Many functionality is accessed through ioctl callback, what permission is needed before invoking ioctl?
On Sat, Apr 2, 2022 at 8:45 PM Gregory Nutt <spudan...@gmail.com> wrote: > If I understand correctly we can add one single "dummy_read" implementation > > for all drivers that do not supply the read method. This will ensure that > > O_RDOK is always supported if file permissions allow it. > > > > There aren't any file permissions. The entire access is controlled by NULL > and non-NULL read/write methods. > > That is the way that it has worked. if you check, I think you will find > that all of the existing IOCTL drivers already have dummy read and > sometimes write methods. Being consistent is important to the integrity of > the OS. Whatever you all decide to do, make sure that is is consistent > across all drivers. > > The semantics are: NULL read -> write only, NULL write -> read only. Both > NULL -> the driver is broken. > > I don't understand how checking if the pointer is NULL would support > read-only, or write-only behavior. I think we would be losing > functionality and this is important in other drivers where read and write > actually matter. >
