With this patch, the cros_ec_ctl driver will register the legacy
accelerometer driver (named cros_ec_accel_legacy) if it fails to
register sensors through the usual path cros_ec_sensors_register().
This legacy device is present on Chromebook devices with older EC
firmware only supporting deprecated EC commands (Glimmer based devices).

Tested-by: Gwendal Grignou <gwen...@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balle...@collabora.com>
---
 drivers/mfd/cros_ec_dev.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
index e0c604ab380f..fc98e0564061 100644
--- a/drivers/mfd/cros_ec_dev.c
+++ b/drivers/mfd/cros_ec_dev.c
@@ -389,6 +389,63 @@ static void cros_ec_sensors_register(struct cros_ec_dev 
*ec)
        kfree(msg);
 }
 
+#define CROS_EC_SENSOR_LEGACY_NUM 2
+static struct mfd_cell cros_ec_accel_legacy_cells[CROS_EC_SENSOR_LEGACY_NUM];
+
+static void cros_ec_accel_legacy_register(struct cros_ec_dev *ec)
+{
+       struct cros_ec_device *ec_dev = ec->ec_dev;
+       u8 status;
+       int i, ret;
+       struct cros_ec_sensor_platform
+               sensor_platforms[CROS_EC_SENSOR_LEGACY_NUM];
+
+       /*
+        * EC that need legacy support are the main EC, directly connected to
+        * the AP.
+        */
+       if (ec->cmd_offset != 0)
+               return;
+
+       /*
+        * Check if EC supports direct memory reads and if EC has
+        * accelerometers.
+        */
+       if (!ec_dev->cmd_readmem)
+               return;
+
+       ret = ec_dev->cmd_readmem(ec_dev, EC_MEMMAP_ACC_STATUS, 1, &status);
+       if (ret < 0) {
+               dev_warn(ec->dev, "EC does not support direct reads.\n");
+               return;
+       }
+
+       /* Check if EC has accelerometers. */
+       if (!(status & EC_MEMMAP_ACC_STATUS_PRESENCE_BIT)) {
+               dev_info(ec->dev, "EC does not have accelerometers.\n");
+               return;
+       }
+
+       /*
+        * Register 2 accelerometers
+        */
+       for (i = 0; i < CROS_EC_SENSOR_LEGACY_NUM; i++) {
+               cros_ec_accel_legacy_cells[i].name = "cros-ec-accel-legacy";
+               sensor_platforms[i].sensor_num = i;
+               cros_ec_accel_legacy_cells[i].id = i;
+               cros_ec_accel_legacy_cells[i].platform_data =
+                       &sensor_platforms[i];
+               cros_ec_accel_legacy_cells[i].pdata_size =
+                       sizeof(struct cros_ec_sensor_platform);
+       }
+       ret = mfd_add_devices(ec->dev, PLATFORM_DEVID_AUTO,
+                             cros_ec_accel_legacy_cells,
+                             CROS_EC_SENSOR_LEGACY_NUM,
+                             NULL, 0, NULL);
+       if (ret)
+               dev_err(ec_dev->dev, "failed to add EC sensors\n");
+}
+
 static const struct mfd_cell cros_ec_rtc_cell = {
        .name = "cros-ec-rtc",
 };
@@ -440,6 +497,9 @@ static int ec_device_probe(struct platform_device *pdev)
        /* check whether this EC is a sensor hub. */
        if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE))
                cros_ec_sensors_register(ec);
+       else
+               /* Workaroud for older EC firmware */
+               cros_ec_accel_legacy_register(ec);
 
        /* check whether this EC instance has RTC host command support */
        if (cros_ec_check_features(ec, EC_FEATURE_RTC)) {
-- 
2.16.1

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