linux-kernel - Re: [alsa-devel] [RFC PATCH] ASoC: wm8731: let codec to manage clock by itself

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 3 Feb 2015 17:17:33 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Mark Brown <broonie@...nel.org>,
	Manuel Lauss <manuel.lauss@...il.com>,
	alsa-devel <alsa-devel@...a-project.org>,
	Richard Purdie <richard@...nedhand.com>,
	patches@...nsource.wolfsonmicro.com,
	LKML <linux-kernel@...r.kernel.org>, linux-sound@...r.kernel.org,
	Manuel Lauss <manuel.lauss@...glemail.com>,
	Bo Shen <voice.shen@...el.com>,
	linux-arm-kernel@...ts.infradead.org,
	Liam Girdwood <lrg@...mlogic.co.uk>
Subject: Re: [alsa-devel] [RFC PATCH] ASoC: wm8731: let codec to manage clock
 by itself

On Tue, Feb 03, 2015 at 05:53:48PM +0100, Lars-Peter Clausen wrote:
> On 02/03/2015 01:44 PM, Mark Brown wrote:
> >On Tue, Feb 03, 2015 at 08:54:57AM +0100, Manuel Lauss wrote:
> >
> >>+    wm8731->mclk = devm_clk_get(&spi->dev, "mclk");
> >>+    if (IS_ERR(wm8731->mclk)) {
> >>+        wm8731->mclk = NULL;
> >>+        dev_warn(&spi->dev, "assuming static MCLK\n");
> >>+    }
> >
> >This is broken for both deferred probe and in the case where the clock
> >API genuinely returns a NULL clock.  Other than that it's the kind of
> >thing that we've done for some other drivers, though it's not good to
> >have to do this.  Check them for correct behaviour.
> 
> Ideally we'd introduce a {devm_}clk_get_optional(), with the same semantics
> as gpiod_get_optional(), which handles the finer details of differentiating
> between clock specified, but not yet probed, clock specified, but
> incorrectly and no clock specified, so this doesn't have to be done over and
> over by each driver.

No, we don't need to.  It clk_get() already knows this distinction, and
it appropriately returns -ENOENT vs -EPROBE_DEFER according to whether
there's a clock specified in DT or not.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/