[PATCH] platform/chrome: cros_ec_lpc: do not try DMI match when ACPI device found

[PATCH] platform/chrome: cros_ec_lpc: do not try DMI match when ACPI device found

[Dmitry Torokhov]

Older models of Chromebooks did not describe the LPC EC in their ACPI
tables; starting with Strago-based devices Google is using GOOG0004 device
to describe EC LPC.

DMI-based match is fragile and does not work reliably, especially when
using custom firmware. It is also not needed when we can locate the right
ACPI device, so let's stop bailing out when DMI does not match but the
right ACPI device is present.

Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/platform/chrome/cros_ec_lpc.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
index af89e82eecd23..a000d2fbbb0be 100644
--- a/drivers/platform/chrome/cros_ec_lpc.c
+++ b/drivers/platform/chrome/cros_ec_lpc.c
@@ -419,7 +419,13 @@ static int __init cros_ec_lpc_init(void)
 	int ret;
 	acpi_status status;
 
-	if (!dmi_check_system(cros_ec_lpc_dmi_table)) {
+	status = acpi_get_devices(ACPI_DRV_NAME, cros_ec_lpc_parse_device,
+				  &cros_ec_lpc_acpi_device_found, NULL);
+	if (ACPI_FAILURE(status))
+		pr_warn(DRV_NAME ": Looking for %s failed\n", ACPI_DRV_NAME);
+
+	if (!cros_ec_lpc_acpi_device_found &&
+	    !dmi_check_system(cros_ec_lpc_dmi_table)) {
 		pr_err(DRV_NAME ": unsupported system.\n");
 		return -ENODEV;
 	}
@@ -434,11 +440,6 @@ static int __init cros_ec_lpc_init(void)
 		return ret;
 	}
 
-	status = acpi_get_devices(ACPI_DRV_NAME, cros_ec_lpc_parse_device,
-				  &cros_ec_lpc_acpi_device_found, NULL);
-	if (ACPI_FAILURE(status))
-		pr_warn(DRV_NAME ": Looking for %s failed\n", ACPI_DRV_NAME);
-
 	if (!cros_ec_lpc_acpi_device_found) {
 		/* Register the device, and it'll get hooked up automatically */
 		ret = platform_device_register(&cros_ec_lpc_device);
-- 
2.17.0.441.gb46fe60e1d-goog


-- 
Dmitry

Re: [PATCH] platform/chrome: cros_ec_lpc: do not try DMI match when ACPI device found

[Benson Leung]

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Hi Dmitry,

On Tue, May 22, 2018 at 04:08:41PM -0700, Dmitry Torokhov wrote:
> Older models of Chromebooks did not describe the LPC EC in their ACPI
> tables; starting with Strago-based devices Google is using GOOG0004 device
> to describe EC LPC.
> 
> DMI-based match is fragile and does not work reliably, especially when
> using custom firmware. It is also not needed when we can locate the right
> ACPI device, so let's stop bailing out when DMI does not match but the
> right ACPI device is present.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Nice fix. Applied. 

Thanks,
Benson

-- 
Benson Leung
Staff Software Engineer
Chrome OS Kernel
Google Inc.
bleung@google.com
Chromium OS Project
bleung@chromium.org

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