netdev - Re: [PATCH net-next v2] net: nfc: nci: Turn data timeout into a module parameter and increase the default

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Message-ID: <518333811aeda4dc42445efd6d9cee6cc580145a.camel@sarinay.com>
Date: Wed, 27 Aug 2025 19:48:33 +0200
From: Juraj Šarinay <juraj@...inay.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, mingo@...nel.org, horms@...nel.org, 
	tglx@...utronix.de
Subject: Re: [PATCH net-next v2] net: nfc: nci: Turn data timeout into a
 module parameter and increase the default

On Wed, 2025-08-27 at 15:29 +0200, Krzysztof Kozlowski wrote:

> CardOS is the software running on the NFC card, right? 

Yes it is. I may have been too specific, all I am saying is that I made
some measurements.

> If so, why would this be Linux kernel module param? Kernel runtime setup is really
> independent of what NFC card people will use.

I suggested a tunable timeout because I am not sure what the new
universal upper bound should be. It may depend on the NFC card one is
communicating with. I have since learned that module parameters are
strongly discouraged (within netdev at least).

> I think this should be unconditionally raised

I am fine with that, but would argue for an even more generous timeout.
Five seconds, say? One can always set a shorter SO_RCVTIMEO from user
space if needed.

Ideally, the kernel would also honor a longer SO_RCVTIMEO and treat
NCI_DATA_TIMEOUT as a default rather than a rigid limit, completely
obviating my subjective need for a parameter. I have not explored the
idea further, given that a somewhat higher value of NCI_DATA_TIMEOUT
solves most problems.

Best,
Juraj