Re: [PATCH] net: usb: pegasus: ignore the return value from set_registers();

On 8/14/21 2:24 AM, Jakub Kicinski wrote:

On Thu, 12 Aug 2021 11:23:51 +0300 Petko Manolov wrote:

quoted

The return value need to be either ignored or acted upon, otherwise 'deadstore'
clang check would yell at us.  I think it's better to just ignore what this
particular call of set_registers() returns.  The adapter defaults are sane and
it would be operational even if the register write fail.

Signed-off-by: Petko Manolov <redacted>
---
 drivers/net/usb/pegasus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c
index 652e9fcf0b77..49cfc720d78f 100644
--- a/drivers/net/usb/pegasus.c
+++ b/drivers/net/usb/pegasus.c

@@ -433,7 +433,7 @@ static int enable_net_traffic(struct net_device *dev, struct usb_device *usb)
 	data[2] = loopback ? 0x09 : 0x01;
 
 	memcpy(pegasus->eth_regs, data, sizeof(data));
-	ret = set_registers(pegasus, EthCtrl0, 3, data);
+	set_registers(pegasus, EthCtrl0, 3, data);
 
 	if (usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS ||
 	    usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS2 ||

This one is not added by the recent changes as I initially thought,
the driver has always checked this return value. The recent changes
did this:

         ret = set_registers(pegasus, EthCtrl0, 3, data);
  
         if (usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS ||
             usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS2 ||
             usb_dev_id[pegasus->dev_index].vendor == VENDOR_DLINK) {
                 u16 auxmode;
-               read_mii_word(pegasus, 0, 0x1b, &auxmode);
+               ret = read_mii_word(pegasus, 0, 0x1b, &auxmode);
+               if (ret < 0)
+                       goto fail;
                 auxmode |= 4;
                 write_mii_word(pegasus, 0, 0x1b, &auxmode);
         }
  
+       return 0;
+fail:
+       netif_dbg(pegasus, drv, pegasus->net, "%s failed\n", __func__);
         return ret;
}

now the return value of set_registeres() is ignored.

Seems like  a better fix would be to bring back the error checking,
why not?

Please remember to add a fixes tag.

Hi, Jakub!

I've suggested to handle this error, but Petko said that device won't 
stop working, it will just get in non-optimal state.

https://lore.kernel.org/lkml/YRF1t5kx6hTrv5LC@carbon/ (local)


With regards,
Pavel Skripkin