Re: [PATCH] configfs: implement binary attributes

Pantelis Antoniou
2015-12-30T08:51:17Z

Hi Joel,

> On Dec 30, 2015, at 01:00 , Joel Becker <jlbec@evilplan.org> wrote:
>
> On Thu, Dec 24, 2015 at 03:51:10PM +0100, Christoph Hellwig wrote:
>> From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
>>
>> 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.
>

That’s good :)

>> @@ -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
>

OK.

>> +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().
>

Yep, will be done.

> Joel
>

Regards

— Pantelis

PS. A big thanks to Christoph for keeping this going. I will shortly post a new version with the
requested changes incorporated.

> --
>
> "Soap and education are not as sudden as a massacre, but they are more
> deadly in the long run."
> - Mark Twain
>
>
> http://www.jlbec.org/
> jlbec@evilplan.org