Re: [PATCH] configfs: implement binary attributes

[Krzysztof Opasiak]

W dniu 2015-12-30 o 00:00, Joel Becker pisze:
> On Thu, Dec 24, 2015 at 03:51:10PM +0100, Christoph Hellwig wrote:
>> From: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
>>
>> ConfigFS lacked binary attributes up until now. This patch
>> introduces support for binary attributes in a somewhat similar
>> manner of sysfs binary attributes albeit with changes that
>> fit the configfs usage model.
>>
>> Problems that configfs binary attributes fix are everything that
>> requires a binary blob as part of the configuration of a resource,
>> such as bitstream loading for FPGAs, DTBs for dynamically created
>> devices etc.
>
> Overall, I really like this addition.
>
>> @@ -423,7 +429,9 @@ static int configfs_attach_attr(struct 
configfs_dirent * sd, struct dentry * den
>>   	spin_unlock(&configfs_dirent_lock);
>>
>>   	error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | 
S_IFREG,
>> -				configfs_init_file);
>> +				(sd->s_type & CONFIGFS_ITEM_ATTR) ?
>> +					configfs_init_file :
>> +					configfs_init_bin_file);
>
> BIN_ATTRs are the more uncommon type, at least for now.  I would think
> this code should check for special cases and fall back to ITEM_ATTR.  So
> reverse it.
>
> 	(sd->s_type & CONFIGFS_ITEM_BIN_ATTR) ?
>    		configfs_init_bin_file :
> 		configfs_init_file
>

I think that static inline helper can be usefull here to improve readability

>> +static ssize_t
>> +configfs_read_bin_file(struct file *file, char __user *buf,
>> +		       size_t count, loff_t *ppos)
>> +{
>> +	struct configfs_buffer *buffer = file->private_data;
>> +	struct dentry *dentry = file->f_path.dentry;
>> +	struct config_item *item = to_item(dentry->d_parent);
>> +	struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
>> +	ssize_t retval = 0;
>> +	ssize_t len = min_t(size_t, count, PAGE_SIZE);
>> +
>> +	mutex_lock(&buffer->mutex);
>> +
>> +	/* we don't support switching read/write modes */
>> +	if (buffer->write_in_progress) {
>> +		retval = -EINVAL;
>> +		goto out;
>> +	}
>
> These are valid arguments, it's just competing with another operation.
> Wouldn't something like EINPROGRESS or ETXTBSY make more sense and be
> more informative?  The same for configfs_write_bin_file().
>
> Joel
>

--
Krzysztof Opasiak
Samsung R&D Institute Poland
Samsung Electronics
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