linux-kernel - Re: [PATCH] usb: host: Allow EHCI_OMAP to be built-in when USB

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Date:	Fri, 01 Jul 2016 11:15:21 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	Roger Quadros <rogerq@...com>
Cc:	stern@...land.harvard.edu, sre@...nel.org, peter.chen@....com,
	tony@...mide.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH] usb: host: Allow EHCI_OMAP to be built-in when USB_GADGET is 'm'


Hi,

Roger Quadros <rogerq@...com> writes:
>>>>> NOP_USB_XCEIV is used not only by gadget drivers but by
>>>>> host drivers as well e.g. EHCI_OMAP.
>>>>>
>>>>> commit 5a8d651a2bde ("usb: gadget: move gadget API functions to udc-core")
>>>>> made it so that NOP_USB_XCEIV can't be built-in if USB_GADGET is 'm'.
>>>>> But this prevents EHCI_OMAP to be built-in if USB_GADGET is 'm'.
>>>>>
>>>>> Fix this undesired behaviour by moving usb_gadget_vbus_connect/disconnect()
>>>>> to usb/gadget.h so that NOP_USB_XCEIV has no build dependency
>>>>> on USB_GADGET.
>>>>>
>>>>> Retain the original Kconfig behaviour i.e. NOP_USB_XCEIV is selected
>>>>> by drivers that need it.
>>>>
>>>> no, this is the wrong way to fix this. NOP _has_ a dependency on the
>>>> Gadget API if it calls Gadget API functions. Dependencies are proper.
>>>>
>>>> Maybe the reason for the problem is that we ended up adding far too much
>>>> code to phy-generic.c itself. Maybe it shouldn't know about clks and
>>>> interrupts. The original idea of that driver was to simply satisfy a
>>>> requirement to have a valid transceiver by some platforms. Maybe we
>>>> should fix that instead. Moving functions around to workaround a problem
>>>> is not the way to go, sorry.
>>>>
>>> OK but something that was working all these years is broken by your
>>> patch.
>>> Do you mind fixing it please? Or at least let me know how you want to
>>> get it fixed.
>> 
>> diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
>> index 2e710a4cca52..89fd095ca33d 100644
>> --- a/drivers/usb/host/Kconfig
>> +++ b/drivers/usb/host/Kconfig
>> @@ -180,7 +180,7 @@ config USB_EHCI_MXC
>>  config USB_EHCI_HCD_OMAP
>>         tristate "EHCI support for OMAP3 and later chips"
>>         depends on ARCH_OMAP
>> -       depends on NOP_USB_XCEIV
>> +       depends on USB_PHY
>>         default y
>>         ---help---
>>           Enables support for the on-chip EHCI controller on
>> 
>> 
> This doesn't fix the real problem. i.e. we can't have NFS root on pandaboard
> and omap5_uevm because network device is on USB EHCI, unless we have
> both USB_GADGET and NOP_USB_XCEVI built-in, which is not really that
> desirable.

Well, NOP calls a symbol that belongs to the Gadget API. So NOP cannot
be built-in if gadget API is a module. Satisfy the dependencies and
everything will work for you.

Don't get me wrong, I see what you mean; but you _are_ relying in a
driver that calls into the Gadget API. Consider if it was the other way
around: say NOP was calling something from usbcore for whatever reason
and MUSB depended on NOP. You wouldn't have MUSB built-in unless NOP and
usbcore were also built-in, right?

-- 
balbi

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