RE: [EXTERNAL] Re: issues with cdc ncm host class driver

["Purohit, Kaushal" <kaushal.purohit@ti.com>]

Oliver, Thanks for the quick confirmation. Tracked in kernel Bugzilla by "Bug 217290".

-----Original Message-----
From: Oliver Neukum <oneukum@suse.com> 
Sent: Monday, April 3, 2023 3:39 PM
To: Purohit, Kaushal <kaushal.purohit@ti.com>; stable@vger.kernel.org
Cc: regressions@lists.linux.dev; linux-usb@vger.kernel.org
Subject: [EXTERNAL] Re: issues with cdc ncm host class driver

On 03.04.23 08:14, Purohit, Kaushal wrote:
> Hi,
> 

Hi,

> Referring to patch with commit ID (*e10dcb1b6ba714243ad5a35a11b91cc14103a9a9*).
> 
> This is a spec violation for CDC NCM class driver. Driver clearly says 
> the significance of network capabilities. (snapshot below)
> 
> However, with the mentioned patch these values are disrespected and commands specific to these capabilities are sent from the host regardless of device' capabilities to handle them.

Right. So for your device, the correct behavior would be to do nothing, wouldn't it? The packets would be delivered and the host needs to filter and discard unrequested packets.

> Currently we are setting these bits to 0 indicating no capabilities on our device and still we observe that Host (Linux kernel host cdc driver) has been sending requests specific to these capabilities.
> 
> Please let me know if there is a better way to indicate host that device does not have these capabilities.

no you are doing things as they are supposed to be done and the host is at fault. This kernel bug needs to be fixed.

	Regards
		Oliver