Change file permissions after upload

[alided]

Hi,

I'm posting a comment with file attachment to a FeedItem using REST inside public chatter group.

The file is uploaded and the comment get's created. However the file is not visible in the comment, but i can see the uploaded file in the chatter file browser. It says visible only to me.

 In one of the posts(http://boards.developerforce.com/t5/Chatter-and-Chatter-API/Attach-a-file-to-a-Chatter-Comment-via-S... there was a suggestion to set origin to be Chatter, i tried both it didn't change anything, file was still visible only to me.

The interesting part is when i create a FeedItem with attachment i do see the attachment inside the FeedItem, and the file has visibility to a group in which i post.

Is there a way to change file permission after i uploaded it was unable to find it in the API ?

Thanks

Albert

[Jia Hu]

Use ContentDocumentLink object to create your sharing links,..
http://www.salesforce.com/us/developer/docs/api/Content/sforce_api_objects_contentdocumentlink.htm