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Subject: Re: [PATCH net-next v2] net: qualcomm: rmnet: Allow partial updates
 of IFLA_FLAGS
To:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
        Sean Tranchetti <stranche@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210615232707.835258-1-bjorn.andersson@linaro.org>
From:   Alex Elder <elder@linaro.org>
Message-ID: <37f0f6f3-3a11-304f-4030-445e2bc578e6@linaro.org>
Date:   Tue, 15 Jun 2021 20:35:52 -0500
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On 6/15/21 6:27 PM, Bjorn Andersson wrote:
> The idiomatic way to handle the changelink flags/mask pair seems to be
> allow partial updates of the driver's link flags. In contrast the rmnet
> driver masks the incoming flags and then use that as the new flags.
> 
> Change the rmnet driver to follow the common scheme, before the
> introduction of IFLA_RMNET_FLAGS handling in iproute2 et al.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

KS was right, we want the same behavior in both newlink and changelink,
but aside from that, I like this a lot.

It looks good to me.

Reviewed-by: Alex Elder <elder@linaro.org>

> ---
> 
> Changes since v1:
> - Also do the masking dance on newlink, per Subash request
> - Add "net-next" to subject prefix
> 
>  drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
> index 8d51b0cb545c..27b1663c476e 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
> @@ -163,7 +163,8 @@ static int rmnet_newlink(struct net *src_net, struct net_device *dev,
>  		struct ifla_rmnet_flags *flags;
>  
>  		flags = nla_data(data[IFLA_RMNET_FLAGS]);
> -		data_format = flags->flags & flags->mask;
> +		data_format &= ~flags->mask;
> +		data_format |= flags->flags & flags->mask;
>  	}
>  
>  	netdev_dbg(dev, "data format [0x%08X]\n", data_format);
> @@ -336,7 +337,8 @@ static int rmnet_changelink(struct net_device *dev, struct nlattr *tb[],
>  
>  		old_data_format = port->data_format;
>  		flags = nla_data(data[IFLA_RMNET_FLAGS]);
> -		port->data_format = flags->flags & flags->mask;
> +		port->data_format &= ~flags->mask;
> +		port->data_format |= flags->flags & flags->mask;
>  
>  		if (rmnet_vnd_update_dev_mtu(port, real_dev)) {
>  			port->data_format = old_data_format;
>