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SubjectRe: [char-misc-next 2/3] mei: adding sysfs fw_status attribute
On Wed, Jul 24, 2013 at 06:41:56PM +0300, Tomas Winkler wrote:
> Export fw status register through sysfs interface.
> The interface is for applications that monitors
> fw health.
>
> Signed-off-by: Natalia Ovsyanikov <natalia.ovsyanikov@intel.com>
> Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
> ---
> drivers/misc/mei/main.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 51 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
> index 173ff09..64e36a8 100644
> --- a/drivers/misc/mei/main.c
> +++ b/drivers/misc/mei/main.c
> @@ -659,6 +659,44 @@ out:
> return mask;
> }
>
> +/**
> + * mei_show_fw_status - mei device attribute show method
> + *
> + * @dev: device pointer
> + * @attr: attribute pointer
> + * @buf: char out buffer
> + *
> + * returns number of the bytes, printed into the buffer
> + */
> +
> +static ssize_t mei_show_fw_status(struct device *device,
> + struct device_attribute *attr, char *buf)
> +{
> + struct mei_device *dev = dev_get_drvdata(device);
> + u32 fw_status;
> + int err;
> +
> + mutex_lock(&dev->device_lock);
> + err = mei_fw_status(dev, &fw_status);
> + mutex_unlock(&dev->device_lock);
> + if (err) {
> + dev_err(device, "attribute show: read fw_status error = %d\n",
> + err);
> + return err;
> + }
> +
> + dev_dbg(device, "attribute show: fw_status 0x%x\n", fw_status);
> + return sprintf(buf, "%08X\n", fw_status);
> +}
> +static DEVICE_ATTR(fw_status, S_IRUGO, mei_show_fw_status, NULL);
> +static struct attribute *mei_attributes[] = {
> + &dev_attr_fw_status.attr,
> + NULL
> +};
> +static const struct attribute_group mei_attr_group = {
> + .attrs = mei_attributes,
> +};
> +
> /*
> * file operations structure will be used for mei char device.
> */
> @@ -685,17 +723,22 @@ static struct miscdevice mei_misc_device = {
> .minor = MISC_DYNAMIC_MINOR,
> };
>
> -
> int mei_register(struct mei_device *dev)
> {
> + struct device *device = &dev->pdev->dev;
> int ret;
> - mei_misc_device.parent = &dev->pdev->dev;
> +
> + mei_misc_device.parent = device;
> ret = misc_register(&mei_misc_device);
> if (ret)
> return ret;
>
> + ret = sysfs_create_group(&device->kobj, &mei_attr_group);
> + if (ret)
> + return ret;

And you just lost the race with userspace (you told it you had a device,
it went and scanned your attributes and saved them, then you registered
more...)

Please use the dev_groups field for your class to properly have the
driver core register these before userspace is told about the device,
that's the correct way to do this.

thanks,

greg k-h


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