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From: Alan Stern <stern@rowland.harvard.edu>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Rob Herring <robh@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Frank Rowand <frowand.list@gmail.com>,
	linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
	Bastien Nocera <hadess@hadess.net>,
	Stephen Boyd <swboyd@chromium.org>,
	Douglas Anderson <dianders@chromium.org>,
	Ravi Chandra Sadineni <ravisadineni@chromium.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	devicetree@vger.kernel.org, Peter Chen <peter.chen@nxp.com>
Subject: Re: [PATCH v4 1/2] dt-bindings: usb: Add binding for discrete onboard USB hubs
Date: Tue, 29 Sep 2020 21:32:29 -0400	[thread overview]
Message-ID: <20200930013229.GB194665@rowland.harvard.edu> (raw)
In-Reply-To: <20200929220912.GF1621304@google.com>

On Tue, Sep 29, 2020 at 03:09:12PM -0700, Matthias Kaehlcke wrote:
> Hi Rob,
> 
> On Tue, Sep 29, 2020 at 03:17:01PM -0500, Rob Herring wrote:
> > As I said in prior version, this separate node and 'hub' phandle is not 
> > going to work. You are doing this because you want a platform driver for 
> > "realtek,rts5411". That may be convenient for Linux, but doesn't reflect 
> > the h/w.
> 
> I agree that the hardware representation isn't totally straightforward, however
> the description isn't limited to Linux:
> 
> - there is a single IC (like the Realtek RTS5411)
> - the IC may require several resources to be initialized in a certain way
>   - this may require executing hardware specific code by some driver, which
>     isn't a USB device driver
> - the IC can 'contain' multiple USB hub devices, which can be connected to
>   separate USB busses
> - the IC doesn't have a control bus, which somewhat resembles the
>   'simple-audio-amplifier' driver, which also registers a platform device
>   to initialize its resources
> 
> - to provide the functionality of powering down the hub conditionally during
>   system suspend the driver (whether it's a platform driver or something else)
>   needs know which USB (hub) devices correspond to it. This is a real world
>   problem, on hardware that might see wide distribution.
> 
> There were several attempts to solve this problem in the past, but none of them
> was accepted. So far Alan Stern seems to think the driver (not necessarily the
> binding as is) is a suitable solution, Greg KH also spent time reviewing it,
> without raising conceptual concerns. So it seems we have solution that would
> be generally landable from the USB side.
> 
> I understand that your goal is to keep the device tree sane, which I'm sure
> can be challenging. If you really can't be convinced that the binding might
> be acceptable in its current or similiar form then please offer guidance
> on possible alternatives which allow to achieve the same functionality.

You're really trying to represent this special IC in DT, right?  Maybe 
if you don't call it a "hub" but instead something that better reflects 
what it actually is and does, the description will be more palatable.

Alan Stern

  reply	other threads:[~2020-09-30  1:32 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-28 17:13 [PATCH v4 1/2] dt-bindings: usb: Add binding for discrete onboard USB hubs Matthias Kaehlcke
2020-09-28 17:13 ` [PATCH v4 2/2] USB: misc: Add onboard_usb_hub driver Matthias Kaehlcke
2020-09-28 18:47   ` Alan Stern
2020-09-29  1:43     ` Matthias Kaehlcke
2020-09-29 16:00       ` Alan Stern
2020-09-29 16:50         ` Matthias Kaehlcke
2020-09-28 22:03   ` Doug Anderson
2020-09-29  1:59     ` Matthias Kaehlcke
2020-09-28 22:13 ` [PATCH v4 1/2] dt-bindings: usb: Add binding for discrete onboard USB hubs Doug Anderson
2020-09-29  2:14   ` Matthias Kaehlcke
2020-09-29 20:17 ` Rob Herring
2020-09-29 22:09   ` Matthias Kaehlcke
2020-09-30  1:32     ` Alan Stern [this message]
2020-09-30 12:49       ` Matthias Kaehlcke
2020-09-30 14:44         ` Rob Herring
2020-09-30 15:28           ` Doug Anderson
2020-09-30 18:00             ` Doug Anderson
2020-09-30 19:19               ` Rob Herring
2020-10-01 21:39                 ` Matthias Kaehlcke
2020-09-30 19:19             ` Alan Stern
2020-09-30 20:20             ` Rob Herring
2020-10-01  1:24               ` Alan Stern
2020-10-01 21:54                 ` Matthias Kaehlcke
2020-10-02  1:21                   ` Alan Stern
2020-10-02 16:08                     ` Matthias Kaehlcke
2020-10-02 18:48                       ` Alan Stern
2020-10-02 17:08               ` Doug Anderson
2020-10-02 18:36                 ` Alan Stern
2020-10-02 22:58                   ` Rob Herring
2020-10-03 12:41                     ` Alan Stern
2020-10-05 16:06                       ` Matthias Kaehlcke
2020-10-05 16:15                         ` Alan Stern
2020-10-05 19:18                           ` Matthias Kaehlcke
2020-10-05 19:36                             ` Alan Stern
2020-10-05 19:59                               ` Rob Herring
2020-10-05 23:29                                 ` Matthias Kaehlcke
2020-10-05 19:36                             ` Rob Herring
2020-10-05 19:20                         ` Rob Herring
2020-10-02 22:28                 ` Rob Herring
2020-10-02 23:09                   ` Doug Anderson
2020-10-06  0:45                     ` Matthias Kaehlcke
2020-10-06 14:18                       ` Alan Stern
2020-10-06 16:59                         ` Matthias Kaehlcke
2020-10-06 17:15                           ` Alan Stern
2020-10-06 19:25                             ` Matthias Kaehlcke
2020-10-07  1:00                               ` Alan Stern
2020-10-07 16:03                                 ` Matthias Kaehlcke
2020-10-07 16:38                                   ` Alan Stern
2020-10-07 17:28                                     ` Matthias Kaehlcke
2020-10-07 19:25                                       ` Alan Stern
2020-10-07 19:42                                         ` Matthias Kaehlcke
2020-10-07 20:17                                           ` Alan Stern
2020-10-07 21:42                                             ` Matthias Kaehlcke
2020-10-08 14:09                                               ` Alan Stern
2020-10-09 23:13                                                 ` Matthias Kaehlcke

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