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From: Alan Stern <stern@rowland.harvard.edu>
To: Michael Grzeschik <mgr@pengutronix.de>
Cc: linux-usb@vger.kernel.org, gregkh@linuxfoundation.org,
	kernel@pengutronix.de
Subject: Re: [PATCH v2] usb: hub: port: add sysfs entry to switch port power
Date: Thu, 2 Jun 2022 20:25:09 -0400	[thread overview]
Message-ID: <YplU5dHLZdQDGMh1@rowland.harvard.edu> (raw)
In-Reply-To: <20220602213454.GC26638@pengutronix.de>

On Thu, Jun 02, 2022 at 11:34:54PM +0200, Michael Grzeschik wrote:
> On Thu, Jun 02, 2022 at 03:16:27PM -0400, Alan Stern wrote:
> > On Thu, Jun 02, 2022 at 04:59:18PM +0200, Michael Grzeschik wrote:
> > > Because of that; I am currently curious if we just should rename that
> > > property to something more generic like "enable" or "disable". So that
> > > as the real vbus power switching is missing, the hubs port switching
> > > does still function like intended.
> > 
> > That makes sense.  But the question arises, does this patch really do what
> > you want?
> > 
> > The patch description talks about the need to disable devices or
> > re-enumerate them.  You can disable a device right now by writing -1 to
> > the bConfigurationValue sysfs file, and you can force a device to be
> > re-enumerated by resetting it (using the USBDEVFS_RESET usbfs ioctl).
> > 
> > About the only thing you can't currently do is actually turn off power to
> > the port.  This patch will allow users to do that, but only if the hub
> > supports power switching.
> > 
> > (Okay, there's one other thing: The patch also allows users to disable a
> > port, so that devices plugged into that port get ignored.  Maybe that's
> > what you really had in mind...?)
> 
> Yes, that is what I had in mind. If you agree, I would still keep the
> name "port_power" since it is the main function, but skip the
> hub_is_port_power_switchable check.

I favor the more generic name.  "disable" will be more understandable for 
users than "port_power", if the file doesn't actually control the bus 
power.

Alan Stern

      reply	other threads:[~2022-06-03  0:25 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-02  1:27 [PATCH v2] usb: hub: port: add sysfs entry to switch port power Michael Grzeschik
2022-06-02 14:39 ` Alan Stern
2022-06-02 14:59   ` Michael Grzeschik
2022-06-02 19:16     ` Alan Stern
2022-06-02 21:34       ` Michael Grzeschik
2022-06-03  0:25         ` Alan Stern [this message]

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