Re: [PATCH 04/10] ata: add ata_is_fpdma() accessor

From: Tejun Heo <tj@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: hare@suse.com, damien.lemoal@hgst.com, linux-ide@vger.kernel.org,
	Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH 04/10] ata: add ata_is_fpdma() accessor
Date: Thu, 14 Jul 2016 10:37:56 -0400	[thread overview]
Message-ID: <20160714143756.GF15005@htj.duckdns.org> (raw)
In-Reply-To: <1468454751-12466-5-git-send-email-hch@lst.de>

Hello,

I'm still a bit confused about this patch.

On Thu, Jul 14, 2016 at 09:05:45AM +0900, Christoph Hellwig wrote:
> diff --git a/drivers/ata/sata_fsl.c b/drivers/ata/sata_fsl.c
> index a723ae9..acfb865 100644
> --- a/drivers/ata/sata_fsl.c
> +++ b/drivers/ata/sata_fsl.c
> @@ -534,7 +534,7 @@ static void sata_fsl_qc_prep(struct ata_queued_cmd *qc)
>  	VPRINTK("Dumping cfis : 0x%x, 0x%x, 0x%x\n",
>  		cd->cfis[0], cd->cfis[1], cd->cfis[2]);
>  
> -	if (qc->tf.protocol == ATA_PROT_NCQ) {
> +	if (ata_is_fpdma(qc->tf.protocol)) {

ata_is_fpdma() tests NCQ or DMA.  Is this right?

> --- a/drivers/ata/sata_mv.c
> +++ b/drivers/ata/sata_mv.c
> @@ -1173,7 +1173,7 @@ static void mv_set_irq_coalescing(struct ata_host *host,
>  static void mv_start_edma(struct ata_port *ap, void __iomem *port_mmio,
>  			 struct mv_port_priv *pp, u8 protocol)
>  {
> -	int want_ncq = (protocol == ATA_PROT_NCQ);
> +	int want_ncq = (ata_is_fpdma(protocol));

Let's get rid of the parentheses while at it.

>  
>  	if (pp->pp_flags & MV_PP_FLAG_EDMA_EN) {
>  		int using_ncq = ((pp->pp_flags & MV_PP_FLAG_NCQ_EN) != 0);
> @@ -2156,8 +2156,7 @@ static void mv_qc_prep_iie(struct ata_queued_cmd *qc)
>  	unsigned in_index;
>  	u32 flags = 0;
>  
> -	if ((tf->protocol != ATA_PROT_DMA) &&
> -	    (tf->protocol != ATA_PROT_NCQ))
> +	if (!ata_is_fpdma(tf->protocol))

This is actually testing !DMA && !NCQ and an equivalent conversion but
the rest aren't.

> diff --git a/drivers/ata/sata_nv.c b/drivers/ata/sata_nv.c
> index 734f563..89e36aa 100644
> --- a/drivers/ata/sata_nv.c
> +++ b/drivers/ata/sata_nv.c
> @@ -1407,7 +1407,7 @@ static void nv_adma_qc_prep(struct ata_queued_cmd *qc)
>  	cpb->next_cpb_idx	= 0;
>  
>  	/* turn on NCQ flags for NCQ commands */
> -	if (qc->tf.protocol == ATA_PROT_NCQ)
> +	if (ata_is_fpdma(qc->tf.protocol))
>  		ctl_flags |= NV_CPB_CTL_QUEUE | NV_CPB_CTL_FPDMA;

And I don't know why testing NCQ or DMA would be safe for places like
this.

> +	ATA_PROT_FLAG_FPDMA	= ATA_PROT_FLAG_NCQ | ATA_PROT_FLAG_DMA,
...
> +static inline bool ata_is_fpdma(u8 prot)
> +{
> +	return ata_prot_flags(prot) & ATA_PROT_FLAG_FPDMA;
> +}

???

Thanks.

-- 
tejun