netdev - Re: [RFCv8 PATCH net-next 00/55] net: extend the type of netdev_features

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Date:   Mon, 28 Nov 2022 16:51:27 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     "shenjian (K)" <shenjian15@...wei.com>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        davem@...emloft.net, kuba@...nel.org, ecree.xilinx@...il.com,
        andrew@...n.ch, hkallweit1@...il.com, saeed@...nel.org,
        leon@...nel.org, netdev@...r.kernel.org, linuxarm@...wei.com
Subject: Re: [RFCv8 PATCH net-next 00/55] net: extend the type of netdev_features_t to bitmap

From: "shenjian (K)" <shenjian15@...wei.com>
Date: Mon, 28 Nov 2022 23:22:28 +0800

> 2022/11/25 23:44, Alexander Lobakin:
> > From: Jian Shen <shenjian15@...wei.com>
> > Date: Sun, 18 Sep 2022 09:42:41 +0000
> >
> >> For the prototype of netdev_features_t is u64, and the number
> >> of netdevice feature bits is 64 now. So there is no space to
> >> introduce new feature bit.
> >>
> >> This patchset try to solve it by change the prototype of
> >> netdev_features_t from u64 to structure below:
> >> 	typedef struct {
> >> 		DECLARE_BITMAP(bits, NETDEV_FEATURE_COUNT);
> >> 	} netdev_features_t;
> >>
> >> With this change, it's necessary to introduce a set of bitmap
> >> operation helpers for netdev features. [patch 1]
> > Hey,
> >
> > what's the current status, how's going?
> >
> > [...]
> Hi, Alexander
> 
> Sorry to reply late, I'm still working on this, dealing with split the 
> patchset.

Hey, no worries. Just curious as I believe lots of new features are
waiting for new bits to be available :D

> 
> Btw, could you kindly review this V8 set? I have adjusted the protocol 
> of many interfaces and helpers,

I'll try to find some time to review it this week, will see.

> to avoiding return or pass data large than 64bits. Hope to get more 

Yes, I'd prefer to not pass more than 64 bits in one function
argument, which means functions operating with netdev_features_t
must start take pointers. Otherwise, with passing netdev_features_t
directly as a struct, the very first newly added feature will do
8 -> 16 bytes on the stack per argument, boom.

> opinions.
> 
> Thanks!
> 
> Jian
> >> -- 
> >> 2.33.0
> > Thanks,
> > Olek

Thanks,
Olek