| Message ID | 4A54FE96.2030407@marcansoft.com (mailing list archive) |
|---|---|
| State | RFC, archived |
| Delegated to: | Zhang Rui |
| Headers | show |
On Thu, 2009-07-09 at 04:16 +0800, Hector Martin wrote: > Validate the result of the _BQC or _BCQ method when querying the current > backlight level. If the value is out of range, the support for this > method is disabled. This does not break functionality as long as the > hardware doesn't touch the backlight level on it own, since the driver > will just use the last cached value. > > Acer Aspire 8930G with BIOS v1.10 (latest) has this issue. > > Signed-off-by: Hector Martin <hector@marcansoft.com> > --- linux-2.6.30/drivers/acpi/video.c 2009-07-08 22:04:54.000000000 +0200 > +++ linux-2.6.30-mod/drivers/acpi/video.c 2009-07-08 22:12:19.000000000 +0200 > @@ -602,15 +605,29 @@ acpi_video_device_lcd_get_level_current( > NULL, level); > if (ACPI_SUCCESS(status)) { > if (device->brightness->flags._BQC_use_index) { > + if (*level >= (device->brightness->count - 2)) { > + ACPI_WARNING((AE_INFO, > + "%s is broken (returned %llu)", > + buf, *level)); > + device->cap._BQC = device->cap._BCQ = 0; > + *level = device->brightness->curr; > + return 0; > + } > if (device->brightness->flags._BCL_reversed) > *level = device->brightness->count > - 3 - (*level); > *level = device->brightness->levels[*level + 2]; > > } > - *level += bqc_offset_aml_bug_workaround; > - device->brightness->curr = *level; > - return 0; > + if (*level > 100) { > + ACPI_WARNING((AE_INFO, "%s is broken " > + "(returned %llu)", buf, *level)); _BQC returns a value larger than 100? is this true on your laptop? thanks, rui > + device->cap._BQC = device->cap._BCQ = 0; > + } else { > + *level += bqc_offset_aml_bug_workaround; > + device->brightness->curr = *level; > + return 0; > + } > } else { > /* Fixme: > * should we return an error or ignore this failure? > > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Zhang Rui wrote: > _BQC returns a value larger than 100? > is this true on your laptop? Yes, it returns random garbage. It is completely broken. There's an if() in the ASL that disables the entire method (including no valid return value) when a certain EC SRAM register is 0. The backlight code also constantly clears this register. I suppose the EC should theoretically set it at some point, but it doesn't (at least not reliably). In any case, _BQC isn't needed here since the hardware doesn't change the screen brightness autonomously, and disabling the method as soon as it misbehaves works just fine.
--- linux-2.6.30/drivers/acpi/video.c 2009-07-08 22:04:54.000000000 +0200 +++ linux-2.6.30-mod/drivers/acpi/video.c 2009-07-08 22:12:19.000000000 +0200 @@ -602,15 +605,29 @@ acpi_video_device_lcd_get_level_current( NULL, level); if (ACPI_SUCCESS(status)) { if (device->brightness->flags._BQC_use_index) { + if (*level >= (device->brightness->count - 2)) { + ACPI_WARNING((AE_INFO, + "%s is broken (returned %llu)", + buf, *level)); + device->cap._BQC = device->cap._BCQ = 0; + *level = device->brightness->curr; + return 0; + } if (device->brightness->flags._BCL_reversed) *level = device->brightness->count - 3 - (*level); *level = device->brightness->levels[*level + 2]; } - *level += bqc_offset_aml_bug_workaround; - device->brightness->curr = *level; - return 0; + if (*level > 100) { + ACPI_WARNING((AE_INFO, "%s is broken " + "(returned %llu)", buf, *level)); + device->cap._BQC = device->cap._BCQ = 0; + } else { + *level += bqc_offset_aml_bug_workaround; + device->brightness->curr = *level; + return 0; + } } else { /* Fixme: * should we return an error or ignore this failure?
Validate the result of the _BQC or _BCQ method when querying the current backlight level. If the value is out of range, the support for this method is disabled. This does not break functionality as long as the hardware doesn't touch the backlight level on it own, since the driver will just use the last cached value. Acer Aspire 8930G with BIOS v1.10 (latest) has this issue. Signed-off-by: Hector Martin <hector@marcansoft.com>