linux-kernel - Re: [PATCH net-next v3 08/12] net: stmmac: Pass stmmac

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Message-ID: <20230410212422.2rztlqspw5vjtb4d@halaney-x13s>
Date:   Mon, 10 Apr 2023 16:24:22 -0500
From:   Andrew Halaney <ahalaney@...hat.com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     linux-kernel@...r.kernel.org, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org,
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Subject: Re: [PATCH net-next v3 08/12] net: stmmac: Pass stmmac_priv in some
 callbacks

On Fri, Apr 07, 2023 at 12:34:53PM -0500, Andrew Halaney wrote:
> On Sat, Apr 01, 2023 at 05:06:21PM +0200, Simon Horman wrote:
> > On Fri, Mar 31, 2023 at 04:45:45PM -0500, Andrew Halaney wrote:
> > > Passing stmmac_priv to some of the callbacks allows hwif implementations
> > > to grab some data that platforms can customize. Adjust the callbacks
> > > accordingly in preparation of such a platform customization.
> > > 
> > > Signed-off-by: Andrew Halaney <ahalaney@...hat.com>
> > 
> > ...
> > 
> > >  #define stmmac_reset(__priv, __args...) \
> > > @@ -223,59 +240,59 @@ struct stmmac_dma_ops {
> > >  #define stmmac_dma_init(__priv, __args...) \
> > >  	stmmac_do_void_callback(__priv, dma, init, __args)
> > >  #define stmmac_init_chan(__priv, __args...) \
> > > -	stmmac_do_void_callback(__priv, dma, init_chan, __args)
> > > +	stmmac_do_void_callback(__priv, dma, init_chan, __priv, __args)
> > 
> > Hi Andrew,
> > 
> > Rather than maintaining these macros can we just get rid of them?
> > I'd be surprised if things aren't nicer with functions in their place [1].
> > 
> > f.e., we now have (__priv, ..., __priv, ...) due to a generalisation
> >       that seems to take a lot more than it gives.
> > 
> > [1] https://lore.kernel.org/linux-arm-kernel/ZBst1SzcIS4j+t46@corigine.com/
> > 
> 
> Thanks for the pointer. I think that makes sense, I'll take that
> approach for these functions (and maybe in a follow-up series I'll
> tackle all of them just because the lack of consistency will eat me up).
> 

I tried taking this approach for a spin, and I'm not so sure about it
now!

1. Implementing the functions as static inline requires us to know
   about stmmac_priv, but that's getting into circular dependency land
2. You could define them in hwif.c, but then they're not inlined
3. There's still a good bit of boilerplate that's repeated all over
   with the approach. Ignoring 1 above, you get something like this:

static inline int stmmac_init_chan(struct stmmac_priv *priv,
				   void __iomem *ioaddr,
				   struct stmmac_dma_cfg *dma_cfg, u32 chan)
{
	if (priv->hw->dma && priv->hw->dma->init_chan) {
		priv->hw->dma->init_chan(priv, ioaddr, dma_cfg, chan);
		return 0;
	}
	return -EINVAL;
}

that is then repeated for every function... which is making me actually
appreciate the macros some for reducing boilerplate.

Am I suffering from a case of holiday brain, and 1-3 above are silly
points with obvious answers, or do they make you reconsider continuing
with the current approach in hwif.h?

Thanks,
Andrew