From: Michal Pecio <michal.pecio@gmail.com>
To: Giuseppe Piscitelli <ooonea@gmail.com>
Cc: linux-usb@vger.kernel.org, stern@rowland.harvard.edu,
gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org
Subject: Re: [RFC PATCH v2] USB: core: emit a device-level modalias
Date: Wed, 7 Oct 2026 22:41:15 +0200 [thread overview]
Message-ID: <20261007224115.755ce40d.michal.pecio@gmail.com> (raw)
In-Reply-To: <20261007191130.8652-1-ooonea@gmail.com>
On Wed, 7 Oct 2026 21:11:30 +0200, Giuseppe Piscitelli wrote:
> On the first insertion of an iPhone (05ac:12a8) after boot, an already
> running usbmuxd can select USB configuration 4 before the charging driver
> apple-mfi-fastcharge loads. usbmuxd is a userspace daemon that uses libusb
> to communicate with Apple devices; apple-mfi-fastcharge is a USB device
> driver that enables their higher charging current.
>
> USB device uevents have no MODALIAS. The charging module instead loads
> from an interface uevent. Its registration reprobes the device, unbinds
> the generic driver and calls usb_set_configuration(udev, -1), tearing down
> the interfaces and interrupting usbmuxd's transfers.
What is actually the appeal of apple-mfi-fastcharge?
It seems to just issues some control requests to the device when
commanded by userspace. Userspace could do the same with libusb,
apparently without unbinding drivers, changing configurations or
even claiming USB interfaces. I just tried a simple program that
queries GET_CONFIGURATION, with no disruption to kernel drivers
or other libusb applications using the same device concurrently.
Then simply blacklist the kernel module and all its problems are
gone forever without one line of kernel code?
Regards,
Michal
prev parent reply other threads:[~2026-10-07 20:41 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-07 16:17 [RFC PATCH] " Giuseppe Piscitelli
2026-10-07 17:55 ` Alan Stern
2026-10-07 19:11 ` [RFC PATCH v2] " Giuseppe Piscitelli
2026-10-07 19:17 ` Alan Stern
2026-10-07 20:41 ` Michal Pecio [this message]
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