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Subject: Re: [PATCH v2] platform/chrome: Don't populate lightbar device if it
 isn't there
To:     Guenter Roeck <groeck@google.com>,
        Stephen Boyd <swboyd@chromium.org>
Cc:     Benson Leung <bleung@chromium.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Gwendal Grignou <gwendal@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        Lee Jones <lee.jones@linaro.org>
References: <20200909224226.2177401-1-swboyd@chromium.org>
 <CABXOdTeWfuZHLywMU1d+No-NSZ4uusAgkhs=2hNZGFM-uYz2wA@mail.gmail.com>
From:   Enric Balletbo i Serra <enric.balletbo@collabora.com>
Message-ID: <c3ba5d92-8bfe-30d7-44f0-c8a3e40d1906@collabora.com>
Date:   Thu, 10 Sep 2020 16:32:31 +0200
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Hi,

On 10/9/20 16:18, Guenter Roeck wrote:
> On Wed, Sep 9, 2020 at 3:42 PM Stephen Boyd <swboyd@chromium.org> wrote:
>>
>> The cros ec lightbar driver has a check in probe to fail early if the ec
>> device isn't the cros_ec one or if it can't read the lightbar version
>> from the EC. Let's move this check to the place where the lightbar
>> device is registered. This way we don't expose devices that aren't
>> actually there on devices that don't have a lightbar.
>>
>> This should improve memory and possibly performance too because struct
>> devices don't exactly have a small memory footprint and they contribute
>> to suspend/resume regardless of driver attachment.
>>
>> Cc: Gwendal Grignou <gwendal@chromium.org>
>> Cc: Guenter Roeck <groeck@chromium.org>
>> Cc: Lee Jones <lee.jones@linaro.org>
>> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
>> ---
>>
>> Changes from v1:
>>  * Rebased on linux-next patches to this file
>>
>>  drivers/mfd/cros_ec_dev.c                   |  16 ++-
>>  drivers/platform/chrome/cros_ec_lightbar.c  | 102 ++------------------
>>  drivers/platform/chrome/cros_ec_proto.c     |  84 ++++++++++++++++
>>  include/linux/platform_data/cros_ec_proto.h |   4 +
>>  4 files changed, 111 insertions(+), 95 deletions(-)
>>
>> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
>> index d07b43d7c761..9e98b2ec5d92 100644
>> --- a/drivers/mfd/cros_ec_dev.c
>> +++ b/drivers/mfd/cros_ec_dev.c
>> @@ -74,6 +74,10 @@ static const struct mfd_cell cros_ec_cec_cells[] = {
>>         { .name = "cros-ec-cec", },
>>  };
>>
>> +static const struct mfd_cell cros_ec_lightbar_cells[] = {
>> +       { .name = "cros-ec-lightbar", },
>> +};
>> +
>>  static const struct mfd_cell cros_ec_rtc_cells[] = {
>>         { .name = "cros-ec-rtc", },
>>  };
>> @@ -112,7 +116,6 @@ static const struct cros_feature_to_cells cros_subdevices[] = {
>>  static const struct mfd_cell cros_ec_platform_cells[] = {
>>         { .name = "cros-ec-chardev", },
>>         { .name = "cros-ec-debugfs", },
>> -       { .name = "cros-ec-lightbar", },
>>         { .name = "cros-ec-sysfs", },
>>  };
>>
>> @@ -206,6 +209,17 @@ static int ec_device_probe(struct platform_device *pdev)
>>                 }
>>         }
>>
>> +       if (!strcmp(ec_platform->ec_name, CROS_EC_DEV_NAME) &&
>> +           !cros_ec_get_lightbar_version(ec, NULL, NULL)) {
> 
> Any idea why the lightbar code doesn't use cros_ec_check_features() ?
> There is a definition for EC_FEATURE_LIGHTBAR, but it doesn't seem to
> be used. It would be much more convenient if that feature check could
> be used instead of moving the get_lightbar_version command and its
> helper function around.
> 

IIRC it was to support a very old device, the Pixel Chromebook (Link). This flag
is not set in this device but has a lightbar, hence we had this 'weird' way to
detect the lightbar.

> Thanks,
> Guenter
> 
>> +               retval = mfd_add_hotplug_devices(ec->dev,
>> +                               cros_ec_lightbar_cells,
>> +                               ARRAY_SIZE(cros_ec_lightbar_cells));
>> +               if (retval)
>> +                       dev_err(ec->dev,
>> +                               "failed to add lightbar device: %d\n",
>> +                               retval);
>> +       }
>> +
>>         /*
>>          * The PD notifier driver cell is separate since it only needs to be
>>          * explicitly added on platforms that don't have the PD notifier ACPI
>> diff --git a/drivers/platform/chrome/cros_ec_lightbar.c b/drivers/platform/chrome/cros_ec_lightbar.c
>> index de8dfb12e486..a7cfde90c8e5 100644
>> --- a/drivers/platform/chrome/cros_ec_lightbar.c
>> +++ b/drivers/platform/chrome/cros_ec_lightbar.c
>> @@ -82,77 +82,6 @@ static int lb_throttle(void)
>>         return ret;
>>  }
>>
>> -static struct cros_ec_command *alloc_lightbar_cmd_msg(struct cros_ec_dev *ec)
>> -{
>> -       struct cros_ec_command *msg;
>> -       int len;
>> -
>> -       len = max(sizeof(struct ec_params_lightbar),
>> -                 sizeof(struct ec_response_lightbar));
>> -
>> -       msg = kmalloc(sizeof(*msg) + len, GFP_KERNEL);
>> -       if (!msg)
>> -               return NULL;
>> -
>> -       msg->version = 0;
>> -       msg->command = EC_CMD_LIGHTBAR_CMD + ec->cmd_offset;
>> -       msg->outsize = sizeof(struct ec_params_lightbar);
>> -       msg->insize = sizeof(struct ec_response_lightbar);
>> -
>> -       return msg;
>> -}
>> -
>> -static int get_lightbar_version(struct cros_ec_dev *ec,
>> -                               uint32_t *ver_ptr, uint32_t *flg_ptr)
>> -{
>> -       struct ec_params_lightbar *param;
>> -       struct ec_response_lightbar *resp;
>> -       struct cros_ec_command *msg;
>> -       int ret;
>> -
>> -       msg = alloc_lightbar_cmd_msg(ec);
>> -       if (!msg)
>> -               return 0;
>> -
>> -       param = (struct ec_params_lightbar *)msg->data;
>> -       param->cmd = LIGHTBAR_CMD_VERSION;
>> -       msg->outsize = sizeof(param->cmd);
>> -       msg->result = sizeof(resp->version);
>> -       ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
>> -       if (ret < 0 && ret != -EINVAL) {
>> -               ret = 0;
>> -               goto exit;
>> -       }
>> -
>> -       switch (msg->result) {
>> -       case EC_RES_INVALID_PARAM:
>> -               /* Pixel had no version command. */
>> -               if (ver_ptr)
>> -                       *ver_ptr = 0;
>> -               if (flg_ptr)
>> -                       *flg_ptr = 0;
>> -               ret = 1;
>> -               goto exit;
>> -
>> -       case EC_RES_SUCCESS:
>> -               resp = (struct ec_response_lightbar *)msg->data;
>> -
>> -               /* Future devices w/lightbars should implement this command */
>> -               if (ver_ptr)
>> -                       *ver_ptr = resp->version.num;
>> -               if (flg_ptr)
>> -                       *flg_ptr = resp->version.flags;
>> -               ret = 1;
>> -               goto exit;
>> -       }
>> -
>> -       /* Anything else (ie, EC_RES_INVALID_COMMAND) - no lightbar */
>> -       ret = 0;
>> -exit:
>> -       kfree(msg);
>> -       return ret;
>> -}
>> -
>>  static ssize_t version_show(struct device *dev,
>>                             struct device_attribute *attr, char *buf)
>>  {
>> @@ -165,7 +94,7 @@ static ssize_t version_show(struct device *dev,
>>                 return ret;
>>
>>         /* This should always succeed, because we check during init. */
>> -       if (!get_lightbar_version(ec, &version, &flags))
>> +       if (cros_ec_get_lightbar_version(ec, &version, &flags))
>>                 return -EIO;
>>
>>         return scnprintf(buf, PAGE_SIZE, "%d %d\n", version, flags);
>> @@ -184,7 +113,7 @@ static ssize_t brightness_store(struct device *dev,
>>         if (kstrtouint(buf, 0, &val))
>>                 return -EINVAL;
>>
>> -       msg = alloc_lightbar_cmd_msg(ec);
>> +       msg = cros_ec_alloc_lightbar_cmd_msg(ec);
>>         if (!msg)
>>                 return -ENOMEM;
>>
>> @@ -222,7 +151,7 @@ static ssize_t led_rgb_store(struct device *dev, struct device_attribute *attr,
>>         unsigned int val[4];
>>         int ret, i = 0, j = 0, ok = 0;
>>
>> -       msg = alloc_lightbar_cmd_msg(ec);
>> +       msg = cros_ec_alloc_lightbar_cmd_msg(ec);
>>         if (!msg)
>>                 return -ENOMEM;
>>
>> @@ -289,7 +218,7 @@ static ssize_t sequence_show(struct device *dev,
>>         int ret;
>>         struct cros_ec_dev *ec = to_cros_ec_dev(dev);
>>
>> -       msg = alloc_lightbar_cmd_msg(ec);
>> +       msg = cros_ec_alloc_lightbar_cmd_msg(ec);
>>         if (!msg)
>>                 return -ENOMEM;
>>
>> @@ -324,7 +253,7 @@ static int lb_send_empty_cmd(struct cros_ec_dev *ec, uint8_t cmd)
>>         struct cros_ec_command *msg;
>>         int ret;
>>
>> -       msg = alloc_lightbar_cmd_msg(ec);
>> +       msg = cros_ec_alloc_lightbar_cmd_msg(ec);
>>         if (!msg)
>>                 return -ENOMEM;
>>
>> @@ -352,7 +281,7 @@ static int lb_manual_suspend_ctrl(struct cros_ec_dev *ec, uint8_t enable)
>>         struct cros_ec_command *msg;
>>         int ret;
>>
>> -       msg = alloc_lightbar_cmd_msg(ec);
>> +       msg = cros_ec_alloc_lightbar_cmd_msg(ec);
>>         if (!msg)
>>                 return -ENOMEM;
>>
>> @@ -399,7 +328,7 @@ static ssize_t sequence_store(struct device *dev, struct device_attribute *attr,
>>                         return ret;
>>         }
>>
>> -       msg = alloc_lightbar_cmd_msg(ec);
>> +       msg = cros_ec_alloc_lightbar_cmd_msg(ec);
>>         if (!msg)
>>                 return -ENOMEM;
>>
>> @@ -444,7 +373,7 @@ static ssize_t program_store(struct device *dev, struct device_attribute *attr,
>>                 return -EINVAL;
>>         }
>>
>> -       msg = alloc_lightbar_cmd_msg(ec);
>> +       msg = cros_ec_alloc_lightbar_cmd_msg(ec);
>>         if (!msg)
>>                 return -ENOMEM;
>>
>> @@ -531,24 +460,9 @@ static struct attribute_group cros_ec_lightbar_attr_group = {
>>  static int cros_ec_lightbar_probe(struct platform_device *pd)
>>  {
>>         struct cros_ec_dev *ec_dev = dev_get_drvdata(pd->dev.parent);
>> -       struct cros_ec_platform *pdata = dev_get_platdata(ec_dev->dev);
>>         struct device *dev = &pd->dev;
>>         int ret;
>>
>> -       /*
>> -        * Only instantiate the lightbar if the EC name is 'cros_ec'. Other EC
>> -        * devices like 'cros_pd' doesn't have a lightbar.
>> -        */
>> -       if (strcmp(pdata->ec_name, CROS_EC_DEV_NAME) != 0)
>> -               return -ENODEV;
>> -
>> -       /*
>> -        * Ask then for the lightbar version, if it's 0 then the 'cros_ec'
>> -        * doesn't have a lightbar.
>> -        */
>> -       if (!get_lightbar_version(ec_dev, NULL, NULL))
>> -               return -ENODEV;
>> -
>>         /* Take control of the lightbar from the EC. */
>>         lb_manual_suspend_ctrl(ec_dev, 1);
>>
>> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
>> index dda182132a6a..a08747eec36a 100644
>> --- a/drivers/platform/chrome/cros_ec_proto.c
>> +++ b/drivers/platform/chrome/cros_ec_proto.c
>> @@ -922,3 +922,87 @@ int cros_ec_get_sensor_count(struct cros_ec_dev *ec)
>>         return sensor_count;
>>  }
>>  EXPORT_SYMBOL_GPL(cros_ec_get_sensor_count);
>> +
>> +struct cros_ec_command *cros_ec_alloc_lightbar_cmd_msg(struct cros_ec_dev *ec)
>> +{
>> +       struct cros_ec_command *msg;
>> +       int len;
>> +
>> +       len = max(sizeof(struct ec_params_lightbar),
>> +                 sizeof(struct ec_response_lightbar));
>> +
>> +       msg = kmalloc(sizeof(*msg) + len, GFP_KERNEL);
>> +       if (!msg)
>> +               return NULL;
>> +
>> +       msg->version = 0;
>> +       msg->command = EC_CMD_LIGHTBAR_CMD + ec->cmd_offset;
>> +       msg->outsize = sizeof(struct ec_params_lightbar);
>> +       msg->insize = sizeof(struct ec_response_lightbar);
>> +
>> +       return msg;
>> +}
>> +EXPORT_SYMBOL_GPL(cros_ec_alloc_lightbar_cmd_msg);
>> +
>> +/**
>> + * cros_ec_get_lightbar_version() - Get the EC lightbar version
>> + *
>> + * @ec: EC device, does not have to be connected directly to the AP,
>> + *      can be daisy chained through another device.
>> + * @ver_ptr: Detected lightbar version number
>> + * @flag_ptr: Detected lightbar flags
>> + *
>> + * Call this function to determine the EC's lightbar version and flags
>> + * information. If it doesn't exist then this function returns a negative
>> + * error value.
>> + *
>> + * Return: 0 on success, negative errno on failure to detect a lightbar.
>> + */
>> +int cros_ec_get_lightbar_version(struct cros_ec_dev *ec, uint32_t *ver_ptr,
>> +                                uint32_t *flg_ptr)
>> +{
>> +       struct ec_params_lightbar *param;
>> +       struct ec_response_lightbar *resp;
>> +       struct cros_ec_command *msg;
>> +       int ret;
>> +
>> +       msg = cros_ec_alloc_lightbar_cmd_msg(ec);
>> +       if (!msg)
>> +               return -ENOMEM;
>> +
>> +       param = (struct ec_params_lightbar *)msg->data;
>> +       param->cmd = LIGHTBAR_CMD_VERSION;
>> +       msg->outsize = sizeof(param->cmd);
>> +       msg->result = sizeof(resp->version);
>> +       ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
>> +       if (ret < 0 && ret != -EINVAL)
>> +               goto exit;
>> +
>> +       switch (msg->result) {
>> +       case EC_RES_INVALID_PARAM:
>> +               /* Pixel had no version command. */
>> +               if (ver_ptr)
>> +                       *ver_ptr = 0;
>> +               if (flg_ptr)
>> +                       *flg_ptr = 0;
>> +               ret = 0;
>> +               break;
>> +       case EC_RES_SUCCESS:
>> +               resp = (struct ec_response_lightbar *)msg->data;
>> +
>> +               /* Future devices w/lightbars should implement this command */
>> +               if (ver_ptr)
>> +                       *ver_ptr = resp->version.num;
>> +               if (flg_ptr)
>> +                       *flg_ptr = resp->version.flags;
>> +               ret = 0;
>> +               break;
>> +       default:
>> +               /* Anything else (ie, EC_RES_INVALID_COMMAND) - no lightbar */
>> +               ret = -ENODEV;
>> +       }
>> +exit:
>> +       kfree(msg);
>> +       return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(cros_ec_get_lightbar_version);
>> diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
>> index 4a415ae851ef..50221254956c 100644
>> --- a/include/linux/platform_data/cros_ec_proto.h
>> +++ b/include/linux/platform_data/cros_ec_proto.h
>> @@ -229,6 +229,10 @@ u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev);
>>
>>  int cros_ec_check_features(struct cros_ec_dev *ec, int feature);
>>
>> +struct cros_ec_command *cros_ec_alloc_lightbar_cmd_msg(struct cros_ec_dev *ec);
>> +int cros_ec_get_lightbar_version(struct cros_ec_dev *ec, uint32_t *ver_ptr,
>> +                                uint32_t *flg_ptr);
>> +
>>  int cros_ec_get_sensor_count(struct cros_ec_dev *ec);
>>
>>  /**
>>
>> base-commit: 1e7913ff5f9f1b73146ad8522958bd266f22a510
>> --
>> Sent by a computer, using git, on the internet
>>