"ここに名前を書くだけでいいですか？" means "Is it ok to just write [my] name here?"
I'm confused about where でいい comes from.
http://www.guidetojapanese.org/learn/grammar/must#part5 is about conjugating ていい /でいい to adjectives and verbs.
I don't know which grammar rules are applied when でいい is conjugated to nouns as in "ここに名前を書くだけでいいですか？".
Can anyone tell me?