linux-kernel - Re: [PATCH] enic: add ethtool get

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Message-ID: <0201165C-1677-4525-A38B-4DB1E6F6AB68@nutanix.com>
Date: Thu, 20 Jun 2024 19:49:45 +0000
From: Jon Kohler <jon@...anix.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Przemek Kitszel <przemyslaw.kitszel@...el.com>,
        Christian Benvenuti
	<benve@...co.com>,
        Satish Kharat <satishkh@...co.com>,
        "David S. Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
	<pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Larysa Zaremba
	<larysa.zaremba@...el.com>
Subject: Re: [PATCH] enic: add ethtool get_channel support



> On Jun 19, 2024, at 8:04 PM, Jakub Kicinski <kuba@...nel.org> wrote:
> 
> On Tue, 18 Jun 2024 16:39:40 +0000 Jon Kohler wrote:
>> Looking through how other drivers do this, I didn’t get a sense that
>> any other drivers were stacking rx_count + combined_count together.
>> 
>> Also, enic and the underlying Cisco VIC hardware appears to be 
>> fairly specific that the queues they provision at the hardware level are
>> either RX or TX and not a unified ring or something to that effect.
>> 
>> I took that to mean that we would never call anything ‘combined’ in
>> the context of this driver.
> 
> channel is a bit of an old term, think about interrupts more than
> queues. ethtool man page has the most informative description.

Thanks for the pointer on man ethtool - one question, Przemek had
brought up a good point that ethtool uapi says that combined queues
valid values start at 1; however, I don’t see anything that enforces that
point in the code or the man page.

Should I just omit that completely from the change, since the fields
are zero initialized anyhow?

> 
> Looking at this driver, specifically enic_dev_init() I'd venture
> something along the lines of:
> 
> switch (vnic_dev_get_intr_mode(enic->vdev)) { 
> default:
> channels->combined = 1;
> break;                
> case VNIC_DEV_INTR_MODE_MSIX: 
> channels->rx_count = enic->rq_count;
> channels->tx_count = enic->wq_count;
> break;
>        }
> 
> Please not that you don't have to zero out unused fields, they come
> zero-initilized.

Ok thanks, I’ll see what I can cook up in a V2 patch. 

> -- 
> pw-bot: cr