RE: [PATCH v6 1/6] clk: Add of_clk_get_by_name_optional() function

From: Phil Edworthy <phil.edworthy@renesas.com>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Stephen Boyd <sboyd@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Russell King <linux@armlinux.org.uk>,
	"linux-clk@vger.kernel.org" <linux-clk@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-renesas-soc@vger.kernel.org" 
	<linux-renesas-soc@vger.kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: RE: [PATCH v6 1/6] clk: Add of_clk_get_by_name_optional() function
Date: Mon, 19 Nov 2018 10:41:42 +0000	[thread overview]
Message-ID: <TY1PR01MB17697C2C8BCE98009EBDECF7F5D80@TY1PR01MB1769.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <20181116161122.hhvslbzdujxpk3up@pengutronix.de>

Hi Uwe,

On 16 November 2018 16:11 Uwe Kleine-König wrote:
> On Fri, Nov 16, 2018 at 05:01:28PM +0100, Uwe Kleine-König wrote:
> > Other than that I think the patch is fine
> 
> Thinking again, I wonder why not just do:
> 
> static inline struct clk *clk_get_optional(struct device *dev, const char *id) {
> 	struct clk *c = clk_get(dev, id);
> 
> 	if (c == ERR_PTR(-ENOENT))
> 		return NULL;
> 	else
> 		return c;
> }

Unfortunately, underneath this __of_clk_get_by_name() returns -EINVAL
when looking for a named clock, and the "clock-names" OF property can't
be found or the name is not in that prop. This is because the index
returned by of_property_match_string() will be an error code and is then
currently always passed to __of_clk_get().

If, as you said, I split the patches into one that fixes the error code, and then
adds clk_get_optional() like above, it will make more sense.

btw, do we need to add of_clk_get_by_name_optional()? I only added it as a
counterpart to of_clk_get_by_name(), but it may not be needed.

Thanks
Phil