From: Ingo Rohloff <ingo.rohloff@lauterbach.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org, linux-hotplug@vger.kernel.org
Subject: Re: [PATCH] USB: usbfs: Suppress emission of uevents for interfaces handled via usbfs
Date: Thu, 10 Oct 2019 12:53:08 +0000 [thread overview]
Message-ID: <20191010130913.5af35519@ingpc3.intern.lauterbach.com> (raw)
In-Reply-To: <20191010102411.GA541845@kroah.com>
Hello Greg
> > + else {
> > + /* suppress uevents for devices handled by usbfs */
> > + dev_set_uevent_suppress(&intf->dev, 1);
> > err = usb_driver_claim_interface(&usbfs_driver, intf, ps);
> > + if (err != 0)
> > + dev_set_uevent_suppress(&intf->dev, 0);
> Did checkpatch let this go through? Shouldn't that be:
> if (err)
I actually wanted it the way it is, but it really might not be the best option.
Let me explain:
The main goal was to suppress bind/unbind uevents produced by libusb
or any other user space program which calls
ioctl USBDEVFS_CLAIMINTERFACE/USBDEVFS_RELEASEINTERFACE .
Now I can suppress uevents produced by usb_driver_claim_interface
with the code above.
But I was not sure how to handle the call to usb_driver_release_interface
from devio.c/releaseintf()
The strategy I used was:
1) Set suppression of uevents when user space program tries to claim interface
2) If claiming the interface works, then KEEP uevents suppressed,
otherwise undo suppression.
That's why its "if err !=0"; error happened => undo suppression.
3) When interface is released make sure suppression is undone AFTER unbinding the driver.
Thinking about your comment: It might be better + simpler to just use
1) Suppress uevents when calling usb_driver_claim_interface. Undo suppression right after the call.
2) Suppress uevents when calling usb_driver_release_interface. Undo suppression right after the call.
The main semantic problem I do not know about:
Is it correct to modify uevent suppression of an USB interface device
even if it CANNOT be claimed by usbfs ?
I grepped the source code for usage of dev_set_uevent_suppress, but it seems not to be 100%
clear how that should be used (sometimes uevents are only suppressed temporarily to implement
a delay, sometimes they are actually kept suppressed).
I will prepare/send an alternative.
with best regards
Ingo
PS:
> ...
> No need for this in the changelog body :)
I should have read the documentation about how to send correct E-Mails for patches more intensively.
I just found out about "git send-email" and had not set it up (did now...). I am sorry.
> And did you send this patch twice?
Unfortunately yes: I was struggling how to format this correctly.
prev parent reply other threads:[~2019-10-10 12:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 9:21 [PATCH] USB: usbfs: Suppress emission of uevents for interfaces handled via usbfs Ingo Rohloff
2019-10-09 10:38 ` Ingo Rohloff
2019-10-10 10:24 ` Greg KH
2019-10-10 12:53 ` Ingo Rohloff [this message]
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