netdev - Re: [PATCH net-next 1/6] net: stmmac: add platform library

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Message-ID: <ZQDkR/YX2HPMKiF5@shell.armlinux.org.uk>
Date: Tue, 12 Sep 2023 23:20:55 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Simon Horman <horms@...nel.org>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	Alexei Starovoitov <ast@...nel.org>, bpf@...r.kernel.org,
	Daniel Borkmann <daniel@...earbox.net>,
	"David S. Miller" <davem@...emloft.net>,
	Emil Renner Berthing <kernel@...il.dk>,
	Eric Dumazet <edumazet@...gle.com>,
	Fabio Estevam <festevam@...il.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com,
	Maxime Coquelin <mcoquelin.stm32@...il.com>, netdev@...r.kernel.org,
	NXP Linux Team <linux-imx@....com>, Paolo Abeni <pabeni@...hat.com>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Samin Guo <samin.guo@...rfivetech.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>
Subject: Re: [PATCH net-next 1/6] net: stmmac: add platform library

On Tue, Sep 12, 2023 at 04:52:27PM +0200, Simon Horman wrote:
> On Mon, Sep 11, 2023 at 04:29:11PM +0100, Russell King (Oracle) wrote:
> > +	default:
> > +		return -ENOTSUPP;
> 
> Checkpatch seems to think that EOPNOTSUPP would be more appropriate
> as "ENOTSUPP is not a SUSV4 error code".

It needs to be an error code that clk_set_rate() below isn't going to
return - because if clk_set_rate() does return it, then the users are
going to end up issuing an incorrect error message to the user. I
suspect clk_set_rate() could quite legitimately return -EOPNOTSUPP
or -EINVAL.

Sadly, the CCF implementation of clk_set_rate() doesn't detail what
errors it could return, but it looks like -EBUSY, -EINVAL, or something
from pm_runtime_resume_and_get().

Interestingly, while looking at this, pm_runtime_resume_and_get() can
return '1' if e.g. rpm is disabled and the device is active. It looks
to me like CCF treats that as an error in multiple locations.

> > +	}
> > +
> > +	return clk_set_rate(tx_clk, rate);
> > +}
> > +EXPORT_SYMBOL_GPL(dwmac_set_tx_clk_gmii);

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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