From: Rob Herring <robh@kernel.org>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Doug Anderson <dianders@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Frank Rowand <frowand.list@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux USB List <linux-usb@vger.kernel.org>,
Bastien Nocera <hadess@hadess.net>,
Stephen Boyd <swboyd@chromium.org>,
Ravi Chandra Sadineni <ravisadineni@chromium.org>,
Krzysztof Kozlowski <krzk@kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<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: Mon, 5 Oct 2020 14:36:45 -0500 [thread overview]
Message-ID: <CAL_Jsq+-kcDoFjp7a9ESa78Ar-ObLapXfuzn-WFNT-8rro_bJQ@mail.gmail.com> (raw)
In-Reply-To: <20201005191812.GB4135817@google.com>
On Mon, Oct 5, 2020 at 2:18 PM Matthias Kaehlcke <mka@chromium.org> wrote:
>
> On Mon, Oct 05, 2020 at 12:15:27PM -0400, Alan Stern wrote:
> > On Mon, Oct 05, 2020 at 09:06:55AM -0700, Matthias Kaehlcke wrote:
> > > On Sat, Oct 03, 2020 at 08:41:42AM -0400, Alan Stern wrote:
> > > > The decision to enable the power regulator at system startup would be
> > > > kernel policy, not a part of the DT description. But there ought to be
> > > > a standard way of recognizing which resource requirements of this sort
> > > > should be handled at startup. Then there could be a special module (in
> > > > the driver model core? -- that doesn't really seem appropriate) which
> > > > would search through the whole DT database for resources of this kind
> > > > and enable them.
> > >
> > > This might work for some cases that only have a single resource or multiple
> > > resources but no timing/sequencing requirements. For the more complex cases
> > > it would probably end up in something similar to the pwrseq series
> > > (https://lore.kernel.org/patchwork/project/lkml/list/?series=314989&state=%2A&archive=both),
> > > which was nack-ed by Rafael, Rob also expressed he didn't want to go
> > > down that road.
> > >
> > > It seems to me that initialization of the resources needs to be done by
> > > the/a driver for the device, which knows about the sequencing requirements.
> > > Potentially this could be done in a pre-probe function that you brought up
> > > earlier.
> >
> > One of the important points of my suggestion was that the resource init
> > should be done _outside_ of the device's driver, precisely because the
> > driver module might not even be loaded until the resources are set up
> > and the device is discovered.
> >
> > The conclusion is that we need to have code that is aware of some
> > detailed needs of a specific device but is not part of the device's
> > driver. I'm not sure what the best way to implement this would be.
>
> Wouldn't it be possible to load the module when the DT specifies that
> the device exists? For USB the kernel would need the VID/PID to identify
> the module, these could be extracted from the compatible string.
You don't even have to do that. Just add the MODULE_DEVICE_TABLE with
the compatible strings and module loading will just work once you walk
the USB bus in DT. Though probably you'd still need the VID/PID to
create the device.
Rob
next prev parent reply other threads:[~2020-10-05 19:37 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
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 [this message]
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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