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From:   Sean Anderson <sean.anderson@seco.com>
To:     netdev@vger.kernel.org, "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, linux-kernel@vger.kernel.org
Cc:     Andrew Lunn <andrew@lunn.ch>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        Sean Anderson <sean.anderson@seco.com>
Subject: [RFC net-next PATCH 06/16] net: phylink: Add function for optionally adding a PCS
Date:   Mon,  4 Oct 2021 15:15:17 -0400
Message-Id: <20211004191527.1610759-7-sean.anderson@seco.com>
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This adds a function to set the PCS only if there is not one currently
set. The intention here is to allow MAC drivers to have a "default" PCS
(such as an internal one) which may be used when one has not been set
via the device tree. This allows for backwards compatibility for cases
where a PCS was automatically attached if necessary.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
---

 drivers/net/phy/phylink.c | 26 ++++++++++++++++++++++++++
 include/linux/phylink.h   |  1 +
 2 files changed, 27 insertions(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 046fdac3597d..f82dc0f87f40 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -871,6 +871,32 @@ int phylink_set_pcs(struct phylink *pl, struct phylink_pcs *pcs)
 }
 EXPORT_SYMBOL_GPL(phylink_set_pcs);
 
+/**
+ * phylink_set_pcs_weak() - optionally set the current PCS for phylink to use
+ * @pl: a pointer to a &struct phylink returned from phylink_create()
+ * @pcs: a pointer to the &struct phylink_pcs
+ *
+ * Bind the MAC PCS to phylink only if there is no currently-bound PCS. This
+ * may be called to set a "default" PCS, such as an internal PCS which was
+ * previously handled by the MAC driver directly. Otherwise, this function
+ * behaves like phylink_set_pcs();
+ *
+ * Context: may sleep.
+ * Return: 1 if the PCS was set, 0 if it was not, or -errno on failure.
+ */
+int phylink_set_pcs_weak(struct phylink *pl, struct phylink_pcs *pcs)
+{
+	int ret;
+
+	if (!pl->pcs) {
+		ret = phylink_set_pcs(pl, pcs);
+		return ret ? ret : 1;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(phylink_set_pcs_weak);
+
 static struct phylink_pcs *phylink_find_pcs(struct fwnode_handle *fwnode)
 {
 	struct phylink_pcs *pcs;
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index d60756b36ad3..bd0ce707d098 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -442,6 +442,7 @@ void pcs_link_up(struct phylink_pcs *pcs, unsigned int mode,
 int phylink_register_pcs(struct phylink_pcs *pcs);
 void phylink_unregister_pcs(struct phylink_pcs *pcs);
 int phylink_set_pcs(struct phylink *pl, struct phylink_pcs *pcs);
+int phylink_set_pcs_weak(struct phylink *pl, struct phylink_pcs *pcs);
 
 struct phylink *phylink_create(struct phylink_config *, struct fwnode_handle *,
 			       phy_interface_t iface,
-- 
2.25.1