After I removed all the unit2minor()/minor2unit() calls from the kernel
yesterday, I realised calling minor() everywhere is quite confusing.
Character devices now only have the ability to store a unit number, not
a minor number. Remove the confusion by using dev2unit() everywhere.
This commit could also be considered as a bug fix. A lot of drivers call
minor(), while they should actually be calling dev2unit(). In -CURRENT
this isn't a problem, but it turns out we never had any problem reports
related to that issue in the past. I suspect not many people connect
more than 256 pieces of the same hardware.
Reviewed by: kib
the device indicates that it wasn't able to write all the data in the
buffer out.
Ed Schouten doesn't like the idea of a panic here. I think for
production code, we need something better. For right now, while we're
trying to assess the impact of this issue, a panic is OK. So complain
to me, not him if this is hit.
The last half year I've been working on a replacement TTY layer for the
FreeBSD kernel. The new TTY layer was designed to improve the following:
- Improved driver model:
The old TTY layer has a driver model that is not abstract enough to
make it friendly to use. A good example is the output path, where the
device drivers directly access the output buffers. This means that an
in-kernel PPP implementation must always convert network buffers into
TTY buffers.
If a PPP implementation would be built on top of the new TTY layer
(still needs a hooks layer, though), it would allow the PPP
implementation to directly hand the data to the TTY driver.
- Improved hotplugging:
With the old TTY layer, it isn't entirely safe to destroy TTY's from
the system. This implementation has a two-step destructing design,
where the driver first abandons the TTY. After all threads have left
the TTY, the TTY layer calls a routine in the driver, which can be
used to free resources (unit numbers, etc).
The pts(4) driver also implements this feature, which means
posix_openpt() will now return PTY's that are created on the fly.
- Improved performance:
One of the major improvements is the per-TTY mutex, which is expected
to improve scalability when compared to the old Giant locking.
Another change is the unbuffered copying to userspace, which is both
used on TTY device nodes and PTY masters.
Upgrading should be quite straightforward. Unlike previous versions,
existing kernel configuration files do not need to be changed, except
when they reference device drivers that are listed in UPDATING.
Obtained from: //depot/projects/mpsafetty/...
Approved by: philip (ex-mentor)
Discussed: on the lists, at BSDCan, at the DevSummit
Sponsored by: Snow B.V., the Netherlands
dcons(4) fixed by: kan
This changes the naming of USB serial devices to: /dev/ttyU%d and
/dev/cuaU%d for call-in and call-out devices respectively. (Please
notice: capital 'U')
Please also note that we now have .init and .lock devices for USB
serial ports. These are not persistent across device removal. devd(8)
can be used to configure them on attachment time.
These changes also improve the chances of the system surviving if
the USB device is unplugged at an inconvenient time. At least we
do not rip things apart while there are any threads in the device
driver anymore.
Remove cdevsw, rely on the tty generic one.
Don't make_dev(), use ttycreate() which does all the magic.
In detach, do close procesing if we ripped things apart
while the device was open. Call ttyfree() once we're done
cleaning up.
copies.
No current line disciplines have a dynamically changing hotchar, and
expecting to receive anything sensible during a change in ldisc is
insane so no locking of the hotchar field is necessary.
debugging levels to off by default. Now that debug levels can be
tweaked by sysctl we don't need to go through hoops to get the
different usb parts to produce debug data.
