Re: [PATCH 3/5] usb: gadget: gmidi: remove bus powered requirement on bmAttributes

From: Felipe Balbi
Date: Tue Mar 08 2016 - 05:35:44 EST


Krzysztof Opasiak <k.opasiak@xxxxxxxxxxx> writes:
> [ text/plain ]
> On 03/08/2016 08:43 AM, Felipe Balbi wrote:
> (...)
>>>>> This is necessary because this driver is actually wrong in which is
>>>>> asking for the host to power itself. This is not specified on USB-MIDI
>>>>> specification, neither makes any sense since this configuration is
>>>>> device specific.
>>>>> What is your suggestion to make it configurable? Maybe at compile-time?
>>>>> I really don't know what is the best solution if this is not something
>>>>> you like it.
>>>> well, you could use our configfs-based gadget interface. You don't
>>>> really need to use gmidi.ko at all. In fact, we wanna do away with any
>>>> static modules and rely only on configfs. If configfs doesn't let you
>>>> change what you want/need, then we can talk about adding support for
>>>> those.
>>>> bMaxPower and bmAttributes sound like good things to have configurable
>>>> over configfs but beware of what the USB specification says about them,
>>>> we cannot let users violate the spec by passing bogus values on these
>>>> fields.
>>> I agree that we should move to configfs, but the truth is that these
>>> legacy devices are still useful. They just do one thing, mostly, but
>> yes, they are useful as they are. They don't need to be changed to be
>> useful. Plus, you can have a gadget built with configfs that does only
>> one thing. And you can do that with a simple shell script.
>>> its easy and simple to setup and use. So I think before we have some
>> so is configfs.
>>> sort of preset library of configfs-based gadget drivers, we still need
>>> these modules.
>> there is already a library called libusbg.
> As libusbg itself is a little bit dead there is a fork called
> libusbgx[1] and it is still active;)
> It already has support for f_midi so it is ready to use.

heh, seems like usb libraries tend to get forked with an 'x' appended to
their name. But thanks for the note.


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