Messages in this thread | | | From | John Ogness <> | Subject | Re: [PATCH v2] tty: ttynull: implement console write | Date | Wed, 15 Feb 2023 16:24:23 +0106 |
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On 2023-02-15, Petr Mladek <pmladek@suse.com> wrote: > That said, the current code is error-prone. The check for non-NULL > con->write is too far from the caller.
con->write is supposed to be immutable after registration, so having the check "far from the caller" is not a real danger.
console_emit_next_record() is the toplevel function responsible for printing on a particular console so I think it is appropriate that the check is made when determining if this function should be called. I also think console_is_usable() is the proper place for the NULL check to reside since that is the function that determines if printing is allowed.
> I would prefer to make it more safe. For example, I would prevent > registration of consoles without con->write callback in the first > place. It would require, to implement the empty write() callback > for ttynull console as done by this patch.
I would prefer that we do not start encouraging dummy implementations. If you insist on con->write having _some_ value other than NULL, then we could define some macro with a special value (CONSOLE_NO_WRITE). But then we have to check that value. IMHO, allowing NULL is not an issue.
John Ogness
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