linux-kernel - Re: [PATCH 2/6] ibmvscsi: Add and use enums for valid CRQ header values

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Message-ID: <56B3ACC9.60009@linux.vnet.ibm.com>
Date:	Thu, 4 Feb 2016 13:55:53 -0600
From:	Manoj Kumar <manoj@...ux.vnet.ibm.com>
To:	Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>, JBottomley@...n.com
Cc:	martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	nfont@...ux.vnet.ibm.com, brking@...ux.vnet.ibm.com, hare@...e.de
Subject: Re: [PATCH 2/6] ibmvscsi: Add and use enums for valid CRQ header
 values

On 2/3/2016 5:28 PM, Tyrel Datwyler wrote:
> The PAPR defines four valid header values for the first byte of a
> CRQ message. Namely, an unused/empty message (0x00), a valid
> command/response entry (0x80), a valid initialization entry (0xC0),
> and a transport event (0xFF). Define these values as enums and use
> them in the code in place of their magic number equivalents.
>
> Signed-off-by: Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>
> ---
>   drivers/scsi/ibmvscsi/ibmvscsi.c | 14 +++++++-------
>   drivers/scsi/ibmvscsi/viosrp.h   |  7 +++++++
>   2 files changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
> index adfef9d..176260d 100644
> --- a/drivers/scsi/ibmvscsi/ibmvscsi.c
> +++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
> @@ -182,7 +182,7 @@ static struct viosrp_crq *crq_queue_next_crq(struct crq_queue *queue)
>
>   	spin_lock_irqsave(&queue->lock, flags);
>   	crq = &queue->msgs[queue->cur];
> -	if (crq->valid & 0x80) {
> +	if (crq->valid & VIOSRP_CRQ_VALID) {

After the switch to enums, bitwise operators are a bit misleading.
Especially in this case since multiple values would satisfy this
condition: VIOSRP_CRQ_VALID, VIOSRP_CRQ_INIT and
VIOSRP_CRQ_TRANSPORT.

If 'valid' will only have one of these four enums defined, would
this be better written as:

	if (crq->valid != VIOSRP_CRQ_FREE)

>   		if (++queue->cur == queue->size)
>   			queue->cur = 0;
>
> @@ -231,7 +231,7 @@ static void ibmvscsi_task(void *data)
>   		/* Pull all the valid messages off the CRQ */
>   		while ((crq = crq_queue_next_crq(&hostdata->queue)) != NULL) {
>   			ibmvscsi_handle_crq(crq, hostdata);
> -			crq->valid = 0x00;
> +			crq->valid = VIOSRP_CRQ_FREE;
>   		}
>
>   		vio_enable_interrupts(vdev);
> @@ -239,7 +239,7 @@ static void ibmvscsi_task(void *data)
>   		if (crq != NULL) {
>   			vio_disable_interrupts(vdev);
>   			ibmvscsi_handle_crq(crq, hostdata);
> -			crq->valid = 0x00;
> +			crq->valid = VIOSRP_CRQ_FREE;
>   		} else {
>   			done = 1;
>   		}
> @@ -474,7 +474,7 @@ static int initialize_event_pool(struct event_pool *pool,
>   		struct srp_event_struct *evt = &pool->events[i];
>   		memset(&evt->crq, 0x00, sizeof(evt->crq));
>   		atomic_set(&evt->free, 1);
> -		evt->crq.valid = 0x80;
> +		evt->crq.valid = VIOSRP_CRQ_VALID;
>   		evt->crq.IU_length = cpu_to_be16(sizeof(*evt->xfer_iu));
>   		evt->crq.IU_data_ptr = cpu_to_be64(pool->iu_token +
>   			sizeof(*evt->xfer_iu) * i);
> @@ -1767,7 +1767,7 @@ static void ibmvscsi_handle_crq(struct viosrp_crq *crq,
>   	struct srp_event_struct *evt_struct =
>   			(__force struct srp_event_struct *)crq->IU_data_ptr;
>   	switch (crq->valid) {
> -	case 0xC0:		/* initialization */
> +	case VIOSRP_CRQ_INIT:		/* initialization */
>   		switch (crq->format) {
>   		case 0x01:	/* Initialization message */
>   			dev_info(hostdata->dev, "partner initialized\n");
> @@ -1791,7 +1791,7 @@ static void ibmvscsi_handle_crq(struct viosrp_crq *crq,
>   			dev_err(hostdata->dev, "unknown crq message type: %d\n", crq->format);
>   		}
>   		return;
> -	case 0xFF:	/* Hypervisor telling us the connection is closed */
> +	case VIOSRP_CRQ_TRANSPORT:	/* Hypervisor telling us the connection is closed */
>   		scsi_block_requests(hostdata->host);
>   		atomic_set(&hostdata->request_limit, 0);
>   		if (crq->format == 0x06) {
> @@ -1807,7 +1807,7 @@ static void ibmvscsi_handle_crq(struct viosrp_crq *crq,
>   			ibmvscsi_reset_host(hostdata);
>   		}
>   		return;
> -	case 0x80:		/* real payload */
> +	case VIOSRP_CRQ_VALID:		/* real payload */
>   		break;
>   	default:
>   		dev_err(hostdata->dev, "got an invalid message type 0x%02x\n",
> diff --git a/drivers/scsi/ibmvscsi/viosrp.h b/drivers/scsi/ibmvscsi/viosrp.h
> index d1044e9..17f2de0 100644
> --- a/drivers/scsi/ibmvscsi/viosrp.h
> +++ b/drivers/scsi/ibmvscsi/viosrp.h
> @@ -51,6 +51,13 @@ union srp_iu {
>   	u8 reserved[SRP_MAX_IU_LEN];
>   };
>
> +enum viosrp_crq_headers {
> +	VIOSRP_CRQ_FREE = 0x00,
> +	VIOSRP_CRQ_VALID = 0x80,
> +	VIOSRP_CRQ_INIT = 0xC0,
> +	VIOSRP_CRQ_TRANSPORT = 0xFF
> +};
> +
>   enum viosrp_crq_formats {
>   	VIOSRP_SRP_FORMAT = 0x01,
>   	VIOSRP_MAD_FORMAT = 0x02,
>