On Thu, Apr 08, 2021 at 09:48:38AM +0200, Oliver Neukum wrote: > Am Mittwoch, den 07.04.2021, 12:28 +0200 schrieb Johan Hovold: > > TIOCSSERIAL is a horrid, underspecified, legacy interface which for most > > serial devices is only useful for setting the close_delay and > > closing_wait parameters. > > > > A non-privileged user has only ever been able to set the since long > > deprecated ASYNC_SPD flags and trying to change any other *supported* > > feature should result in -EPERM being returned. Setting the current > > values for any supported features should return success. > > > > Fix the cdc-acm implementation which instead indicated that the > > TIOCSSERIAL ioctl was not even implemented when a non-privileged user > > set the current values. > > Hi, > > the idea here was that you are setting something else, if you are > not changing a parameter that can be changed. That conclusion is > dubious, but at the same time, this implementation can change > only these two parameters. So can the test really be dropped > as opposed to be modified? The de-facto standard for how to handle change requests for non-supported features (e.g. changing the I/O port or IRQ) is to simply ignore them and return 0. For most (non-legacy) serial devices the only relevant parameters are close_delay and closing_wait. And as we need to return -EPERM when a non-privileged user tries to change these, we cannot drop the test. (And returning -EOPNOTSUPP was never correct as the ioctl is indeed supported.) Johan
