From: Valentine Barshak <vbarshak@ru•mvista.com>
To: Segher Boessenkool <segher@kernel•crashing.org>
Cc: linuxppc-dev@ozlabs•org, linux-usb-devel@lists•sourceforge.net
Subject: Re: [PATCH 2/3] usb: ehci-ppc-of dts bindings.
Date: Wed, 19 Sep 2007 20:55:02 +0400 [thread overview]
Message-ID: <46F15466.6000803@ru.mvista.com> (raw)
In-Reply-To: <d0e5786123822b4d178932d9048f6a22@kernel.crashing.org>
Segher Boessenkool wrote:
>>>> + Required properties:
>>>> + - device_type : should be "usb".
>>> No device_type please. The published USB binding doesn't define
>>> one on purpose.
>>
>> Could you please, explain why?
>> Sorry, I don't think I get the concept of device description here.
>
> "device_type" is meant to be used only by OF for determining the OF
> programming model for a device. No such thing has been defined for
> USB busses, so the USB binding does not define a "device_type" either.
>
> Nothing in a flat device tree should ever define a device_type, except
> perhaps for compatibility with legacy kernel code.
>
>>>> + - compatible : should be "ehci".
>>> Just "ehci" isn't enough -- compare to OHCI, which is the name for
>>> a kind of USB host controller as well as for a kind of Firewire
>>> host controller.
>>
>> Actually, I though device type="usb" + compatible="ehci" would be enough.
>
> "compatible" values are their own namespace, you should in principle
> be able to find a driver for a device with them without having to look
> at other properties.
>
>>> Maybe "usb-ehci" is best -- can anyone think of a better name?
>>
>> Again, why not type="usb", compatible="ehci"?
>
> Because an OF client (i.e., the Linux kernel) is not supposed to use
> "device_type" at all for its own driver matching.
>
>>>> + - interrupts : <a b> where a is the interrupt number and b is a
>>>> + field that represents an encoding of the sense and level
>>>> + information for the interrupt.
>>> This is incorrect; not all interrupt domains use two cells, and
>>> not all that do have this meaning for those cells.
>>
>> Well, this was just copied from other descriptions in
>> Documentation/powerpc/booting-without-of.txt
>> Do we need to fix them all?
>
> Sounds like it, yes.
>
>>>> + If device registers are implemented in big endian mode, the device
>>>> + node should have "big-endian" property.
>>>> + If controller implementation operates with big endian descriptors,
>>>> + compatible should also have "ehci-be-desc"
>>> Ah, I understand what this is about, finally.
>>> Don't put this in "compatible"; instead, do a "big-endian-descriptors"
>>> property similar to the "big-endian" property. That last one should
>>> maybe be "big-endian-registers" here then, to avoid confusion.
>>> Or make "big-endian" mean both big-endian registers *and* big-endian
>>> descriptors.
>>
>> But doesn't "big-endian" property actually mean "big-endian-registers"?
>> Do we have to overload property meaning in this case?
>
> It doesn't *have* a standard meaning, it is defined per device binding
> that uses it. Just make it mean whatever is most logical for this
> device.
>
>>> I have no opinion which is best; it depends on what configurations
>>> actually exist, and how popular those are.
>
>
> Segher
>
OK, thanks a lot for the explanations.
I'll modify the code.
I think may be usb-ohci compatible values should be made properties as well,
so that both drivers follow the same rules.
Thanks,
Valentine.
next prev parent reply other threads:[~2007-09-19 16:56 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-17 12:50 [PATCH 0/3] usb: ehci ppc device-tree-aware driver Valentine Barshak
2007-09-17 12:55 ` [PATCH 1/3] usb: add device-tree-aware ehci driver Valentine Barshak
2007-09-17 13:00 ` [PATCH 2/3] usb: ehci-ppc-of dts bindings Valentine Barshak
2007-09-19 0:25 ` Segher Boessenkool
2007-09-19 13:52 ` Valentine Barshak
2007-09-19 16:50 ` Segher Boessenkool
2007-09-19 16:55 ` Valentine Barshak [this message]
2007-09-24 19:32 ` [linux-usb-devel] " Valentine Barshak
2007-09-20 0:52 ` David Gibson
2007-09-24 21:40 ` Segher Boessenkool
2007-09-17 13:28 ` [PATCH 1/3] usb: add device-tree-aware ehci driver Stephen Rothwell
2007-09-17 14:00 ` Josh Boyer
2007-09-17 18:17 ` Valentine Barshak
2007-09-18 4:26 ` Stephen Rothwell
2007-09-18 5:39 ` David Gibson
2007-09-17 18:18 ` Valentine Barshak
2007-09-17 13:02 ` [PATCH 3/3] Add PowerPC 440EPx Sequoia ehci dts entry Valentine Barshak
2007-09-22 23:00 ` [PATCH 0/3] usb: ehci ppc device-tree-aware driver Hollis Blanchard
2007-09-24 10:33 ` Valentine Barshak
2007-10-08 18:15 ` Jerone Young
2007-10-08 18:18 ` Valentine Barshak
2007-10-08 18:22 ` Valentine Barshak
-- strict thread matches above, loose matches on Subject: below --
2007-09-24 19:25 Valentine Barshak
2007-09-24 19:27 ` [PATCH 2/3] usb: ehci-ppc-of dts bindings Valentine Barshak
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