linux-kernel - Re: [RESEND PATCH v3] net: usb: usbnet: update __usbnet_{read|write}

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Message-ID: <20201104162444.66b5cc56@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 4 Nov 2020 16:24:44 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Anant Thazhemadam <anant.thazhemadam@...il.com>
Cc:     Oliver Neukum <oneukum@...e.com>,
        "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [RESEND PATCH v3] net: usb: usbnet: update
 __usbnet_{read|write}_cmd() to use new API

On Mon,  2 Nov 2020 23:09:46 +0530 Anant Thazhemadam wrote:
> Currently, __usbnet_{read|write}_cmd() use usb_control_msg().
> However, this could lead to potential partial reads/writes being
> considered valid, and since most of the callers of
> usbnet_{read|write}_cmd() don't take partial reads/writes into account
> (only checking for negative error number is done), and this can lead to
> issues.
> 
> However, the new usb_control_msg_{send|recv}() APIs don't allow partial
> reads and writes.
> Using the new APIs also relaxes the return value checking that must
> be done after usbnet_{read|write}_cmd() is called.
> 
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@...il.com>

So you're changing the semantics without updating the callers?

I'm confused. 

Is this supposed to be applied to some tree which already has the
callers fixed?

At a quick scan at least drivers/net/usb/plusb.c* would get confused 
as it compares the return value to zero and 0 used to mean "nothing
transferred", now it means "all good", no? 

* I haven't looked at all the other callers