linux-kernel - Re: [EXTERNAL] Re: [PATCH rdma-next 1/1] RDMA/mana

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Message-ID: <20260113140747.GB179508@unreal>
Date: Tue, 13 Jan 2026 16:07:47 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Konstantin Taranov <kotaranov@...rosoft.com>
Cc: Konstantin Taranov <kotaranov@...ux.microsoft.com>,
	Shiraz Saleem <shirazsaleem@...rosoft.com>,
	Long Li <longli@...rosoft.com>, "jgg@...pe.ca" <jgg@...pe.ca>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [EXTERNAL] Re: [PATCH rdma-next 1/1] RDMA/mana_ib: take CQ type
 from the device type

On Tue, Jan 13, 2026 at 12:27:57PM +0000, Konstantin Taranov wrote:
> > >
> > > -		is_rnic_cq = !!(ucmd.flags & MANA_IB_CREATE_RNIC_CQ);
> > 
> > You need to add code which prohibits future use of this BIT(0) in ucmd.flags
> > for backward compatibility and maybe delete MANA_IB_CREATE_RNIC_CQ
> > from UAPI too.
> > 
> > Thanks
> > 
> 
> Hi Leon. I thought that my proposed change is backward and forward compatible.
> If I add code that prohibits this flag, then the older rdma-core will fail to create CQ,
> as it sets this flag. Add rdma-core should set the flag to support older kernels.
> 
> So, the current solution is as follows:
> rdma-core always sends the flag. The kernels without this patch still use this flag.
> Newer kernels just ignore the flag and create the CQ according to the client.
> It is not fully possible to retire this flag now, as we want to be backwards compatible and
> support older kernels and older rdma-core.
> Or did you mean something else? Or do I miss something?

There needs to be a way to document in the code that this bit is reserved and
must not be used.

Thanks

> 
> Thanks