From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2 2/2] USB: doc: Binding document for ehci-platform driver
Date: Thu, 25 Oct 2012 09:53:06 -0600 [thread overview]
Message-ID: <50896062.1090907@wwwdotorg.org> (raw)
In-Reply-To: <20121025102301.GA3469@breakpoint.cc>
On 10/25/2012 04:23 AM, Sebastian Andrzej Siewior wrote:
> On Wed, Oct 24, 2012 at 08:55:27AM -1000, Mitch Bradley wrote:
>>>> So by listing "usb-ehci" in its device ID table, a driver would
>>>> essentially be saying that it can handle _all_ USB EHCI controllers.
>>
>>
>> Actually, it means that the driver can handle at least USB EHCI
>> controllers that are 100% compatible with the EHCI spec (requiring
>> nothing extra). The driver might be able to handle almost-compatible
>> controllers, possibly with the help of additional properties.
>>
>> If a DT node lists "usb-ehci" as a "fallback", it's not guaranteed that
>> a given version of that driver will work, but it's worth a try in the
>> event that no more-specific driver is matched.
>
> Not sure fallback is a good term here. The of parses the compatible from left
> to right. If the device specific entry is not found (in the driver) then end
> up with usb-ehci. If we need a quirk later on we add the device specific entry
> to the driver (which will match before usb-ehci is found) and we could use
> this entry to apply the quirk. That way you can apply quirks without touch the
> firmware / device tree.
That's the theory on how the compatible values are used, but in
practice, each driver is tested against all the values in a node before
moving on to the next driver, so the (current kernel's implementation of
the) matching order is not what's needed to make that work.
next prev parent reply other threads:[~2012-10-25 15:53 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-20 22:10 [PATCH v2 0/2] Update ehci-platform driver to support devicetree Tony Prisk
2012-10-20 22:10 ` [PATCH v2 1/2] USB: Update EHCI-platform driver to devicetree Tony Prisk
2012-10-21 2:02 ` Alan Stern
2012-10-20 22:10 ` [PATCH v2 2/2] USB: doc: Binding document for ehci-platform driver Tony Prisk
2012-10-21 17:34 ` Florian Fainelli
2012-10-22 16:07 ` Stephen Warren
2012-10-22 17:34 ` Alan Stern
2012-10-22 17:48 ` Stephen Warren
2012-10-22 19:00 ` Alan Stern
2012-10-22 22:10 ` Stephen Warren
2012-10-23 14:10 ` Alan Stern
2012-10-23 16:15 ` Stephen Warren
2012-10-23 17:59 ` Alan Stern
2012-10-23 18:47 ` Stephen Warren
2012-10-23 19:33 ` Alan Stern
2012-10-23 20:06 ` Rob Herring
2012-10-24 14:57 ` Alan Stern
2012-10-24 15:26 ` Sebastian Andrzej Siewior
2012-10-24 16:16 ` Stephen Warren
2012-10-24 16:36 ` Florian Fainelli
2012-10-24 16:38 ` Alan Stern
2012-10-24 16:44 ` Florian Fainelli
2012-10-24 18:04 ` Alan Stern
2012-10-24 18:18 ` Florian Fainelli
2012-10-24 16:45 ` Stephen Warren
2012-10-24 17:46 ` Alan Stern
2012-10-24 18:09 ` Stephen Warren
2012-10-24 18:55 ` Mitch Bradley
2012-10-24 19:30 ` Alan Stern
2012-10-25 10:23 ` Sebastian Andrzej Siewior
2012-10-25 14:36 ` Alan Stern
2012-10-26 8:02 ` Sebastian Andrzej Siewior
2012-10-26 14:54 ` Alan Stern
2012-10-25 15:53 ` Stephen Warren [this message]
2012-10-24 19:41 ` Alan Stern
2012-10-24 16:44 ` Alan Stern
2012-10-24 16:48 ` Stephen Warren
2012-10-24 17:42 ` Rob Herring
2012-10-24 17:57 ` Alan Stern
2012-10-24 16:28 ` Stephen Warren
2012-10-24 16:54 ` Alan Stern
2012-10-24 17:37 ` Florian Fainelli
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