netdev - RE: [PATCH net-next 0/3] r8152: configuration setting

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Message-ID: <0835B3720019904CB8F7AA43166CEEB201026170@RTITMBSV03.realtek.com.tw>
Date:   Thu, 8 Sep 2016 13:02:01 +0000
From:   Hayes Wang <hayeswang@...ltek.com>
To:     Bjørn Mork <bjorn@...k.no>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        nic_swsd <nic_swsd@...ltek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Oliver Neukum <oliver@...kum.org>
Subject: RE: [PATCH net-next 0/3] r8152: configuration setting

Bjørn Mork [mailto:bjorn@...k.no]
> Sent: Thursday, September 08, 2016 3:55 PM
[...]
> Yes, I see that.  But is that strictly necessary? Couldn't you just say:
> "CDC ECM is supported by cdc_ether and therefore limited to the features
> implemented by cdc_ether.  If you want feature X, then please use our
> vendor specific mode with the r8152 driver?"

My customs have a case that they must force the speed to 100M
for some reasons. I also wish to implement the driver as simple
as possible, but I don't think I could determine this. I accept
you reject my patches. However, I couldn't deny the requests
from the boss or customs without doing anything. I must prove
the way is unacceptable.

[...]
> Each USB configuation comes with a set of descriptors identifying the
> functions, and USB interface drivers attach to the functions they
> support.  The user can dynamically switch the device from e.g. cfg #1 to
> cfg #3 by writing "3" to /sys/bus/usb/devices/<port>/bConfigurationValue
> This will cause the ECM and ACM USB interfaces to disappear, and the
> associated class drivers will unbind, and new vendor specific USB
> interfaces appear instead, causing a matching vendor specific driver to
> load and bind.
> 
> Naturally, end users will not switch configurations all the time.  They
> will select the configuration providing the set of functions they want.
> If this is different from the default configuration  selected by the
> Linux USB core, then that's a simple udev rule to update the
> bConfigurationValue sysfs attribute on device disceovery.

I tested above method before. And I found that the cdc_ether
was loaded before switching the configuration. The behavior
of loading one driver and changing to another driver has
opportunity to let our some previous chips become abnormal.
To switch configuration is fine. However, it may have problem
to switch driver. That is why the current kernel only supports
vendor mode. If the method works fine, I have no trouble now.

Best Regards,
Hayes