Re: [PATCH 6/9] snic:Add low level queuing interfaces

[Hannes Reinecke <hare@suse.de>]

On 02/10/2015 05:43 PM, Narsimhulu Musini wrote:
> These files contain low level queueing interfaces includes
> hardware queues, and management of hardware features.
> 
> Signed-off-by: Narsimhulu Musini <nmusini@cisco.com>
> Signed-off-by: Sesidhar Baddela <sebaddel@cisco.com>
> ---
>  drivers/scsi/snic/cq_desc.h       |  77 ++++
>  drivers/scsi/snic/cq_enet_desc.h  |  38 ++
>  drivers/scsi/snic/vnic_cq.c       |  86 ++++
>  drivers/scsi/snic/vnic_cq.h       | 120 +++++
>  drivers/scsi/snic/vnic_cq_fw.h    |  62 +++
>  drivers/scsi/snic/vnic_dev.c      | 895 ++++++++++++++++++++++++++++++++++++++
>  drivers/scsi/snic/vnic_dev.h      | 165 +++++++
>  drivers/scsi/snic/vnic_devcmd.h   | 393 +++++++++++++++++
>  drivers/scsi/snic/vnic_intr.c     |  59 +++
>  drivers/scsi/snic/vnic_intr.h     | 127 ++++++
>  drivers/scsi/snic/vnic_resource.h |  68 +++
>  drivers/scsi/snic/vnic_snic.h     |  54 +++
>  drivers/scsi/snic/vnic_stats.h    |  68 +++
>  drivers/scsi/snic/vnic_wq.c       | 236 ++++++++++
>  drivers/scsi/snic/vnic_wq.h       | 187 ++++++++
>  drivers/scsi/snic/wq_enet_desc.h  |  96 ++++
>  16 files changed, 2731 insertions(+)
>  create mode 100644 drivers/scsi/snic/cq_desc.h
>  create mode 100644 drivers/scsi/snic/cq_enet_desc.h
>  create mode 100644 drivers/scsi/snic/vnic_cq.c
>  create mode 100644 drivers/scsi/snic/vnic_cq.h
>  create mode 100644 drivers/scsi/snic/vnic_cq_fw.h
>  create mode 100644 drivers/scsi/snic/vnic_dev.c
>  create mode 100644 drivers/scsi/snic/vnic_dev.h
>  create mode 100644 drivers/scsi/snic/vnic_devcmd.h
>  create mode 100644 drivers/scsi/snic/vnic_intr.c
>  create mode 100644 drivers/scsi/snic/vnic_intr.h
>  create mode 100644 drivers/scsi/snic/vnic_resource.h
>  create mode 100644 drivers/scsi/snic/vnic_snic.h
>  create mode 100644 drivers/scsi/snic/vnic_stats.h
>  create mode 100644 drivers/scsi/snic/vnic_wq.c
>  create mode 100644 drivers/scsi/snic/vnic_wq.h
>  create mode 100644 drivers/scsi/snic/wq_enet_desc.h
> 
> diff --git a/drivers/scsi/snic/cq_desc.h b/drivers/scsi/snic/cq_desc.h
> new file mode 100644
> index 0000000..a529056
> --- /dev/null
> +++ b/drivers/scsi/snic/cq_desc.h
> @@ -0,0 +1,77 @@
> +/*
> + * Copyright 2014 Cisco Systems, Inc.  All rights reserved.
> + *
> + * This program is free software; you may redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
> + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
> + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
> + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
> + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
> + * SOFTWARE.
> + */
> +
> +#ifndef _CQ_DESC_H_
> +#define _CQ_DESC_H_
> +
> +/*
> + * Completion queue descriptor types
> + */
> +enum cq_desc_types {
> +	CQ_DESC_TYPE_WQ_ENET = 0,
> +	CQ_DESC_TYPE_DESC_COPY = 1,
> +	CQ_DESC_TYPE_WQ_EXCH = 2,
> +	CQ_DESC_TYPE_RQ_ENET = 3,
> +	CQ_DESC_TYPE_RQ_FCP = 4,
> +};
> +
> +/* Completion queue descriptor: 16B
> + *
> + * All completion queues have this basic layout.  The
> + * type_specific area is unique for each completion
> + * queue type.
> + */
> +struct cq_desc {
> +	__le16 completed_index;
> +	__le16 q_number;
> +	u8 type_specific[11];
> +	u8 type_color;
> +};
> +
> +#define CQ_DESC_TYPE_BITS        4
> +#define CQ_DESC_TYPE_MASK        ((1 << CQ_DESC_TYPE_BITS) - 1)
> +#define CQ_DESC_COLOR_MASK       1
> +#define CQ_DESC_COLOR_SHIFT      7
> +#define CQ_DESC_Q_NUM_BITS       10
> +#define CQ_DESC_Q_NUM_MASK       ((1 << CQ_DESC_Q_NUM_BITS) - 1)
> +#define CQ_DESC_COMP_NDX_BITS    12
> +#define CQ_DESC_COMP_NDX_MASK    ((1 << CQ_DESC_COMP_NDX_BITS) - 1)
> +
> +static inline void cq_desc_dec(const struct cq_desc *desc_arg,
> +	u8 *type, u8 *color, u16 *q_number, u16 *completed_index)
> +{
> +	const struct cq_desc *desc = desc_arg;
> +	const u8 type_color = desc->type_color;
> +
> +	*color = (type_color >> CQ_DESC_COLOR_SHIFT) & CQ_DESC_COLOR_MASK;
> +
> +	/*
> +	 * Make sure color bit is read from desc *before* other fields
> +	 * are read from desc.  Hardware guarantees color bit is last
> +	 * bit (byte) written.  Adding the rmb() prevents the compiler
> +	 * and/or CPU from reordering the reads which would potentially
> +	 * result in reading stale values.
> +	 */
> +	rmb();
> +
> +	*type = type_color & CQ_DESC_TYPE_MASK;
> +	*q_number = le16_to_cpu(desc->q_number) & CQ_DESC_Q_NUM_MASK;
> +	*completed_index = le16_to_cpu(desc->completed_index) &
> +		CQ_DESC_COMP_NDX_MASK;
> +}
Now you're getting inconsistent.

Either you care for endianness, in which case you need to protect
_all_ hardware-dependent structure with cpu_to_XX and friends,
or you claim that you're hardware is unique to a given
architecture/machine, in which case you can skip the byte swapping.

But mixing them is not a good idea.

(And that comment is valid for the entire patch).

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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