linux-kernel - Re: [PATCH 3/3] watchdog: omap

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Message-ID: <4FC5D21F.2030702@ti.com>
Date:	Wed, 30 May 2012 09:54:07 +0200
From:	"Cousson, Benoit" <b-cousson@...com>
To:	Xiao Jiang <jgq516@...il.com>
CC:	Jon Hunter <jon-hunter@...com>, <linux@....linux.org.uk>,
	<rob.herring@...xeda.com>, <grant.likely@...retlab.ca>,
	<rnayak@...com>, <tony@...mide.com>, <wim@...ana.be>,
	<devicetree-discuss@...ts.ozlabs.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-watchdog@...r.kernel.org>
Subject: Re: [PATCH 3/3] watchdog: omap_wdt: add device tree support

On 5/30/2012 5:18 AM, Xiao Jiang wrote:
> Jon Hunter wrote:
>> On 05/25/2012 05:42 AM, jgq516@...il.com wrote:
>>> From: Xiao Jiang <jgq516@...il.com>
>>>
>>> Add device table for omap_wdt to support dt.
>>>
>>> Signed-off-by: Xiao Jiang <jgq516@...il.com>
>>> ---
>>> drivers/watchdog/omap_wdt.c | 8 ++++++++
>>> 1 files changed, 8 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/watchdog/omap_wdt.c b/drivers/watchdog/omap_wdt.c
>>> index 8285d65..d98c615 100644
>>> --- a/drivers/watchdog/omap_wdt.c
>>> +++ b/drivers/watchdog/omap_wdt.c
>>> @@ -430,6 +430,13 @@ static int omap_wdt_resume(struct
>>> platform_device *pdev)
>>> #define omap_wdt_resume NULL
>>> #endif
>>>
>>> +static const struct of_device_id omap_wdt_of_match[] = {
>>> + { .compatible = "ti,omap3-wdt", },
>>> + { .compatible = "ti,omap4-wdt", },

If there is no difference between the OMAP3 and the OMAP4 WDT IP, just 
add one entry "ti,omap3-wdt". And then in the OMAP4 DTS you will just 
put : compatible = "ti,omap3-wdt"; or compatible =  "ti,omap4-wdt", 
"ti,omap3-wdt";
I'm still a little bit confused about the real need for the 
"ti,omap4-wdt: entry, but it seems to be the way to do it in PPC.

>>> + {},
>>> +};
>>> +MODULE_DEVICE_TABLE(of, omap_wdt_of_match);
>>> +
>>> static struct platform_driver omap_wdt_driver = {
>>> .probe = omap_wdt_probe,
>>> .remove = __devexit_p(omap_wdt_remove),
>>> @@ -439,6 +446,7 @@ static struct platform_driver omap_wdt_driver = {
>>> .driver = {
>>> .owner = THIS_MODULE,
>>> .name = "omap_wdt",
>>> + .of_match_table = omap_wdt_of_match,
>>> },
>>> };
>>>
>>
>> I think we need to add some code to the probe function that calls
>> of_match_device() and ensures we find a match. For example ...
>>
>> if (of_have_populated_dt())
>> if (!of_match_device(omap_wdt_of_match, &pdev->dev))
>> return -EINVAL;
>>
> Will add it in v2, thanks for suggestion.

No, in fact this is not needed. We need that mainly when several 
instances can match the same driver and thus we select the proper one 
using the of_match_device. Otherwise, just check is the device_node is 
there.

In that case, the driver does not even care about any DT node so there 
is no need to add extra code for that. Keep it simple.

Regards,
Benoit
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