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

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Simon Horman <horms@kernel.org>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	Alexei Starovoitov <ast@kernel.org>,
	bpf@vger.kernel.org, Daniel Borkmann <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	Emil Renner Berthing <kernel@esmil.dk>,
	Eric Dumazet <edumazet@google.com>,
	Fabio Estevam <festevam@gmail.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-stm32@st-md-mailman.stormreply.com,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	netdev@vger.kernel.org, NXP Linux Team <linux-imx@nxp.com>,
	Paolo Abeni <pabeni@redhat.com>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Samin Guo <samin.guo@starfivetech.com>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Shawn Guo <shawnguo@kernel.org>
Subject: Re: [PATCH net-next 1/6] net: stmmac: add platform library
Date: Tue, 12 Sep 2023 23:20:55 +0100	[thread overview]
Message-ID: <ZQDkR/YX2HPMKiF5@shell.armlinux.org.uk> (raw)
In-Reply-To: <20230912145227.GE401982@kernel.org>

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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