Spread and attitudes to slave literacy

Mar 2015
Some slave States forbade by law teaching literacy to slaves - and also free negroes.
Not all did.
How widespread was slave literacy in southern States, and what were the social attitudes to it?

And I mean not just teaching slaves to read for ideological/abolitionist/religious reasons. Rather, slaves who were literate with approval of owners who regarded it as practically convenient.

How common was it for owners to receive, and expect to receive, letters written by a slave at home while travelling away from home?

In the States where slave literacy was illegal, how common were actual prosecutions of owners for the crime of owning a literate slave?
In the States where law did not forbid slave literacy, were owners of literate slaves threatened by social disapproval?

David Vagamundo

Ad Honorem
Jan 2010
Atlanta, Georgia USA
As to your first question, W. E. B. Du Bois estimated about 5% of slaves were literate in 1860 in Black Reconstruction. Eugene Genovese thought that percent was possibly low. See Roll, Jordan, Roll; The World the Slaves Made, Part 2, which has a chapter on the subject.

However, most white southerners thought literacy for slaves was a very dangerous thing. See Genovese.
Mar 2015
There were 4 000 000 slaves in 1860, and 300 000 slaveowners.
What could have been the fraction of slaveowners who had one or more literate slave and approved? A master who did not have all slaves literate, or most slaves literate, but a few or one slaves who were trusted to be literate - house nigger, slave overseer or such.