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    SubjectRe: [PATCH v5] mfd: cros_ec_dev: Register cros_ec_accel_legacy driver as a subdevice
    On Mon, Apr 1, 2019 at 8:46 PM Lee Jones <lee.jones@linaro.org> wrote:
    >
    > On Wed, 27 Feb 2019, Gwendal Grignou wrote:
    >
    > > From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
    > >
    > > 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 <gwendal@chromium.org>
    > > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
    > > Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
    > > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
    > > ---
    > > Changes in v5:
    > > - Remove unnecessary white lines.
    > >
    > > Changes in v4:
    > > - [5/8] Nit: EC -> ECs (Lee Jones)
    > > - [5/8] Statically define cros_ec_accel_legacy_cells (Lee Jones)
    > >
    > > Changes in v3:
    > > - [5/8] Add the Reviewed-by Andy Shevchenko.
    > >
    > > Changes in v2:
    > > - [5/8] Add the Reviewed-by Gwendal.
    > >
    > > drivers/mfd/cros_ec_dev.c | 66 +++++++++++++++++++++++++++++++++++++++
    > > 1 file changed, 66 insertions(+)
    > >
    > > diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
    > > index d275deaecb12..64567bd0a081 100644
    > > --- a/drivers/mfd/cros_ec_dev.c
    > > +++ b/drivers/mfd/cros_ec_dev.c
    > > @@ -376,6 +376,69 @@ static void cros_ec_sensors_register(struct cros_ec_dev *ec)
    > > kfree(msg);
    > > }
    > >
    > > +static struct cros_ec_sensor_platform sensor_platforms[] = {
    > > + { .sensor_num = 0 },
    > > + { .sensor_num = 1 }
    > > +};
    >
    > I'm still very uncomfortable with this struct.
    >
    > Other than these indices, the sensors have no other distinguishing
    > features, thus there should be no need to identify or distinguish
    > between them in this way.
    When initializing the sensors, the IIO driver expect to find in the
    data structure pointed by dev_get_platdata(dev), in field sensor_num
    is stored the index assigned by the embedded controller to talk to a
    given sensor.
    cros_ec_sensors_register() use the same mechanism; in that function,
    the sensor_num field is populated from the output of an EC command
    MOTIONSENSE_CMD_INFO. In case of legacy mode, that command may not be
    available and in any case we know the EC has only either 2
    accelerometers present or nothing.

    For instance, let's compare a legacy device with a more recent one:

    legacy:
    type | id | sensor_num | device name
    accelerometer | 0 | 0 | cros-ec-accel.0
    accelerometer | 1 | 1 | cros-ec-accel.1

    Modern:
    type | id | sensor_num | device name
    accelerometer | 0 | 0 | cros-ec-accel.0
    accelerometer | 1 | 1 | cros-ec-accel.1
    gyroscope | 0 | 2 | cros-ec-gyro.0
    magnetometer | 0 | 3 | cros-ec-mag.0
    light | 0 | 4 | cros-ec-light.0
    ...

    Gwendal.

    >
    > > +static const struct mfd_cell cros_ec_accel_legacy_cells[] = {
    > > + {
    > > + .name = "cros-ec-accel-legacy",
    > > + .id = 0,
    > > + .platform_data = &sensor_platforms[0],
    > > + .pdata_size = sizeof(struct cros_ec_sensor_platform),
    > > + },
    > > + {
    > > + .name = "cros-ec-accel-legacy",
    > > + .id = 1,
    > > + .platform_data = &sensor_platforms[1],
    > > + .pdata_size = sizeof(struct cros_ec_sensor_platform),
    > > + }
    > > +};
    > > +
    > > +static void cros_ec_accel_legacy_register(struct cros_ec_dev *ec)
    > > +{
    > > + struct cros_ec_device *ec_dev = ec->ec_dev;
    > > + u8 status;
    > > + int ret;
    > > +
    > > + /*
    > > + * ECs 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
    > > + */
    > > + ret = mfd_add_devices(ec->dev, PLATFORM_DEVID_AUTO,
    >
    > Using PLATFORM_DEVID_AUTO whilst providing the MFD cells with IDs
    > doesn't make any sense. Please remove the IDs from the cells.
    Removed in V6.
    >
    > > + cros_ec_accel_legacy_cells,
    > > + ARRAY_SIZE(cros_ec_accel_legacy_cells),
    > > + NULL, 0, NULL);
    > > + if (ret)
    > > + dev_err(ec_dev->dev, "failed to add EC sensors\n");
    > > +}
    > > +
    > > static const struct mfd_cell cros_ec_cec_cells[] = {
    > > { .name = "cros-ec-cec" }
    > > };
    > > @@ -437,6 +500,9 @@ 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 CEC host command support */
    > > if (cros_ec_check_features(ec, EC_FEATURE_CEC)) {
    >
    > --
    > Lee Jones [李琼斯]
    > Linaro Services Technical Lead
    > Linaro.org │ Open source software for ARM SoCs
    > Follow Linaro: Facebook | Twitter | Blog

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