linux-kernel - Re: [PATCH 1/3] nvme: Add Arbitration Burst support

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Message-ID: <20200624025715.GB1291930@dhcp-10-100-145-180.wdl.wdc.com>
Date:   Tue, 23 Jun 2020 19:57:15 -0700
From:   Keith Busch <kbusch@...nel.org>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     axboe@...com, hch@....de, sagi@...mberg.me, baolin.wang7@...il.com,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] nvme: Add Arbitration Burst support

On Tue, Jun 23, 2020 at 09:24:32PM +0800, Baolin Wang wrote:
> +void nvme_set_arbitration_burst(struct nvme_ctrl *ctrl)
> +{
> +	u32 result;
> +	int status;
> +
> +	if (!ctrl->rab)
> +		return;
> +
> +	/*
> +	 * The Arbitration Burst setting indicates the maximum number of
> +	 * commands that the controller may launch at one time from a
> +	 * particular Submission Queue. It is recommended that host software
> +	 * configure the Arbitration Burst setting as close to the recommended
> +	 * value by the controller as possible.
> +	 */
> +	status = nvme_set_features(ctrl, NVME_FEAT_ARBITRATION, ctrl->rab,

Since 'rab' is an 8-bit field, but the feature's AB value is only 3
bits, we should add a validity check.

> +}
> +EXPORT_SYMBOL_GPL(nvme_set_arbitration_burst);

I don't see any particular reason to export this function just for the
pci transport to use. Just make it a local static function an call it
from nvme_init_identify().