svn commit: r223722 - in head/sys: kern sys

Peter Jeremy peterjeremy at acm.org
Sat Jul 2 22:25:25 UTC 2011


On 2011-Jul-02 11:13:57 -0400, Ben Kaduk <minimarmot at gmail.com> wrote:
>On Sat, Jul 2, 2011 at 9:54 AM, Ed Schouten <ed at freebsd.org> wrote:
>>  Reintroduce the cioctl() hook in the TTY layer for digi(4).

Thanks Ed.

>>  The cioctl() hook can be used by drivers to add ioctls to the *.init and
>>  *.lock devices. This commit breaks the ttydevsw ABI, since this
>
>Aren't __FreeBSD_version bumps cheap, these days?

A __FreeBSD_version bump can help a driver determine whether specific
functionality is available in the kernel but that doesn't solve this
particular issue.

A struct ttydevsw is allocated and populated by a TTY device driver
and passed to the generic TTY code to define callbacks from the
generic code into the driver.  Consider the case where a module
compiled with an old struct ttydevsw definition is loaded into a new
kernel - the generic TTY code will attempt to reference ttydevsw
fields that aren't defined by the driver, with results that won't be
pretty.

-- 
Peter Jeremy
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