Long time ago, Linux EC driver won't probe DSDT EC during boot. It was added by the following commit (see link #1 for bug report): Commit: c5279dee26c0e8d7c4200993bfc4b540d2469598 Subject: ACPI: EC: Add some basic check for ECDT data This is wrong as the only way to know if the DSDT EC is valid is to evaluate its _STA control method, but it's not proper to evaluate this control method that early and out of the ACPI enumeration process. But after we reverted back to the expected behavior, someone reported regressions (see link #2 for reference). That forced us to restore the wrong behavior back. Now we've been reported 3rd functional breakage, the only way to fix it is to evaluate _STA (see link #3 for newer requirement). And the safest way of evaluating _STA is to do that during Linux ACPI device enumeration. As the link #2 reported issue is not fatal, we could still skip boot stage DSDT probe. But in order not to trigger regressions, this patch just introduces a boot parameter instead of unconditionally changing the upstreamed behavior. Link: http://bugzilla.kernel.org/show_bug.cgi?id=11880 [#1] Link: http://bugzilla.kernel.org/show_bug.cgi?id=119261 [#2] Link: http://bugzilla.kernel.org/show_bug.cgi?id=195651 [#3] Tested-by: Daniel Drake <drake@xxxxxxxxxxxx> Signed-off-by: Lv Zheng <lv.zheng@xxxxxxxxx> --- drivers/acpi/ec.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c index a920db6..a7e74ae 100644 --- a/drivers/acpi/ec.c +++ b/drivers/acpi/ec.c @@ -151,6 +151,10 @@ static bool ec_freeze_events __read_mostly = true; module_param(ec_freeze_events, bool, 0644); MODULE_PARM_DESC(ec_freeze_events, "Disabling event handling during suspend/resume"); +static bool ec_no_dsdt_boot_ec __read_mostly = false; +module_param(ec_no_dsdt_boot_ec, bool, 0644); +MODULE_PARM_DESC(ec_no_dsdt_boot_ec, "Do not probe DSDT EC as boot EC"); + struct acpi_ec_query_handler { struct list_head node; acpi_ec_query_func func; @@ -1679,6 +1683,9 @@ int __init acpi_ec_dsdt_probe(void) struct acpi_ec *ec; int ret; + if (ec_no_dsdt_boot_ec) + return -ENODEV; + ec = acpi_ec_alloc(); if (!ec) return -ENOMEM; -- 2.7.4 -- 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
