RE: [PATCH] drivers/scsi/emcctd: drivers/scsi/emcctd: Client driver implementation for EMC-Symmetrix GuestOS emulated Cut-Through Device

Hello Greg,

Thanks for taking out time to review the patch. Please find my replies inlined...
Will post the next patch for modifications soon.

-----Original Message-----
From: Greg KH [mailto:greg@kroah.com]
Sent: Tuesday, January 19, 2016 11:42 PM
To: Singhal, Maneesh
Cc: linux-scsi@vger.kernel.org; linux-kernel@vger.kernel.org;
JBottomley@odin.com; martin.petersen@oracle.com; linux-
api@vger.kernel.org
Subject: Re: [PATCH] drivers/scsi/emcctd: drivers/scsi/emcctd: Client
driver implementation for EMC-Symmetrix GuestOS emulated Cut-
Through Device

On Tue, Jan 19, 2016 at 11:58:06AM +0000, Singhal, Maneesh wrote:

quoted

Hello,
Kindly review the following patch for the following driver to be

added

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in SCSI subsystem -

Regards
Maneesh

----------------------------------------------------------------------
------

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From f3c4b836d6f130b1d7ded618002c8164f8f4a06d Mon Sep 17

00:00:00

quoted

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2001

From: "maneesh.singhal" <redacted>
Date: Tue, 19 Jan 2016 06:39:35 -0500
Subject: [PATCH] [PATCH] drivers/scsi/emcctd: Client driver
implementation for  EMC-Symmetrix GuestOS emulated Cut-

Through Device.

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The patch is a driver implementation  EMC-Symmetrix GuestOS

emulated

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Cut-Through Device. The Cut-Through Device PCI emulation is
implemented for GuestOS environments in the HyperMax OS.

GuestOS

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environments allows loading of any x86 compliant operating systems

like Linux/FreeBSD etc.

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The client driver is a SCSI HBA implementation which interfaces with
SCSI midlayer in the north-bound interfaces and connects with the
emulated PCI device on the south side.

The PCI vendor ID:product ID for emulated Cut-Through Device is

0x1120:0x1B00.

quoted

Signed-off-by: maneesh.singhal <redacted>
---
 Documentation/scsi/emcctd.txt           |   57 +
 MAINTAINERS                             |    9 +
 drivers/scsi/Kconfig                    |    1 +
 drivers/scsi/Makefile                   |    1 +
 drivers/scsi/emcctd/Kconfig             |    7 +
 drivers/scsi/emcctd/Makefile            |    1 +
 drivers/scsi/emcctd/README              |   10 +
 drivers/scsi/emcctd/emc_ctd_interface.h |  386 +++++
 drivers/scsi/emcctd/emcctd.c            | 2840

+++++++++++++++++++++++++++++++

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 drivers/scsi/emcctd/emcctd.h            |  232 +++
 10 files changed, 3544 insertions(+)
 create mode 100644 Documentation/scsi/emcctd.txt  create mode

100644

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drivers/scsi/emcctd/Kconfig  create mode 100644
drivers/scsi/emcctd/Makefile  create mode 100644
drivers/scsi/emcctd/README  create mode 100644
drivers/scsi/emcctd/emc_ctd_interface.h
 create mode 100644 drivers/scsi/emcctd/emcctd.c  create mode

100644

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drivers/scsi/emcctd/emcctd.h

diff --git a/Documentation/scsi/emcctd.txt

b/Documentation/scsi/emcctd.txt new file mode 100644 index
0000000..bcafc87

--- /dev/null
+++ b/Documentation/scsi/emcctd.txt

@@ -0,0 +1,56 @@
+This file contains brief information about the EMC Cut-Through

Driver (emcctd).

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+The driver is currently maintained by Singhal, Maneesh
+(maneesh.singhal@emc.com)
+
+Last modified: Mon Jan 18 2016 by Maneesh Singhal
+
+BASICS
+
+Its a client driver implementation for EMC-Symmetrix GuestOS

emulated

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+Cut-Through Device. The Cut-Through Device PCI emulation is
+implemented for GuestOS environments in the HyperMax OS.

GuestOS

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+environments allows loading of any x86 compliant operating

systems like Linux/FreeBSD etc.

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+
+The client driver is a SCSI HBA implementation which interfaces with
+SCSI midlayer in the north-bound interfaces and connects with the
+emulated PCI device on the south side.
+
+The PCI vendor ID:product ID for emulated Cut-Through Device is

0x1120:0x1B00.

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+
+VERSIONING
+
+The Version of the driver is maintained as 2.0.0.X, where 2 refers to
+the CTD protocol in use, and X refers to the ongoing version of the

driver.

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+
+
+SYSFS SUPPORT
+
+The driver creates the directory /sys/module/emcctd and

populates it

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+with version file and a directory for various parameters as described
+in MODULE PARAMETERS section.
+
+PROCFS SUPPORT
+
+The driver creates the directory /proc/emc and creates files
+emcctd_stats_x where 'x' refers to the PCI emulation number this

client driver connected to.

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+These files cotains WWN information and IO statistics for the
+particular PCI emulation.

No, no driver should be adding proc files, please use sysfs or debugfs
for debugging things.

[MS>] Sure.

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+MODULE PARAMETERS

No driver should be using module parameters anymore, again, please
use the correct interfaces.

[MS>] Yes got that

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+
+The supported parameters which could add debuggability or change

the

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+runtime behavior of the driver are as following:
+
+ctd_debug=0 | 1		Enable driver debug messages(0=off,

1=on)

Use the dynamic debugging interface, don't make a custom one just
for your tiny, single, driver.

[MS>] Sure. Will fix this.

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+
+max_luns=xx		Specify the maximum number of LUN's

per

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+			host(default=16384)

Why can't this be dynamic?  Why do you need a static number?

[MS>] Will fix this

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+
+cmd_per_lun=xx		Specify the maximum commands per

lun(default=16)

Why do you need to change this?  Why can't it be dynamic?

[MS>] Yes it can be. Will fix

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+
+DEBUGGING HINTS
+
+Debugging code is now compiled in by default but debugging is

turned

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+off with the kernel module parameter debug_flag defaulting to 0.

Again, no, use the dynamic debug interface, don't make something
"special" just for a single driver, we spent a lot of time trying to unify
everything, don't go backwards.

[MS>] Sure. Thanks

thanks,

greg k-h