hdx to sdx change in 2.6.28

Nathan Coulson conathan at gmail.com
Sun Jan 25 12:42:33 PST 2009


On Sat, Jan 24, 2009 at 5:23 PM, alupu <alupu02 at gmail.com> wrote:
> Hi Simon,
>
> On Sat, Jan 24, 2009 at 6:07 AM, Simon Geard wrote:
>> On Wed, 2009-01-14 at 21:15 -0500, alupu wrote:
>>> - QUESTION
>>> Does anybody know anything about the transition to 2.6.28 changing the
>>> "view" of the system to a "Universal", "Uniform", "Consistent", "SATA
>>> centric", etc.?
>
>> Disclaimer - I'm speaking only as someone who uses this stuff, not as
>> any kind of kernel expert.
>
> I don't know about that, but your comments are _very_ informative.
> Many thanks.
>
>> Shortly after SATA drives started coming out, the kernel developers
>> started work on a new framework for hard-drive access, called libATA -
>> it's not SATA centric as such, but it was created to make supporting
>> SATA easier, and to remedy deficiencies in the old system. Because of
>> that, almost all SATA drivers use this framework, but they've also been
>> working on replacing old PATA drivers with new ones for the new
>> framework.
>>
>> As with the usb-storage framework for dealing with flash drives and
>> stuff, this new framework uses a lot of infrastructure that came
>> originally from SCSI, hence the change in device names to sdX.
>>
>> As to why things have suddenly broken for you, I'm only guessing, but
>> I'd say 2.6.28 must have removed the old driver you were using - maybe
>> the Changelog has some mention of it?
>
> 1. First a correction with accompanying apology:
> Alex originally wrote:
> "System works as expected (i.e., just fine) on 2.6.27
> (actually up to 2.6.27.4;  haven't tested .5 - .10;  assume similar)"
> As mentioned, I jumped directly to 2.6.28 from 2.6.27.4.  Silly me.
> As fate would have it, in retrospect, things would have "broken" for me
> in the very next release, 2.6.27.5!
> Maybe this is why (B)LFS people (who are as of this writing at 2.6.27.8)
> ignored my thread "hdx to sdx change in 2.6.28" for all this time as
> just one of them "suspicious header" messages. :)
> And, BTW, there's even a 2.6.27.12!
> Another BTW:
> >From .5 to .12 the entry "SiS PATA support" is labeled "(experimental)".
> Starting with 2.6.28 (we're at 2.6.28.1), it's just that.
>
> 2. As for the ChangeLog, there's no mention of the "change" in 2.6.27.5.
> Luckily, 2.6.27.5 has only 59 commits.  Imagine what I went through
> with 2.6.28 which contains 9784!
> Granted, it's possible there was some talk about the new "framework"
> in pre-2.6.27.5, since in 2.6.27.4 there were already several
> "... PATA support" entries such as "VIA PATA support".
> For the record, I searched on "SiS", "support", "experimental", etc.
>
> 3. "[they] must have removed the old driver you were using ..."
> Unfortunately, I'm not at the subject PATA machine now, but I'm 99.9%
> sure that selecting the fateful "SiS PATA support" was an absolute must
> before all the machinations with GRUB and fstab fields in order to
> penetrate the "Kernel panic" wall.
> However. that leaves a nagging .1% grain of salt, meaning if I had
> futzed a little bit more with just GRUB and fstab, I'd've managed
> to fix things without needing "SiS PATA support" enabled.
> That is, to know conclusively whether the reason for the break was
> their pulling "the old driver" right from under me, or something else.
>
> 4. Sure, everybody would die to know exactly the details of "libATA"
> and all but what bothers me more is somehow spelled in the original
> question, why the quiet
> "... transition to 2.6.28 changing the 'view' ...".
> True, my problems of having to change from hdx to sdx don't amount
> to a hill of beans in this crazy world but in our "little" universe
> of Linux where according to folklore the average user is still at
> 386SX and 256kB (P)ATA drives, this "transition" certainly appears
> considerably a bigger event than some commits - while perfectly
> honorable - like "sata_nv: fix generic, nf2/3 detection regression".
>
> 4.1. As noted, some LFS folks should be at 2.6.27.8.
> A sub-question would then be, how come nobody got hit with this
> "transition".  Could they perchance be all pure-SATA?  Or diskless?
> Have I missed  another relevant support thread?
>
> Thanks again for your helpful comments.
> -- Alex


The transition happened long ago (I would probably guess 2.6.10, or
.15.  I do not recall.  Perhaps even earlier).  What the linux people
decided at the time was that they did not want to support 2 API's for
harddrive controllers.  SCSI and PATA.

SATA devices were added as SCSI drivers, and they also ported over
most (if not all) of the PATA drivers over to the SCSI subsystem.

There was also a decision to leave the legacy PATA code in.  (It
works, they're just not updating it other then API changes).  I have
not noticed any of the drivers disappearing from there, albet I am not
following this.

About the only change to the enduser, is that instead of hda/hdb/hdc,
they have sda/sdb/sdc, and perhaps a few more features/stability that
did not exist with the old drivers.

You may be able to get your old behavior back, if you use menuconfig
to enable the PATA subsystem, and disable the SCSI SIS driver.



the names I use above may not be 100% correct (Kernel's menu calls the
main storage subsystem driver SCSI, so I used that above), and I did
use a few assumptions.



-- 
Nathan Coulson (conathan)
------
Location: Brittish Columbia, Canada
Timezone: PST (-8)
Webpage: http://www.nathancoulson.com



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