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

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

[Ethan Nelson-Moore]

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 instead set the chip to receive all
multicast filter packets when any multicast addresses are in the list.
Also take the opportunity to remove definitions for a few other
nonexistent registers, and a couple pointless comments.

Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>
---
 drivers/net/usb/sr9700.c | 26 ++++----------------------
 drivers/net/usb/sr9700.h | 19 +++----------------
 2 files changed, 7 insertions(+), 38 deletions(-)

diff --git a/drivers/net/usb/sr9700.c b/drivers/net/usb/sr9700.c
index 9c7cd0db1768..19c36b0d441c 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 +230,14 @@ 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_count(netdev) > 0)
+		/* 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 3212859830dc..51c696108d80 100644
--- a/drivers/net/usb/sr9700.h
+++ b/drivers/net/usb/sr9700.h
@@ -8,8 +8,6 @@
 #ifndef _SR9700_H
 #define	_SR9700_H
 
-/* sr9700 spec. register table on Linux platform */
-
 /* Network Control Reg */
 #define	SR_NCR			0x00
 #define		NCR_RST			(1 << 0)
@@ -101,9 +99,7 @@
 #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)
@@ -123,10 +119,7 @@
 #define	SR_RRPAL		0x26
 /* Rx sdram Read Pointer Address High */
 #define	SR_RRPAH		0x27
-/* Vendor ID register */
-#define	SR_VID			0x28	/* 0x28 ~ 0x29 2 bytes for VID */
-/* Product ID register */
-#define	SR_PID			0x2A	/* 0x2A ~ 0x2B 2 bytes for PID */
+/* 0x28 --> 0x2B unused */
 /* CHIP Revision register */
 #define	SR_CHIPR		0x2C
 /* 0x2D --> 0xEF unused */
@@ -143,10 +136,7 @@
 #define		TXC_USBS_EP1RDY		(1 << 5)
 #define		TXC_USBS_SUSFLAG	(1 << 6)
 #define		TXC_USBS_RXFAULT	(1 << 7)
-/* USB Control register */
-#define	SR_USBC			0xF4
-#define		USBC_EP3NAK		(1 << 4)
-#define		USBC_EP3ACK		(1 << 5)
+/* 0xF4 --> 0xFF unused */
 
 /* Register access commands and flags */
 #define	SR_RD_REGS		0x00
@@ -158,9 +148,6 @@
 /* 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

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

[Simon Horman]

On Thu, Jan 22, 2026 at 10:58:32PM -0800, Ethan Nelson-Moore wrote:
> 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 instead set the chip to receive all
> multicast filter packets when any multicast addresses are in the list.
> Also take the opportunity to remove definitions for a few other
> nonexistent registers, and a couple pointless comments.
> 
> Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>

I would slightly lean towards splitting this patch up,
say one for the multicast changes and removal of related #defines,
and another for the remainder of the #define clean-up.

But that notwithstanding this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

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

[Jakub Kicinski]

On Thu, 22 Jan 2026 22:58:32 -0800 Ethan Nelson-Moore wrote:
> +	else if (netdev->flags & IFF_ALLMULTI || netdev_mc_count(netdev) > 0)

nit: netdev_mc_empty()
-- 
pw-bot: cr

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

[Ethan Nelson-Moore]

On Mon, Jan 26, 2026 at 7:26 PM Jakub Kicinski <kuba@kernel.org> wrote:
> > +     else if (netdev->flags & IFF_ALLMULTI || netdev_mc_count(netdev) > 0)
>
> nit: netdev_mc_empty()

Hi, Jakub,

Thanks for noticing - I don't know how I missed that, given that the
original code was using it.

I have adjusted this patch to use netdev_mc_empty. It is now part of a
series of sr9700 patches I'm still working on, and the multicast
filter removal is separate from the other changes.

Ethan

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

[Ethan Nelson-Moore]

On Mon, Jan 26, 2026 at 5:42 AM Simon Horman <horms@kernel.org> wrote:
> I would slightly lean towards splitting this patch up,
> say one for the multicast changes and removal of related #defines,
> and another for the remainder of the #define clean-up.
>
> But that notwithstanding this looks good to me.
>
> Reviewed-by: Simon Horman <horms@kernel.org>

Hi, Simon,

Thanks for your feedback.
Would it be appropriate for me to reuse your Reviewed-by tag for my
split patch? (The only other change is to use netdev_mc_empty instead
of checking if netdev_mc_count > 0.)

Ethan

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

[Simon Horman]

On Mon, Jan 26, 2026 at 09:37:48PM -0800, Ethan Nelson-Moore wrote:
> On Mon, Jan 26, 2026 at 5:42 AM Simon Horman <horms@kernel.org> wrote:
> > I would slightly lean towards splitting this patch up,
> > say one for the multicast changes and removal of related #defines,
> > and another for the remainder of the #define clean-up.
> >
> > But that notwithstanding this looks good to me.
> >
> > Reviewed-by: Simon Horman <horms@kernel.org>
> 
> Hi, Simon,
> 
> Thanks for your feedback.
> Would it be appropriate for me to reuse your Reviewed-by tag for my
> split patch? (The only other change is to use netdev_mc_empty instead
> of checking if netdev_mc_count > 0.)

Yes, that is fine.
Thanks for asking.