Re: [PATCH 4/4] platform/chrome: i2c: i2c-cros-ec-tunnel: Convert i2c tunnel to MFD Cell

[Guenter Roeck <groeck@google.com>]

On Thu, Nov 21, 2019 at 1:11 PM Raul E Rangel <rrangel@chromium.org> wrote:
>
> If the i2c-cros-ec-tunnel driver is compiled into the kernel, it is
> possible that i2c-cros-ec-tunnel could be probed before cros_ec_XXX
> has finished initializing and setting the drvdata. This would cause a
> NULL pointer panic.
>
> Converting this driver over to an MFD solves the problem and aligns with
> where the cros_ec is going.
>

I thought the mfd maintainer objects to the use of the mfd API outside
drivers/mfd. Did that change recently ?

Guenter

> Signed-off-by: Raul E Rangel <rrangel@chromium.org>
> ---
> You can now see the device node lives under the mfd device.
>
> $ find /sys/bus/platform/devices/cros-ec-dev.0.auto/cros-ec-i2c-tunnel.12.auto/ -iname firmware_node -exec ls -l '{}' \;
> /sys/bus/platform/devices/cros-ec-dev.0.auto/cros-ec-i2c-tunnel.12.auto/firmware_node -> ../../../../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:1c/PNP0C09:00/GOOG0004:00/GOOG0012:00
> /sys/bus/platform/devices/cros-ec-dev.0.auto/cros-ec-i2c-tunnel.12.auto/i2c-9/firmware_node -> ../../../../../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:1c/PNP0C09:00/GOOG0004:00/GOOG0012:00
> /sys/bus/platform/devices/cros-ec-dev.0.auto/cros-ec-i2c-tunnel.12.auto/i2c-9/i2c-10EC5682:00/firmware_node -> ../../../../../../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:1c/PNP0C09:00/GOOG0004:00/GOOG0012:00/10EC5682:00
>
>  drivers/i2c/busses/i2c-cros-ec-tunnel.c | 36 +++++++++----------------
>  drivers/mfd/cros_ec_dev.c               | 19 +++++++++++++
>  2 files changed, 32 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-cros-ec-tunnel.c b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> index 5d91e33eb600..2e3217678fa3 100644
> --- a/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> +++ b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> @@ -6,6 +6,7 @@
>  #include <linux/acpi.h>
>  #include <linux/module.h>
>  #include <linux/i2c.h>
> +#include <linux/mfd/cros_ec.h>
>  #include <linux/platform_data/cros_ec_commands.h>
>  #include <linux/platform_data/cros_ec_proto.h>
>  #include <linux/platform_device.h>
> @@ -27,7 +28,6 @@
>  struct ec_i2c_device {
>         struct device *dev;
>         struct i2c_adapter adap;
> -       struct cros_ec_device *ec;
>
>         u16 remote_bus;
>
> @@ -176,6 +176,7 @@ static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
>  {
>         struct ec_i2c_device *bus = adap->algo_data;
>         struct device *dev = bus->dev;
> +       struct cros_ec_dev *ec = dev_get_drvdata(dev->parent);
>         const u16 bus_num = bus->remote_bus;
>         int request_len;
>         int response_len;
> @@ -183,6 +184,16 @@ static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
>         int result;
>         struct cros_ec_command *msg;
>
> +       if (!ec) {
> +               dev_err(dev, "%s: ec is missing!\n", __func__);
> +               return -EINVAL;
> +       }
> +
> +       if (!ec->ec_dev) {
> +               dev_err(dev, "%s: ec->ec_dev is missing!\n", __func__);
> +               return -EINVAL;
> +       }
> +
>         request_len = ec_i2c_count_message(i2c_msgs, num);
>         if (request_len < 0) {
>                 dev_warn(dev, "Error constructing message %d\n", request_len);
> @@ -212,7 +223,7 @@ static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
>         msg->outsize = request_len;
>         msg->insize = response_len;
>
> -       result = cros_ec_cmd_xfer_status(bus->ec, msg);
> +       result = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
>         if (result < 0) {
>                 dev_err(dev, "Error transferring EC i2c message %d\n", result);
>                 goto exit;
> @@ -241,17 +252,11 @@ static const struct i2c_algorithm ec_i2c_algorithm = {
>
>  static int ec_i2c_probe(struct platform_device *pdev)
>  {
> -       struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
>         struct device *dev = &pdev->dev;
>         struct ec_i2c_device *bus = NULL;
>         u32 remote_bus;
>         int err;
>
> -       if (!ec->cmd_xfer) {
> -               dev_err(dev, "Missing sendrecv\n");
> -               return -EINVAL;
> -       }
> -
>         bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
>         if (bus == NULL)
>                 return -ENOMEM;
> @@ -263,7 +268,6 @@ static int ec_i2c_probe(struct platform_device *pdev)
>         }
>         bus->remote_bus = remote_bus;
>
> -       bus->ec = ec;
>         bus->dev = dev;
>
>         bus->adap.owner = THIS_MODULE;
> @@ -292,25 +296,11 @@ static int ec_i2c_remove(struct platform_device *dev)
>         return 0;
>  }
>
> -static const struct of_device_id cros_ec_i2c_of_match[] = {
> -       { .compatible = "google,cros-ec-i2c-tunnel" },
> -       {},
> -};
> -MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);
> -
> -static const struct acpi_device_id cros_ec_i2c_tunnel_acpi_id[] = {
> -       { "GOOG0012", 0 },
> -       { }
> -};
> -MODULE_DEVICE_TABLE(acpi, cros_ec_i2c_tunnel_acpi_id);
> -
>  static struct platform_driver ec_i2c_tunnel_driver = {
>         .probe = ec_i2c_probe,
>         .remove = ec_i2c_remove,
>         .driver = {
>                 .name = "cros-ec-i2c-tunnel",
> -               .acpi_match_table = ACPI_PTR(cros_ec_i2c_tunnel_acpi_id),
> -               .of_match_table = of_match_ptr(cros_ec_i2c_of_match),
>         },
>  };
>
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index 1efdba18f20b..61b20e061f75 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -113,6 +113,18 @@ static const struct mfd_cell cros_ec_vbc_cells[] = {
>         { .name = "cros-ec-vbc", }
>  };
>
> +static struct mfd_cell_acpi_match cros_ec_i2c_tunnel_acpi_match = {
> +       .pnpid = "GOOG0012"
> +};
> +
> +static struct mfd_cell cros_ec_fw_cells[] = {
> +       {
> +               .name = "cros-ec-i2c-tunnel",
> +               .acpi_match = &cros_ec_i2c_tunnel_acpi_match,
> +               .of_compatible = "google,cros-ec-i2c-tunnel"
> +       },
> +};
> +
>  int cros_ec_check_features(struct cros_ec_dev *ec, int feature)
>  {
>         struct cros_ec_command *msg;
> @@ -485,6 +497,13 @@ static int ec_device_probe(struct platform_device *pdev)
>                          "failed to add cros-ec platform devices: %d\n",
>                          retval);
>
> +       retval = mfd_add_hotplug_devices(ec->dev, cros_ec_fw_cells,
> +                                        ARRAY_SIZE(cros_ec_fw_cells));
> +       if (retval)
> +               dev_warn(ec->dev,
> +                        "failed to add cros-ec fw platform devices: %d\n",
> +                        retval);
> +
>         /* Check whether this EC instance has a VBC NVRAM */
>         node = ec->ec_dev->dev->of_node;
>         if (of_property_read_bool(node, "google,has-vbc-nvram")) {
> --
> 2.24.0.432.g9d3f5f5b63-goog
>