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Date: Thu, 4 Apr 2024 10:38:25 +0200
From: Maxime Chevallier <maxime.chevallier@bootlin.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: davem@davemloft.net, netdev@vger.kernel.org,
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Subject: Re: [PATCH net-next v10 07/13] net: ethtool: Introduce a command to
 list PHYs on an interface
Message-ID: <20240404103825.6a596bec@device-28.home>
In-Reply-To: <20240308211842.6d64b5bc@kernel.org>
References: <20240304151011.1610175-1-maxime.chevallier@bootlin.com>
	<20240304151011.1610175-8-maxime.chevallier@bootlin.com>
	<20240308211842.6d64b5bc@kernel.org>
Organization: Bootlin
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Hello Jakub,

Sorry for the late reply...

On Fri, 8 Mar 2024 21:18:42 -0800
Jakub Kicinski <kuba@kernel.org> wrote:

> On Mon,  4 Mar 2024 16:10:03 +0100 Maxime Chevallier wrote:
> > +PHY_GET
> > +=======
> > +
> > +Retrieve information about a given Ethernet PHY sitting on the link. As there
> > +can be more than one PHY, the DUMP operation can be used to list the PHYs
> > +present on a given interface, by passing an interface index or name in
> > +the dump request  
> 
> Could be worth re-stating the default behavior of the DO request?
> That the DO will return the dev->phydev by default and if PHY_INDEX
> is specified in the header, the particular PHY with that index?
> 
> > +	if (phydev->drv && nla_put_string(skb, ETHTOOL_A_PHY_DRVNAME, phydev->drv->name))  
> 
> could you break the lines at 80 where it doesn't hurt readability?
> This way:
> 
> 	if (phydev->drv && 
> 	    nla_put_string(skb, ETHTOOL_A_PHY_DRVNAME, phydev->drv->name))

Ack, will do

> 
> > +		return -EMSGSIZE;
> > +
> > +	if (ptype == PHY_UPSTREAM_PHY) {
> > +		struct phy_device *upstream = pdn->upstream.phydev;
> > +		const char *sfp_upstream_name;
> > +
> > +		/* Parent index */
> > +		if (nla_put_u32(skb, ETHTOOL_A_PHY_UPSTREAM_INDEX, upstream->phyindex))
> > +			return -EMSGSIZE;
> > +
> > +		if (pdn->parent_sfp_bus) {
> > +			sfp_upstream_name = sfp_get_name(pdn->parent_sfp_bus);
> > +			if (sfp_upstream_name && nla_put_string(skb,
> > +								ETHTOOL_A_PHY_UPSTREAM_SFP_NAME,
> > +								sfp_upstream_name))  
> 
> ditto

Indeed :)

> 
> > +				return -EMSGSIZE;
> > +		}
> > +	}  
> 
> > +int ethnl_phy_doit(struct sk_buff *skb, struct genl_info *info)
> > +{
> > +	struct phy_req_info req_info = {};
> > +	struct nlattr **tb = info->attrs;
> > +	struct sk_buff *rskb;
> > +	void *reply_payload;
> > +	int reply_len;
> > +	int ret;
> > +
> > +	ret = ethnl_parse_header_dev_get(&req_info.base,
> > +					 tb[ETHTOOL_A_PHY_HEADER],
> > +					 genl_info_net(info), info->extack,
> > +					 true);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	rtnl_lock();
> > +
> > +	ret = ethnl_phy_parse_request(&req_info.base, tb);
> > +	if (ret < 0)
> > +		goto err_unlock_rtnl;
> > +
> > +	/* No PHY, return early */
> > +	if (!req_info.pdn.phy)
> > +		goto err_unlock_rtnl;
> > +
> > +	ret = ethnl_phy_reply_size(&req_info.base, info->extack);
> > +	if (ret < 0)
> > +		goto err_unlock_rtnl;
> > +	reply_len = ret + ethnl_reply_header_size();
> > +
> > +	rskb = ethnl_reply_init(reply_len, req_info.base.dev,
> > +				ETHTOOL_MSG_PHY_GET_REPLY,
> > +				ETHTOOL_A_PHY_HEADER,
> > +				info, &reply_payload);
> > +	if (!rskb) {
> > +		ret = -ENOMEM;
> > +		goto err_unlock_rtnl;
> > +	}
> > +
> > +	ret = ethnl_phy_fill_reply(&req_info.base, rskb);
> > +	if (ret)
> > +		goto err_free_msg;
> > +
> > +	rtnl_unlock();
> > +	ethnl_parse_header_dev_put(&req_info.base);
> > +	genlmsg_end(rskb, reply_payload);
> > +
> > +	return genlmsg_reply(rskb, info);
> > +
> > +err_free_msg:
> > +	nlmsg_free(rskb);
> > +err_unlock_rtnl:
> > +	rtnl_unlock();
> > +	ethnl_parse_header_dev_put(&req_info.base);
> > +	return ret;
> > +}
> > +
> > +struct ethnl_phy_dump_ctx {
> > +	struct phy_req_info	*phy_req_info;
> > +	unsigned long ifindex;
> > +	unsigned long phy_index;
> > +};
> > +
> > +int ethnl_phy_start(struct netlink_callback *cb)
> > +{
> > +	const struct genl_dumpit_info *info = genl_dumpit_info(cb);  
> 
> You can save some chars by using genl_info_dump() here
> 
> > +	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
> > +	struct nlattr **tb = info->info.attrs;  
> 
> then you can ditch this
> 
> > +	int ret;
> > +
> > +	BUILD_BUG_ON(sizeof(*ctx) > sizeof(cb->ctx));
> > +
> > +	ctx->phy_req_info = kzalloc(sizeof(*ctx->phy_req_info), GFP_KERNEL);
> > +	if (!ctx->phy_req_info)
> > +		return -ENOMEM;
> > +
> > +	ret = ethnl_parse_header_dev_get(&ctx->phy_req_info->base,
> > +					 tb[ETHTOOL_A_PHY_HEADER],  
> 
> and:
> 
> 					 info->attrs[ETHTOOL_A_PHY_HEADER],

Nice improvement, thanks !

> 
> > +					 sock_net(cb->skb->sk), cb->extack,
> > +					 false);  
> 
> leaking ctx->phy_req_info on error?

Ah true, I relied on .done() but if ret is an error, it won't be
called... thanks !

> 
> > +	ctx->ifindex = 0;
> > +	ctx->phy_index = 0;
> > +	return ret;
> > +}  
> 
> > +static int ethnl_phy_dump_one_dev(struct sk_buff *skb, struct net_device *dev,
> > +				  struct netlink_callback *cb)
> > +{
> > +	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
> > +	struct phy_req_info *pri = ctx->phy_req_info;
> > +	struct phy_device_node *pdn;
> > +	int ret = 0;
> > +	void *ehdr;
> > +
> > +	pri->base.dev = dev;
> > +
> > +	xa_for_each_start(&dev->link_topo->phys, ctx->phy_index, pdn, ctx->phy_index) {
> > +		ehdr = ethnl_dump_put(skb, cb,
> > +				      ETHTOOL_MSG_PHY_GET_REPLY);  
> 
> this one OTOH fits on a line :)
> 
> > +		if (!ehdr) {
> > +			ret = -EMSGSIZE;
> > +			break;
> > +		}
> > +
> > +		ret = ethnl_fill_reply_header(skb, dev,
> > +					      ETHTOOL_A_PHY_HEADER);  
> 
> ditto

Ack for both :)

> 
> > +		if (ret < 0) {
> > +			genlmsg_cancel(skb, ehdr);
> > +			break;
> > +		}
> > +
> > +		memcpy(&pri->pdn, pdn, sizeof(*pdn));
> > +		ret = ethnl_phy_fill_reply(&pri->base, skb);  
> 
> On a DO fill() shouldn't fail, because we size the skb, but if we pack
> many entries into the skb on a DUMP it can. So:
> 
> 		if (ret < 0) {
> 			genlmsg_cancel(skb, ehdr);
> 			break;
> 		}
> 
> no?

True, I'll add that

> 
> > +		genlmsg_end(skb, ehdr);
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +int ethnl_phy_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
> > +{
> > +	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
> > +	struct net *net = sock_net(skb->sk);
> > +	struct net_device *dev;
> > +	int ret = 0;
> > +
> > +	rtnl_lock();
> > +
> > +	if (ctx->phy_req_info->base.dev) {
> > +		ret = ethnl_phy_dump_one_dev(skb, ctx->phy_req_info->base.dev, cb);
> > +	} else {
> > +		for_each_netdev_dump(net, dev, ctx->ifindex) {
> > +			ret = ethnl_phy_dump_one_dev(skb, dev, cb);
> > +			if (ret)
> > +				break;
> > +
> > +			ctx->phy_index = 0;
> > +		}
> > +	}
> > +	rtnl_unlock();
> > +
> > +	if (ret == -EMSGSIZE && skb->len)
> > +		return skb->len;  
> 
> you can remove this if thanks to (very recent) commit b5a899154aa9

Ah nice ! thanks :)

> 
> > +	return ret;
> > +}  
> 
> Very sorry for the late review, BTW :(

No worries. I'll send a new version very shortly, taking all you
comments into account, thanks for taking a look at this !

Maxime