I've tripped over some devices that work with PNPBIOS but not with
PNPACPI, even though Linux is configuring the devices identically.
Linux evaluates _CRS to get a template, which it then fills in and
passes to _SRS to configure the device. The ACPI CA decodes the AML
bytestream returned from _CRS into a series of acpi_resource structs.
When Linux evaluates _SRS, the ACPI CA re-encodes the acpi_resource
structs into an AML bytestream. However, the encoded bytestream
sometimes has a different form than that returned from _CRS.
For example, acpi_rs_set_irq encodes a small IRQ descriptor. If the
IRQ is edge-sensitive, active high, and exclusive, acpi_rs_set_irq
optimizes the output AML by omitting the optional flags byte.
I think it would be better for acpi_rs_set_irq to generate an AML
descriptor that exactly matches the format and size of the descriptor
we got from _CRS because _SRS may not be smart enough to handle the
variation.
On a Toshiba Portege 4000, the parport_pc and smsc-ircc2 drivers both
work with PNPBIOS, and neither works with PNPACPI. I think the reason
is this acpi_rs_set_irq optimization. If I apply the attached patch,
which removes that optimization, both drivers work with PNPACPI.
I don't claim that this patch is correct, because it *always* generates
3-byte IRQ descriptors, while _SRS may be expecting a 2-byte descriptor.
But I think it is enough to point out a problem.
Bjorn
Index: work10/drivers/acpi/resources/rsirq.c
===================================================================
--- work10.orig/drivers/acpi/resources/rsirq.c 2008-05-21 15:14:10.000000000 -0600
+++ work10/drivers/acpi/resources/rsirq.c 2008-05-21 15:15:11.000000000 -0600
@@ -152,26 +152,6 @@ struct acpi_rsconvert_info acpi_rs_set_i
/* Reset length to 3 bytes (descriptor with flags byte) */
{ACPI_RSC_LENGTH, 0, 0, sizeof(struct aml_resource_irq)},
-
- /*
- * Check if the flags byte is necessary. Not needed if the flags are:
- * ACPI_EDGE_SENSITIVE, ACPI_ACTIVE_HIGH, ACPI_EXCLUSIVE
- */
- {ACPI_RSC_EXIT_NE, ACPI_RSC_COMPARE_VALUE,
- ACPI_RS_OFFSET(data.irq.triggering),
- ACPI_EDGE_SENSITIVE},
-
- {ACPI_RSC_EXIT_NE, ACPI_RSC_COMPARE_VALUE,
- ACPI_RS_OFFSET(data.irq.polarity),
- ACPI_ACTIVE_HIGH},
-
- {ACPI_RSC_EXIT_NE, ACPI_RSC_COMPARE_VALUE,
- ACPI_RS_OFFSET(data.irq.sharable),
- ACPI_EXCLUSIVE},
-
- /* We can optimize to a 2-byte irq_no_flags() descriptor */
-
- {ACPI_RSC_LENGTH, 0, 0, sizeof(struct aml_resource_irq_noflags)}
};
/*******************************************************************************
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
