Re: What's in libata-dev.git

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Alan Cox wrote:

>>>drivers/ide. You might want to do 256 for SATA Jeff but please don't do
>>>256 for PATA. Reading specs is too hard for some people ;)

>>>Some drives abort the xfer, some just choked.

>>Where in drivers/ide is it limited to 255?

> Being a sensible sanity check it was removed, and that was a small
> mistake. Some 2.4 also has a 256 limit and it broken various transparent
> raid units, older Maxtors(1Gb or so), some IBM drives etc. Got fixed in
> -ac but never in base.

> The failure pattern is pretty ugly too, your box runs and runs and
> eventually you get a linear 256 sector I/O and it all blows up,
> sometimes. The IBM's abort the xfer but the maxtors may or may not get
> it right (its as if half the firmware has the right test).

    So, this seems to have a long history... :-)
    I've also heard several years ago of the drives not getting anything over 
128 sectors right, but those should be really brain-damaged...

> We could perhaps do it by ATA version - 255 for ATA < 3 256 for ATA 3+,

    Wouldn't work, I'm afraid. That IBM drive is UltraATA/33, so no less than 
ATA-4...
    Well, after having referred to the ID data read from it, it's ATA-3 actually.

> lots for LBA48 ? Thats assuming you can show 256 sectors is faster than
> 255. I'd bet for normal I/O its unmeasurably small.

> Alan

WBR, Sergei