[parted-devel] [PATCH 1/2] fdasd: geometry handling updated from upstream s390-tools

[Viktor Mihajlovski]

On 22.09.2015 08:49, Phil Susi wrote:
> On 9/15/2015 9:02 AM, Hendrik Brueckner wrote:
>> Use bzero for initialization to make sure all struct members are
>> properly cleared. Also changed partition list handling code to be
>> more similar to upstream s390-tools fdasd.
>
>  From the bzero(3):
>
> CONFORMING TO
>         4.3BSD.  This function is deprecated (marked as LEGACY in
> POSIX.1-2001): use memset(3) in new  pro‐
>         grams.  POSIX.1-2008 removes the specification of bzero().
>
I prefer to use memset but wanted to stay in style (bzero is used
all over the place in the existing code).
>
> Also, could someone clue me in ( possibly point me to some docs ) about
> what this DASD stuff is and why it needs special ioctls to partition?
>
DASD is a s390-specific disk architecture. The technical term which
would be more accurate here is ECKD (enhanced count key data). In a
nutshell, the Linux block layer is not prepared to handle variable
block sizes of ECKD DASDs.
ECKD DASDs have to be formatted using a device specific ioctl. The
formatting will provide the more or less familiar block structure
(all blocks having the same size, typically 4K).
However, the first track of a DASD has to be in a specific format
called VTOC (volume table of contents) containing disk metadata.
Traditionally, there is an ioctl to interface with this data, which
however only works for a natively attached DASD.
This patch is removing the necessity for the ioctls if the transport
isn't native.

-- 

Mit freundlichen Grüßen/Kind Regards
    Viktor Mihajlovski

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