netdev - [PATCH net-next v2] net: usb: sr9700: remove code to drive nonexistent multicast filter

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Message-ID: <20260130055123.19269-1-enelsonmoore@gmail.com>
Date: Thu, 29 Jan 2026 21:51:13 -0800
From: Ethan Nelson-Moore <enelsonmoore@...il.com>
To: netdev@...r.kernel.org,
	linux-usb@...r.kernel.org
Cc: Ethan Nelson-Moore <enelsonmoore@...il.com>,
	Simon Horman <horms@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Peter Korsgaard <peter@...sgaard.com>
Subject: [PATCH net-next v2] net: usb: sr9700: remove code to drive nonexistent multicast filter

Several registers referenced in this driver's source code do not
actually exist (they are not writable and read as zero in my testing).
They exist in this driver because it originated as a copy of the dm9601
driver. Notably, these include the multicast filter registers - this
causes the driver to not support multicast packets correctly. Remove
the multicast filter code and register definitions. Instead, set the
chip to receive all multicast filter packets when any multicast
addresses are in the list.

Reviewed-by: Simon Horman <horms@...nel.org> (from v1)
Signed-off-by: Ethan Nelson-Moore <enelsonmoore@...il.com>
---
Changes in v2:
Remove unrelated cleanups; adjust commit message
Use netdev_mc_empty()

(I decided to send this now instead of when I finish my
patch series because it fixes an important functional issue.)

 drivers/net/usb/sr9700.c | 25 ++++---------------------
 drivers/net/usb/sr9700.h |  7 +------
 2 files changed, 5 insertions(+), 27 deletions(-)

diff --git a/drivers/net/usb/sr9700.c b/drivers/net/usb/sr9700.c
index 49764bcf0912..937e6fef3ac6 100644
--- a/drivers/net/usb/sr9700.c
+++ b/drivers/net/usb/sr9700.c
@@ -17,7 +17,6 @@
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>
 #include <linux/usb.h>
-#include <linux/crc32.h>
 #include <linux/usb/usbnet.h>
 
 #include "sr9700.h"
@@ -231,31 +230,15 @@ static const struct ethtool_ops sr9700_ethtool_ops = {
 static void sr9700_set_multicast(struct net_device *netdev)
 {
 	struct usbnet *dev = netdev_priv(netdev);
-	/* We use the 20 byte dev->data for our 8 byte filter buffer
-	 * to avoid allocating memory that is tricky to free later
-	 */
-	u8 *hashes = (u8 *)&dev->data;
 	/* rx_ctl setting : enable, disable_long, disable_crc */
 	u8 rx_ctl = RCR_RXEN | RCR_DIS_CRC | RCR_DIS_LONG;
 
-	memset(hashes, 0x00, SR_MCAST_SIZE);
-	/* broadcast address */
-	hashes[SR_MCAST_SIZE - 1] |= SR_MCAST_ADDR_FLAG;
-	if (netdev->flags & IFF_PROMISC) {
+	if (netdev->flags & IFF_PROMISC)
 		rx_ctl |= RCR_PRMSC;
-	} else if (netdev->flags & IFF_ALLMULTI ||
-		   netdev_mc_count(netdev) > SR_MCAST_MAX) {
-		rx_ctl |= RCR_RUNT;
-	} else if (!netdev_mc_empty(netdev)) {
-		struct netdev_hw_addr *ha;
-
-		netdev_for_each_mc_addr(ha, netdev) {
-			u32 crc = ether_crc(ETH_ALEN, ha->addr) >> 26;
-			hashes[crc >> 3] |= 1 << (crc & 0x7);
-		}
-	}
+	else if (netdev->flags & IFF_ALLMULTI || !netdev_mc_empty(netdev))
+		/* The chip has no multicast filter */
+		rx_ctl |= RCR_ALL;
 
-	sr_write_async(dev, SR_MAR, SR_MCAST_SIZE, hashes);
 	sr_write_reg_async(dev, SR_RCR, rx_ctl);
 }
 
diff --git a/drivers/net/usb/sr9700.h b/drivers/net/usb/sr9700.h
index 5c04ea0306c7..d1663cb1e8cd 100644
--- a/drivers/net/usb/sr9700.h
+++ b/drivers/net/usb/sr9700.h
@@ -101,9 +101,7 @@
 #define		WCR_LINKEN		(1 << 5)
 /* Physical Address Reg */
 #define	SR_PAR			0x10	/* 0x10 ~ 0x15 6 bytes for PAR */
-/* Multicast Address Reg */
-#define	SR_MAR			0x16	/* 0x16 ~ 0x1D 8 bytes for MAR */
-/* 0x1e unused */
+/* 0x16 --> 0x1E unused */
 /* Phy Reset Reg */
 #define	SR_PRR			0x1F
 #define		PRR_PHY_RST		(1 << 0)
@@ -158,9 +156,6 @@
 /* parameters */
 #define	SR_EEPROM_TIMEOUT	1000
 #define	SR_EEPROM_LEN		256
-#define	SR_MCAST_SIZE		8
-#define	SR_MCAST_ADDR_FLAG	0x80
-#define	SR_MCAST_MAX		64
 #define	SR_TX_OVERHEAD		2	/* 2bytes header */
 #define	SR_RX_OVERHEAD		7	/* 3bytes header + 4crc tail */
 
-- 
2.43.0