Re: Display/APM problems on Toshiba laptops

David Luyer (luyer@ucs.uwa.edu.au)
Wed, 10 Feb 1999 11:59:36 +0800


> On my toshiba 730CDT (ct65550 video chipset) you are supposed to be
> able to flip between the internal TFT display and an external monitor
> using the Fn-F5 hotkey. This stopped working properly when I upgraded
> to 2.0.36 or 2.2.0. 2.0.35 is fine.

(code below is from arch/i386/kernel/apm.c)

A change in 2.2.1 may affect the problem you went on to describe,
you might want to try it. For another idea, read on.

The possible change which might be affecting you is to do with display
blanking.

2.2.0 uses device 0x0100 only. 2.2.1 tries to be smart. Earlier kernels
(like 2.0.35) used 0x01ff. (Toshiba Libretto 70CT with a ct65XXXX needs
0x01ff, I think it's a BIOS bug.)

>From 2.2.1:

#ifdef CONFIG_APM_DISPLAY_BLANK
/* Called by apm_display_blank and apm_display_unblank when apm_enabled. */
static int apm_set_display_power_state(u_short state)
{
int error;

/* Blank the first display device */
error = set_power_state(0x0100, state);
if (error == APM_BAD_DEVICE)
/* try to blank them all instead */
error = set_power_state(0x01ff, state);
return error;
}
#endif

(1) see if this works (you didn't indicate you'd tried 2.2.1)
(2) see if it works if you just revert to the old

#ifdef CONFIG_APM_DISPLAY_BLANK
/* Called by apm_display_blank and apm_display_unblank when apm_enabled. */
static int apm_set_display_power_state(u_short state)
{
int error;

/* Blank the first display device */
error = set_power_state(0x01ff, state);
return error;
}
#endif

If (1) works, be happy.
If (2) works but (1) doesn't, inform the relevant maintainer
(and I'd like to know too :-).
If neither work, good luck finding the problem...

David.

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