Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Robert Hancock]

Al Boldi wrote:
> Alan Cox wrote:
>>> Wow!  I have been running 80wire cable detection override on 40wire
>>> cables for quite some time without any problem, but I never thought it
>>> to be legal if the 40wire cable length is short enough.
>> Yes.
>>
>>> How short does it have to be, and can't we have a kernel bootparm to
>>> override the cable detection?
>> For most users the goal should be to automate behaviour. It should just
>> work.
> 
> What's the max length of a 40wire cable to sustain 80wire cable 
> characteristics?

This is normally only the case on a laptop, where the cable is 
essentially just a tiny stub between the motherboard and the drive. I 
suspect this is something that the system manufacturer has to validate 
works properly, more than any hard and fast limit.

For a normal desktop PC, it would be far better to just use an 80-wire 
cable.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Al Boldi]

Alan Cox wrote:
> Daniel Exner <dex@dragonslave.de> wrote:
>> Attached patch will add above mentioned Laptop Model to whitelist for both 
>> pata_ali and alim15x3, as it is correctly detected as 40-wire connected
>> but this cable is short enough to still do transfers higher than UDMA33.
>
> Looks good to me - does need a Signed-off-by: line however

Wow!  I have been running 80wire cable detection override on 40wire cables 
for quite some time without any problem, but I never thought it to be legal 
if the 40wire cable length is short enough.

How short does it have to be, and can't we have a kernel bootparm to override 
the cable detection?


Thanks!

--
Al

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Alan Cox]

> Wow!  I have been running 80wire cable detection override on 40wire cables 
> for quite some time without any problem, but I never thought it to be legal 
> if the 40wire cable length is short enough.

Yes.

> How short does it have to be, and can't we have a kernel bootparm to override 
> the cable detection?

For most users the goal should be to automate behaviour. It should just
work.

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Al Boldi]

Alan Cox wrote:
> > Wow!  I have been running 80wire cable detection override on 40wire
> > cables for quite some time without any problem, but I never thought it
> > to be legal if the 40wire cable length is short enough.
>
> Yes.
>
> > How short does it have to be, and can't we have a kernel bootparm to
> > override the cable detection?
>
> For most users the goal should be to automate behaviour. It should just
> work.

What's the max length of a 40wire cable to sustain 80wire cable 
characteristics?


Thanks!

--
Al

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Jan Engelhardt]

On Aug 30 2007 16:54, Al Boldi wrote:
>
>What's the max length of a 40wire cable to sustain 80wire cable 
>characteristics?

Hard to tell, since some (most?) laptops have sort of a backplane and there
might be no real cable you could see because it's all mainboard wire paths
already.


	Jan
-- 

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Lennart Sorensen]

On Thu, Aug 30, 2007 at 09:38:23PM +0200, Jan Engelhardt wrote:
> Hard to tell, since some (most?) laptops have sort of a backplane and there
> might be no real cable you could see because it's all mainboard wire paths
> already.

Makes you wonder why the mainboard doesn't just pretend to be an 80 wire
cable if that is what it is compatible with.  Seems like a design flaw
in the laptop to not do so.

--
Len Sorensen

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Jan Engelhardt]

On Aug 30 2007 15:47, Lennart Sorensen wrote:
>On Thu, Aug 30, 2007 at 09:38:23PM +0200, Jan Engelhardt wrote:
>> Hard to tell, since some (most?) laptops have sort of a backplane and there
>> might be no real cable you could see because it's all mainboard wire paths
>> already.
>
>Makes you wonder why the mainboard doesn't just pretend to be an 80 wire
>cable if that is what it is compatible with.  Seems like a design flaw
>in the laptop to not do so.

Or lazyness on behalf the vendor. You know, some even don't fix their DSDT...


	Jan
-- 

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Alan Cox]

> What's the max length of a 40wire cable to sustain 80wire cable 
> characteristics?

Depends on the materials and connector. The required electrical
characteristics for any cable are in the spec, and if you want to know
more you'll need to know a lot more than I do about transmission line
theory!

[PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Daniel Exner]

[-- Attachment #1: Type: text/plain, Size: 469 bytes --]

Hi!

Please CC me, as I'm currently not subscribed to this list, thx.

Attached patch will add above mentioned Laptop Model to whitelist for both 
pata_ali and alim15x3, as it is correctly detected as 40-wire connected but 
this cable is short enough to still do transfers higher than UDMA33.
Don't know if this is also true for other S1800 Laptops cause I own only one.

I hope I did this correctly as this is my first Patch Mail to LKML :)
-- 
Greetings
Daniel Exner

[-- Attachment #2: patchAli_pata.patch --]
[-- Type: text/x-diff, Size: 840 bytes --]

--- linux-2.6.22.old/drivers/ata/pata_ali.c	2007-08-29 23:27:53.000000000 +0200
+++ linux-2.6.22/drivers/ata/pata_ali.c	2007-08-29 23:14:37.000000000 +0200
@@ -48,6 +48,13 @@
 			DMI_MATCH(DMI_BOARD_VERSION, "OmniBook N32N-736"),
 		},
 	},
+	{
+		.ident = "Toshiba Satelite S1800-814",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "S1800-814"),
+		},
+	}, 
 	{ }
 };
 
--- linux-2.6.22.old/drivers/ide/pci/alim15x3.c	2007-08-29 22:17:14.000000000 +0200
+++ linux-2.6.22/drivers/ide/pci/alim15x3.c	2007-08-29 22:56:27.000000000 +0200
@@ -596,6 +596,13 @@
 			DMI_MATCH(DMI_BOARD_VERSION, "OmniBook N32N-736"),
 		},
 	},
+	{
+		.ident = "Toshiba Satellite S1800-814",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "S1800-814"),
+		},
+	},
 	{ }
 };
 

Re: [PATCH] Override 80-wire cable detection for Toshiba S1800-814

[Alan Cox]

On Wed, 29 Aug 2007 23:41:13 +0200
Daniel Exner <dex@dragonslave.de> wrote:

> Hi!
> 
> Please CC me, as I'm currently not subscribed to this list, thx.
> 
> Attached patch will add above mentioned Laptop Model to whitelist for both 
> pata_ali and alim15x3, as it is correctly detected as 40-wire connected but 
> this cable is short enough to still do transfers higher than UDMA33.
> Don't know if this is also true for other S1800 Laptops cause I own only one.

Looks good to me - does need a Signed-off-by: line however