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From: Kumaraparameshwaran Rathnavel <krath at cloudsimple.com>
Subject: Re: [SPDK] BDEV Registration
Date: Fri, 21 Oct 2016 09:39:03 +0530
Message-ID: <3439EAD2-ACB6-431A-BB54-D3AAF171C3AF@cloudsimple.com>
In-Reply-To: c22353ee-7e25-ff66-d9b9-085528f3aa84@intel.com
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Thanks Daniel.

When will the bdev subsystem get initialised? Which part of the code handle=
s the bdev subsystem initialisation.

Thanking You,
Param
> On 21-Oct-2016, at 3:29 AM, Daniel Verkamp <daniel.verkamp(a)intel.com> w=
rote:
> =

> On 10/20/2016 01:11 PM, Kumaraparameshwaran Rathnavel wrote:
>> Hi All,
>> =

>> I have just started using SPDK. I am in need to implement a NVMe/F targe=
t implementation using SPDK. I need to use the Virtual Subsystem. I see tha=
t there is support for RAM disks and I am using it as reference to my Virtu=
al implementation .
>> =

>> There is a function called SPDK_BDEV_MODULE_REGISTER in the file lib/bde=
v/malloc/blockdev_malloc.c.
>> =

>> How is this function getting called? Who calls this function
>> =

>> Regards
>> Param
> =

> Hi Param,
> =

> You can find the interface for writing new bdev modules in the header
> lib/bdev/bdev_module.h - this is where SPDK_BDEV_MODULE_REGISTER() is def=
ined.  This macro creates a constructor function that adds your bdev module=
's function pointer table (defined using a spdk_bdev_module_if) to a global=
 list.
> =

> Later, when the bdev subsystem is initialized, each bdev module will have=
 its module_init function called, where it should create its bdevs and regi=
ster them using spdk_bdev_register().  Currently, all of the bdevs in SPDK =
use our configuration file library to read from a common conf file when det=
ermining which bdevs are created and what options to use (e.g. the malloc b=
dev uses the [Malloc] section of the configuration file).
> =

> When registering a bdev, you must provide another set of function pointer=
s in fn_table which perform operations on the individual bdevs, like creati=
ng a new I/O channel and submitting I/O requests on a channel.
> =

> To hook up your bdev module in the NVMe over Fabrics target, you will als=
o want to modify mk/spdk.modules.mk to add your new module to the BLOCKDEV_=
MODULES list.  This adds linker options to all of the applications in the S=
PDK tree that use bdev modules.
> =

> Please let us know if you have any further questions - the bdev module AP=
I is still somewhat in flux and not well documented.
> =

> Thanks,
> -- Daniel
> _______________________________________________
> SPDK mailing list
> SPDK(a)lists.01.org
> https://lists.01.org/mailman/listinfo/spdk


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