Re: [PATCH v2 1/2] driver core: Move the "removable" attribute from USB to core

Krzysztof Wilczyński
2021-05-12T01:00:56Z

Hi Rajat,

I have few questions below, but to add in advance, I might be confusing
the role that "type->supports_removable" and "dev->removable" plays
here, and if so then I apologise.

[...]
> @@ -2504,8 +2523,16 @@ static int device_add_attrs(struct device *dev)
> goto err_remove_dev_online;
> }
>
> + if (type && type->supports_removable) {
> + error = device_create_file(dev, &dev_attr_removable);
> + if (error)
> + goto err_remove_dev_waiting_for_supplier;
> + }
> +
> return 0;

Would a check for "dev->removable == DEVICE_REMOVABLE" here be more
appropriate?

Unless you wanted to add sysfs objects when the device hints that it has
a notion of being removable even though it might be set to "unknown" or
"fixed" (if that state is at all possible then), and in which case using
the dev_is_removable() helper would also not be an option since it does
a more complex check internally.

Technically, you could always add this sysfs object (similarly to what
USB core did) as it would then show the correct state depending on
"dev->removable".

Also, I suppose, it's not possible for a device to have
"supports_removable" set to true, but "removable" would be different
than "DEVICE_REMOVABLE", correct?

[...]
> +enum device_removable {
> + DEVICE_REMOVABLE_UNKNOWN = 0,
> + DEVICE_REMOVABLE,
> + DEVICE_FIXED,
> +};

I know this was moved from the USB core, but I personally find it
a little bit awkward to read, would something like that be acceptable?

enum device_removable {
DEVICE_STATE_UNKNOWN = 0,
DEVICE_STATE_REMOVABLE,
DEVICE_STATE_FIXED,
};

The addition of state to the name follows the removable_show() function
where the local variable is called "state", and I think it makes sense
to call this as such. What do you think?

> +static inline bool dev_is_removable(struct device *dev)
> +{
> + return dev && dev->type && dev->type->supports_removable
> + && dev->removable == DEVICE_REMOVABLE;
> +}

Similarly to my question about - would a simple check to see if
"dev->removable" is set to "DEVICE_REMOVABLE" here be enough?

Krzysztof