linux-kernel - RE: [PATCH v3 2/6] usb:common Separated decoding functions from dwc3 driver.

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Date:   Tue, 05 Feb 2019 10:25:07 +0200
From:   Felipe Balbi <felipe.balbi@...ux.intel.com>
To:     Pawel Laszczak <pawell@...ence.com>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     "devicetree\@vger.kernel.org" <devicetree@...r.kernel.org>,
        "mark.rutland\@arm.com" <mark.rutland@....com>,
        "linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
        "hdegoede\@redhat.com" <hdegoede@...hat.com>,
        "heikki.krogerus\@linux.intel.com" <heikki.krogerus@...ux.intel.com>,
        "andy.shevchenko\@gmail.com" <andy.shevchenko@...il.com>,
        "robh+dt\@kernel.org" <robh+dt@...nel.org>,
        "rogerq\@ti.com" <rogerq@...com>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "jbergsagel\@ti.com" <jbergsagel@...com>,
        "nsekhar\@ti.com" <nsekhar@...com>, "nm\@ti.com" <nm@...com>,
        Suresh Punnoose <sureshp@...ence.com>,
        "peter.chen\@nxp.com" <peter.chen@....com>,
        Pawel Jez <pjez@...ence.com>, Rahul Kumar <kurahul@...ence.com>
Subject: RE: [PATCH v3 2/6] usb:common Separated decoding functions from dwc3 driver.


Hi,

Pawel Laszczak <pawell@...ence.com> writes:
>>On Thu, Jan 31, 2019 at 11:52:29AM +0000, Pawel Laszczak wrote:
>>> Patch moves some decoding functions from driver/usb/dwc3/debug.h driver
>>> to driver/usb/common/debug.c file. These moved functions include:
>>>     dwc3_decode_get_status
>>>     dwc3_decode_set_clear_feature
>>>     dwc3_decode_set_address
>>>     dwc3_decode_get_set_descriptor
>>>     dwc3_decode_get_configuration
>>>     dwc3_decode_set_configuration
>>>     dwc3_decode_get_intf
>>>     dwc3_decode_set_intf
>>>     dwc3_decode_synch_frame
>>>     dwc3_decode_set_sel
>>>     dwc3_decode_set_isoch_delay
>>>     dwc3_decode_ctrl
>>>
>>> These functions are used also in inroduced cdns3 driver.
>>>
>>> All functions prefixes were changed from dwc3 to usb.
>>
>>Ick, why?
>
> Because CDNS3 driver in one of the previous version had implemented very similar function as dwc3 and Felipe suggested that we should 
> make common file with these functions. He also suggested that this function also could be used on host side. 

right, host controllers can make use of Control transfer decoding.a

>>> Also, function's parameters has been extended according to the name
>>> of fields in standard SETUP packet.
>>> Additionally, patch adds usb_decode_ctrl function to
>>> include/linux/usb/ch9.h file.
>>
>>Why ch9.h?  It's not something that is specified in the spec, it's a
>>usb-specific thing :)
> Why not ?
>
> Similar as usb_state_string function from include/linux/usb/ch9.h which 
> " Returns human readable name for the state", the usb_decode_ctrl function 
> make the same but for standard USB request. 

right, I would say usb_state_string() should be moved elsewhere. ch9.h
is, really, just what's described in chapter 9 of the usb specification.

>>Also, the api for that function is not ok.  If you are going to make
>>this something that the whole kernel can call, you have to fix it up:
>>
>>> +/**
>>> + * usb_decode_ctrl - Returns human readable representation of control request.
>>> + * @str: buffer to return a human-readable representation of control request.
>>> + *       This buffer should have about 200 bytes.
>>
>>"about 200 bytes" is not very specific.
>>
>>Pass in the length so we know we don't overflow it.
>
> I didn't want to change to much this code, because it's not my code. 
> I'm not sure if I should ?

I have a patch for that, then you can start on top of it. I'll send it
soon after testing.

-- 
balbi

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