enable feature A and does not care about feature B that may of may not
>>be previously set?
>
>Assumed that user would always request full set.

Ugh.


>
>>How many of the features do you expect to appear in the future. I'm
>>asking because this could be just a bool attr with a separate op to the
>>driver. If we have 3, no problem. Benefit is, you may also extend it
>>easily to pass some non-bool configuration. My point is, what is the
>>benefit of features bitset here?
>>
>
>Not much, at least right now..
>Maybe one similar in nearest feature. Sure, we can go that way.
>
>But you mean uAPI part also have this enabled somehow per feature or
>leave the feature bits there?

I don't see reason for u32/bitfield32 bits here. Just have attr per
feature to enable/disable it, no problem. It will be easier to work with.


>
>Thank you!
>Arkadiusz
>
>>
>>
>>>+}
>>>+
>>> static int
>>> dpll_pin_freq_set(struct dpll_pin *pin, struct nlattr *a,
>>> 		  struct netlink_ext_ack *extack)
>>>@@ -1536,10 +1588,33 @@ int dpll_nl_device_get_doit(struct sk_buff *skb,
>>struct genl_info *info)
>>> 	return genlmsg_reply(msg, info);
>>> }
>>>
>>>+static int
>>>+dpll_set_from_nlattr(struct dpll_device *dpll, struct genl_info *info)
>>>+{
>>>+	struct nlattr *a;
>>>+	int rem, ret;
>>>+
>>>+	nla_for_each_attr(a, genlmsg_data(info->genlhdr),
>>>+			  genlmsg_len(info->genlhdr), rem) {
>>>+		switch (nla_type(a)) {
>>>+		case DPLL_A_FEATURES:
>>>+			ret = dpll_features_set(dpll, a, info->extack);
>>>+			if (ret)
>>>+				return ret;
>>>+			break;
>>>+		default:
>>>+			break;
>>>+		}
>>>+	}
>>>+
>>>+	return 0;
>>>+}
>>>+
>>> int dpll_nl_device_set_doit(struct sk_buff *skb, struct genl_info *info)
>>> {
>>>-	/* placeholder for set command */
>>>-	return 0;
>>>+	struct dpll_device *dpll = info->user_ptr[0];
>>>+
>>>+	return dpll_set_from_nlattr(dpll, info);
>>> }
>>>
>>> int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct
>>>netlink_callback *cb)
>>>diff --git a/include/linux/dpll.h b/include/linux/dpll.h
>>>index 0489464af958..90c743daf64b 100644
>>>--- a/include/linux/dpll.h
>>>+++ b/include/linux/dpll.h
>>>@@ -30,6 +30,10 @@ struct dpll_device_ops {
>>> 				       void *dpll_priv,
>>> 				       unsigned long *qls,
>>> 				       struct netlink_ext_ack *extack);
>>>+	int (*features_set)(const struct dpll_device *dpll, void *dpll_priv,
>>>+			    u32 features, struct netlink_ext_ack *extack);
>>>+	int (*features_get)(const struct dpll_device *dpll, void *dpll_priv,
>>>+			    u32 *features, struct netlink_ext_ack *extack);
>>> };
>>>
>>> struct dpll_pin_ops {
>>>@@ -99,6 +103,7 @@ struct dpll_pin_ops {
>>>
>>> struct dpll_device_info {
>>> 	enum dpll_type type;
>>>+	u32 capabilities;
>>> 	const struct dpll_device_ops *ops;
>>> };
>>>
>>>--
>>>2.38.1
>>>

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