Re: [PATCH 00/16] tty: TIOCSSERIAL fixes and clean ups

On Wed, Apr 07, 2021 at 12:23:18PM +0200, Johan Hovold wrote:

TIOCSSERIAL is a horrid, underspecified, legacy interface which for most
serial devices is only useful for setting the close_delay and
closing_wait parameters.

This series fixes up the various ways in which driver authors have
gotten the implementation wrong over the years, like, for example,
jiffies conversions, permissions checks and error handling.

The de-facto standard for error handling is to ignore any unsupported
features and immutable parameters (cf. UPF_FIXED_PORT and deprecated
ASYNC flags).

Permission checking should prevent an unprivileged user from changing
anything but the ASYNC_USR flags (and custom divisor) by returning
-EPERM.

These patches are against tty-next, but the staging ones could otherwise
go through either tree.

I've taken all of these through my tty tree, thanks for cleaning this
mess up.

greg k-h