Date:   Thu, 10 Sep 2020 17:49:42 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Guenter Roeck <groeck@...gle.com>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Gwendal Grignou <gwendal@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH v2] platform/chrome: Don't populate lightbar device if it
 isn't there

Hi,

On 10/9/20 16:52, Guenter Roeck wrote:
> On Thu, Sep 10, 2020 at 7:32 AM Enric Balletbo i Serra
> <enric.balletbo@...labora.com> wrote:
>>
>> Hi,
>>
>> On 10/9/20 16:18, Guenter Roeck wrote:
>>> On Wed, Sep 9, 2020 at 3:42 PM Stephen Boyd <swboyd@...omium.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@...omium.org>
>>>> Cc: Guenter Roeck <groeck@...omium.org>
>>>> Cc: Lee Jones <lee.jones@...aro.org>
>>>> Signed-off-by: Stephen Boyd <swboyd@...omium.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.
>>
> 
> If that is the only reason, wouldn't it be better to use something
> else (eg dmi_match) to determine if the system in question is a  Pixel
> Chromebook (Link) ?
> 
>              if (!strcmp(ec_platform->ec_name, CROS_EC_DEV_NAME) &&
>                  (cros_ec_check_features(ec, EC_FEATURE_LIGHTBAR) ||
>                   dmi_match(DMI_PRODUCT_NAME, "Link")) {
> 

That looks a better solution, indeed. And definetely I'd prefer use the check
features way.

Gwendal, can you confirm that the Pixel Chromebook (Link) is the _only_ one
affected? This one is the only that comes to my mind but I might miss others.

I think that Samus has this flag (I can double check) and this was discussed
with you (long, long time ago :-) )

Thanks,
 Enric


> Thanks,
> Guenter
> 
>>> 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
>>>>

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