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Date:   Fri, 21 Oct 2022 16:10:04 +0100
From:   "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>, devicetree@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: [PATCH net-next 6/7] net: sfp: add sfp_modify_u8() helper

Add a helper to modify bits in a single byte in memory space, and use
it when updating the soft tx-disable flag in the module.

Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
 drivers/net/phy/sfp.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 16bce0ea68d9..921bbedd9b22 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -608,6 +608,22 @@ static int sfp_write(struct sfp *sfp, bool a2, u8 addr, void *buf, size_t len)
 	return sfp->write(sfp, a2, addr, buf, len);
 }
 
+static int sfp_modify_u8(struct sfp *sfp, bool a2, u8 addr, u8 mask, u8 val)
+{
+	int ret;
+	u8 old, v;
+
+	ret = sfp_read(sfp, a2, addr, &old, sizeof(old));
+	if (ret != sizeof(old))
+		return ret;
+
+	v = (old & ~mask) | (val & mask);
+	if (v == old)
+		return sizeof(v);
+
+	return sfp_write(sfp, a2, addr, &v, sizeof(v));
+}
+
 static unsigned int sfp_soft_get_state(struct sfp *sfp)
 {
 	unsigned int state = 0;
@@ -633,17 +649,14 @@ static unsigned int sfp_soft_get_state(struct sfp *sfp)
 
 static void sfp_soft_set_state(struct sfp *sfp, unsigned int state)
 {
-	u8 status;
+	u8 mask = SFP_STATUS_TX_DISABLE_FORCE;
+	u8 val = 0;
 
-	if (sfp_read(sfp, true, SFP_STATUS, &status, sizeof(status)) ==
-		     sizeof(status)) {
-		if (state & SFP_F_TX_DISABLE)
-			status |= SFP_STATUS_TX_DISABLE_FORCE;
-		else
-			status &= ~SFP_STATUS_TX_DISABLE_FORCE;
+	if (state & SFP_F_TX_DISABLE)
+		val |= SFP_STATUS_TX_DISABLE_FORCE;
 
-		sfp_write(sfp, true, SFP_STATUS, &status, sizeof(status));
-	}
+
+	sfp_modify_u8(sfp, true, SFP_STATUS, mask, val);
 }
 
 static void sfp_soft_start_poll(struct sfp *sfp)
-- 
2.30.2

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