Change sd_open, sd_close and sd_ioctl to use this lock to ensure
serialization of some critical operations, thus avoiding some
race conditions. Ideas picked from NetBSD (ccd and sd devices).
This fixes one of the problems noted in PR kern/3688.
Reviewed by: "Justin T. Gibbs" <gibbs@plutotech.com>
from last time. Some people have pointed out that there were some odd
side-effects in the changes I made. Two things are different:
- sc_print_addr() will print 'foodev0:' (i.e. sd0:, st0:, cd0:, etc...)
if the device name is known. If it's not known, it'll use a longer
notation. This shortens error messages back to a sane length.
- Added a small function called sc_print_init() to set the sc_printing
flag so that sc_print_addr() will know that we want it to print a
linefeed. Used this in scsi_device_attach() to restore proper carriage
return printing behavior which I broke.
Remaining bogons: the NCR SCSI driver prints out information while the
device-specific attach routine is running with its own linefeeds. This
breaks up the individual messages emitted by the subdriver modules and
causes at least one message to appear on a line by itself without a
device spec prefix. I'm not sure of the correct way to fix this, and
I don't have any NCR SCSI hardware to test with anyway.
There's probably more, but I gather that a rewrite of the SCSI subsystem
is pending anyway, so I'll leave the rest to Those Who Know More About
This Than I (tm).
("Hey! Who made _you_ the keeper of all things BSDish?!") but this has
bugged me for a long time, and now that I finally have the chance
to hack on it (and test the results), I'll take my chances. I can also
point to other BSD implementations for precedents if you put my back to
the wall.
The only thing that's changed is how the messages are formatted. Now,
instead of having this:
aha0 at 0x330-0x333 irq 11 drq 5 on isa
(aha0:3:0): "HP C1553A 9503" type 1 removable SCSI 2
st0(aha0:3:0): Sequential-Access density code 0x24, variable blocks, write-enabled
(aha0:3:1): "HP C1553A 9503" type 8 removable SCSI 2
ch0(aha0:3:1): Medium-Changer 6 slot(s) 1 drive(s) 0 arm(s) 0 i/e-slot(s)
We have this:
aha0 at 0x330-0x333 irq 11 drq 5 on isa
scbus0 at aha0 bus 0
st0 at scbus0 target 3 lun 0
st0: <HP C1553A 9503> type 1 removable SCSI 2
st0: Sequential-Access density code 0x24, variable blocks, write-enabled
ch0 at scbus0 target 3 lun 1
ch0: <HP C1553A 9503> type 8 removable SCSI 2
ch0: Medium-Changer 6 slot(s) 1 drive(s) 0 arm(s) 0 i/e-slot(s)
Which is (to me anyway) is a lot more pleasant to look at. (Call me
crazy -- g'head: you know you wanna -- but the previous messages remind
me of Linux. Ever see the output from the linux device probes? It's a mess
of copyright notices, version numbers/dates, author e-mail addresses and
other crap. Let's not go there, okay? Bleh.)
Notice that devices are now specified in terms of the scsi bus they
live on rather than the adapter. This better reflects the contents
of the kernel config file (if you use wired-down device specifications
anyway) and removes some ambiguity that may arise if you have a multi-
channel adapter with more than one bus.
Also, sc_print_addr() now generates messages like this:
st0 at scbus0 target 3 lun 0: NOT READY asc:3a,0 Medium not present
instead of this:
st0(aha0:3:0): NOT READY asc:3a,0 Medium not present
I also added a quirk entry for the HP Superstore 12000e 6 tape DAT
autoloader, which needs SC_MORE_LUS in order for the changer device
to be properly probed and attached. (I'm working on a chcontrol utility
to manipulate the changer on this drive which should hopefully be general
enough to work with other changers too. If you want the prototype I have
now, it's at ftp://skynet.ctr.columbia.edu/pub/freebsd/changer.c.)
Remaining bugs:
- The 'foodev0: yadda yadda yadda' bits should probably be printed entirely
by the device-specific subdriver attach code instead of half by the
scsi_device_attach() routine and half by the device specific attach
routine like it is now.
- The wired-down device specifications in the kernel config file should
be used to control bus/device probing to some extent rather than just
for choosing names for devices we find. If the config says there's a
device at scbus0 target 0 lun 0 called sd0, we should look there and
check for a device that can be managed by the sd driver. If we don't
find one, we should probably complain that there's no device there or
that there is a device but of the wrong type. Once all the devices from
the wired down list have been probed, the code can then autodetect and
autoattach any devices that remain unassigned.
- Apparently some tape changers (hi Ulf!) return 'not ready/medium not
present' when the magazine is loaded but a tape has not been put in the
drive yet. This causes an open(/dev/ch0) to fail and prevents you from
using the changer.c utility to load the first tape into the drive. My
HP changer does not behave this way. The workaround is to manually load
a tape into the drive before attempting to use the changer program, but
you can get in trouble if you accidentally eject a tape without loading
a new one and you're at a remote location: you won't be able to load
any tapes anymore. I'm not sure what the correct software solution is
for this but ideally there should be one.
- I should not be doing this: I'm the NIS guru, not the SCSI guru.
(This is not my beautiful code. How did I get here? My god: what
have I done?)
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
Added CONTROL device that only does user-ioctl and nothing else;
Added protection so user-ioctl requires write access;
Clean up scsiconf.h a little. It needs more work.
sd.c: Julian's removal of subdriver requests
st.c, scsi_tape.h: Julian's suport of compressed tape drives
Note: compressed tape drives are still not working fully.
scsiconf.h, scsi_base.c, scsi_driver.c: address problems in probes
and error console logs
