netdev - Re: [PATCH net-next v2] net: sysfs: Do not create sysfs for non BQL device

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Date: Fri, 16 Feb 2024 09:29:05 -0800
From: Stephen Hemminger <stephen@...workplumber.org>
To: Breno Leitao <leitao@...ian.org>
Cc: kuba@...nel.org, davem@...emloft.net, pabeni@...hat.com,
 edumazet@...gle.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 horms@...nel.org, Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH net-next v2] net: sysfs: Do not create sysfs for non BQL
 device

On Fri, 16 Feb 2024 01:41:52 -0800
Breno Leitao <leitao@...ian.org> wrote:

> +static bool netdev_uses_bql(const struct net_device *dev)
> +{
> +	if (dev->features & NETIF_F_LLTX ||
> +	    dev->priv_flags & IFF_NO_QUEUE)
> +		return false;
> +
> +	return IS_ENABLED(CONFIG_BQL);
> +}

Various compilers will warn about missing parens in that expression.
It is valid but mixing & and || can be bug trap.

	if ((dev->features & NETIF_F_LLTX) || (dev->priv_flags & IFF_NO_QUEUE))
		return false;

Not all drivers will be using bql, it requires driver to have that code.
So really it means driver could be using BQL.
Not sure if there is a way to find out if driver has the required BQL bits.