Message-ID: <4FDF4543.6090009@wwwdotorg.org>
Date: Mon, 18 Jun 2012 09:12:03 -0600
From: Stephen Warren <swarren@wwwdotorg.org>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1
MIME-Version: 1.0
To: Roland Stigge <stigge@antcom.de>
CC: cjb@laptop.org, grant.likely@secretlab.ca, rob.herring@calxeda.com,
        rmk+kernel@arm.linux.org.uk, ulf.hansson@stericsson.com,
        linus.walleij@linaro.org, linux-mmc@vger.kernel.org,
        linux-kernel@vger.kernel.org, aletes.xgr@gmail.com,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] gpio: of_get_named_gpio_flags() return -EPROBE_DEFER
 if GPIO not yet available
References: <1339927893-8842-1-git-send-email-stigge@antcom.de> <4FDE8D27.6030508@wwwdotorg.org> <4FDEF293.9080305@antcom.de> <4FDF403E.9090302@wwwdotorg.org> <4FDF4461.60707@antcom.de>
In-Reply-To: <4FDF4461.60707@antcom.de>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1963
Lines: 36

On 06/18/2012 09:08 AM, Roland Stigge wrote:
> On 06/18/2012 04:50 PM, Stephen Warren wrote:
>>> Can you please tell in which way the patch breaks those drivers?
>>> However, I can see that those drivers solved the same problem in a
>>> different way (deferring of_get_named_gpio(), via the sound init()). So
>>> they could be adjusted to take advantage of new -EPROBE_DEFER.
>>
>> The drivers I mentioned test the return code of of_get_named_gpio() to
>> see if it's -ENODEV, which means that DT property for that GPIO exists
>> but the driver for it isn't available yet, so the property can't be
>> parsed. In this case, the sound drivers defer their own probe. If
>> of_get_named_gpio() is modified to return -EPROBE_DEFER directly, then
>> it won't be returning -ENODEV, and hence the sound drivers' check for
>> -ENODEV won't fire, and hence the sound drivers will just continue their
>> probe assuming that the particular GPIOs are not present on the board
>> (since they are all optional, so anything other than an explicit
>> deferral error from of_get_named_gpio() is not treated as an error).
>> This will break sound on those platforms.
> 
> Thanks for the hint! I previously also suspected sth. like this but
> didn't find it in v3.5-rc3. In broonie's sound.git for-next, I now
> finally found it.
> 
> Should be easy to fix (replacing the if (... == -ENODEV) to -EPROBE_DEFER.
> 
> Will you provide patches as signalled, of should I? Which branch would
> be the correct one to build on top?

I'm happy either way. It'd probably be best to roll the change into your
patch/series so you can manage all the dependencies in one series, but
if you can't for some reason, I'm happy to provide a patch for this.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/