Re: [PATCH v2 3/3] firmware: xilinx: Add sysfs support for feature config

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Sep 13, 2021 at 01:39:55AM -0700, Ronak Jain wrote:
> Add support for sysfs interface for runtime features configuration.
>  The user can configure the features at runtime. First the user need
>  to select the config id of the supported features and then the user
>  can configure the parameters of the feature based on the config id.
>  So far the support is added for the over temperature and external
>  watchdog features.
> 
> Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
> ---
> Changes in v2:
> - Update commit message
> ---
>  drivers/firmware/xilinx/zynqmp.c | 71 ++++++++++++++++++++++++++++++++
>  1 file changed, 71 insertions(+)
> 
> diff --git a/drivers/firmware/xilinx/zynqmp.c b/drivers/firmware/xilinx/zynqmp.c
> index 875d13bc1a57..a1434dd368f2 100644
> --- a/drivers/firmware/xilinx/zynqmp.c
> +++ b/drivers/firmware/xilinx/zynqmp.c
> @@ -1361,6 +1361,75 @@ static DEVICE_ATTR_RW(pggs1);
>  static DEVICE_ATTR_RW(pggs2);
>  static DEVICE_ATTR_RW(pggs3);
>  
> +static atomic_t feature_conf_id;

Why does this have to be an atomic?

And shouldn't this be per-device, not global to all devices in the
system?

> +
> +static ssize_t feature_config_id_show(struct device *device,
> +				      struct device_attribute *attr,
> +				      char *buf)
> +{
> +	return sysfs_emit(buf, "%d\n", atomic_read(&feature_conf_id));
> +}
> +
> +static ssize_t feature_config_id_store(struct device *device,
> +				       struct device_attribute *attr,
> +				       const char *buf, size_t count)
> +{
> +	u32 config_id;
> +	int ret;
> +
> +	if (!buf)
> +		return -EINVAL;

How can there ever be a NULL buffer?

No need to check for impossible things.

thanks,

greg k-h