linux-kernel - Re: [PATCH] iwlwifi: Demote messages about fw flags size to info

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Date:   Mon, 24 Jul 2017 11:01:27 +0000
From:   "Coelho, Luciano" <luciano.coelho@...el.com>
To:     linuxwifi <linuxwifi@...el.com>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "jprvita@...il.com" <jprvita@...il.com>,
        "Berg, Johannes" <johannes.berg@...el.com>,
        "Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>
CC:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "linux@...lessm.com" <linux@...lessm.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jprvita@...lessm.com" <jprvita@...lessm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iwlwifi: Demote messages about fw flags size to info

On Fri, 2017-07-21 at 07:51 -0700, João Paulo Rechi Vita wrote:
> These messages are not reporting a real error, just the fact that the
> firmware knows about more flags then the driver.
> 
> Currently these messages are presented to the user during boot if there
> is no bootsplash covering the console, sometimes even if the boot splash
> is enabled but has not started yet by the time this message is shown.
> 
> Demoting it to the info level helps having a clean boot process.
> 
> Signed-off-by: João Paulo Rechi Vita <jprvita@...lessm.com>
> ---

The idea with this error is that if the firmware is too new and includes
a TLV that we are not aware of, there can be unexpected issues.  For
instance, sometimes the FW API changes some of its structures and we use
TLVs to know which one to use.  If a new struct is in use by the
firmware but not by the driver, problems will occur.

Recently we accidentally omitted one TLV from the driver and released a
new firmware that had it set... That's the error you are currently
seeing.  We have a bugzilla entry[1] and it is fixed in our internal
tree.  The fix will be sent upstream in the next -fixes round we send
out.

This specific case is harmless, but I'd rather keep this message as an
error, because in other situations it could lead to unexpected
behavioir, so I prefer to keep it very visible.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=196195

--
Cheers,
Luca.