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Date:   Tue, 24 Mar 2020 18:46:42 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc:     linux-kernel@vger.kernel.org,
        nicholas.johnson-opensource@outlook.com.au
Subject: Re: [PATCH 3/3] nvmem: core: use is_bin_visible for permissions
Message-ID: <20200324174642.GA2524667@kroah.com>
References: <20200324171600.15606-1-srinivas.kandagatla@linaro.org>
 <20200324171600.15606-4-srinivas.kandagatla@linaro.org>
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On Tue, Mar 24, 2020 at 05:16:00PM +0000, Srinivas Kandagatla wrote:
> By using is_bin_visible callback to set permissions will remove a large list
> of attribute groups. These group permissions can be dynamically derived in
> the callback.
> 
> Suggested-by: Greg KH <gregkh@linuxfoundation.org>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> ---
>  drivers/nvmem/nvmem-sysfs.c | 74 +++++++++----------------------------
>  1 file changed, 18 insertions(+), 56 deletions(-)
> 
> diff --git a/drivers/nvmem/nvmem-sysfs.c b/drivers/nvmem/nvmem-sysfs.c
> index 8759c4470012..1ff1801048f6 100644
> --- a/drivers/nvmem/nvmem-sysfs.c
> +++ b/drivers/nvmem/nvmem-sysfs.c
> @@ -103,6 +103,17 @@ static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
>  
>  	return count;
>  }
> +static umode_t nvmem_bin_attr_is_visible(struct kobject *kobj,
> +					 struct bin_attribute *attr, int i)
> +{
> +	struct device *dev = container_of(kobj, struct device, kobj);
> +	struct nvmem_device *nvmem = to_nvmem_device(dev);
> +
> +	if (nvmem->root_only)
> +		return nvmem->read_only ? 0400 : 0600;
> +
> +	return nvmem->read_only ? 0444 : 0644;
> +}

I don't know why this is so hard for me to read, but how about this
instead:

static umode_t nvmem_bin_attr_is_visible(struct kobject *kobj,
					 struct bin_attribute *attr, int i)
{
	struct device *dev = container_of(kobj, struct device, kobj);
	struct nvmem_device *nvmem = to_nvmem_device(dev);
	umode_t mode = 0400;

	if (!nvmem->root_only)
		mode |= 0044;

	if (!nvmem->read_only)
		mode |= 0200;

	return mode;
}

Did I get the logic corect?

thanks,

greg k-h