Based on the kobject structure, but much smaller and simpler to use.

Against Jon's cdev stuff

The existing cdev interface requires users to deal with the embedded
kobject in two places:

- The kobject name field must be set before adding the cdev, and
- Should cdev_add() fail, a call to kobject_put() is required.

IMO, this exposure of the embedded kobject makes the interface more brittle
and harder to understand.  It's also unnecessary.  With the removal of
/sys/cdev, a call to cdev_del() will nicely replace kobject_put(), and the
name setting is easily wrapped.

This is against 2.6.4, but depends on the /sys/cdev removal patch.

This is the first of two patches designed to make life easier for authors
of device driver books - and, with luck, driver authors too.

/sys/cdev is, according to Al, a mistake which was never really meant to
exist.  I believe nothing uses it currently - there isn't a whole lot there
to use.  Its existence takes up system resources, and also requires drivers
to deal with the cdev's embedded kobject in their failure paths.  The
following patch (against 2.6.4) makes it all go away.

OK, almost all.  We have to keep (but not register) cdev_subsys because
it's rwsem is needed to control access to cdev_map.

Patch adds sysfs simple class support for DRI character device (Major
226).  Also, adds some error checking.

I noticed that the class_register() function in drivers/base/class.c
always returns 0 and thus will never fail.  Patch below inserts simple
error checking to return any errors if they occur.  Feedback welcome.
Thanks,

Patch adds sysfs simple class support for netlink character device
(Major 36).  Feedback appreciated.  Thanks,

The only spot that seems to care about class_simple_device_add possibly
failing, but it gets the wrong error test.

Error path doesn't class_simple_destroy.

Doesn't catch error on class_simple_add, and existing error return paths
forget to class_simple_destroy.

Error condition isn't caught on class_simple_create, and
parport_register_driver failure doesn't do proper cleanup.

* Hanna Linder (hannal@us.ibm.com) wrote:
> +		ppp_class = class_simple_create(THIS_MODULE, "ppp");
> +		class_simple_device_add(ppp_class, MKDEV(PPP_MAJOR, 0), NULL, "ppp");

What happens if that class_simple_create() fails?  Actually,
class_simple_device_add could fail too, but doesn't seem anybody is
checking for that.

>  		err = devfs_mk_cdev(MKDEV(PPP_MAJOR, 0),
>  				S_IFCHR|S_IRUSR|S_IWUSR, "ppp");
> -		if (err)
> +		if (err) {
>  			unregister_chrdev(PPP_MAJOR, "ppp");
> +			class_simple_device_remove(MKDEV(PPP_MAJOR,0));
> +		}

need to destroy the class on error path to avoid leak.

> @@ -2540,6 +2547,7 @@ static void __exit ppp_cleanup(void)
>  	if (unregister_chrdev(PPP_MAJOR, "ppp") != 0)
>  		printk(KERN_ERR "PPP: failed to unregister PPP device\n");
>  	devfs_remove("ppp");
> +	class_simple_device_remove(MKDEV(PPP_MAJOR, 0));

ditto.  this will leak and would cause oops on reload of module.

something like below.

This got fixed in 2.4, but somehow got missed in 2.6.

This is a cleaner fix for the previous bogon fix.

- Move free_block prototype, and ac_entry and ac_data functions up in file.

- Use list_for_each_entry in cpuup_callback.

- Remove unneccessary g_cpucache_up in cpuup_callback.

- Make reap_timer_func take CPU number as data, and check if that is
  offline before rescheduing (noop without CONFIG_HOTPLUG_CPU).

Levent Serinol <levent.serinol@mynet.com> found that the hotplug cpu
patch broke Sparc64.  I introduced a num_possible_cpus(), which
Sparc64 already has.  Remove the Sparc64 one.

I also removed Sparc64's cpu_online() macro: it's in linux/cpumask.h
already.

Note that without CONFIG_HOTPLUG_CPU, online cpus == possible cpus, so
substitutions are a noop.

- Changes show_stat to print out stats for every possible cpu, not
  just online CPUs.

- Allocate mem in stat_open on possible, not online_cpus.

- Add conventient macros to cpu.h: especially cpu_is_offline() for
  testing if a cpu is still online.

- Add a num_possible_cpus() similar to num_online_cpus(), and define
  cpu_possible_mask for UP.

- Allow printk on down cpus once system is running.

- Mask cpumask with possible, not online cpus, for sys_getaffinity().

Extracts core of drain_pages() for hotcpu use.  Trivial.

Hotplug CPU needs to drain pages on a downed CPU (usually it's the
current cpu).  Introduce "__drain_pages", make the CPU an argument,
and expose it if CONFIG_HOTPLUG_CPU as well as CONFIG_PM.

into ppc970.osdl.org:/home/torvalds/v2.5/linux

into redhat.com:/spare/repo/via-crypto-2.5

into ppc970.osdl.org:/home/torvalds/v2.5/linux

Promise driver uses a custom error handling function, so we need
the fix that was applied to the libata core:  the SCSI error
handling thread requires that we complete commands using a special
completion function, since the normal one doesn't work inside
the error handling thread.

The following patch is a very crude one to at least not make sata block
suspend-to-ram entirely. Probably you want more powermanagement handling as
well... but it's a start

into ppc970.osdl.org:/home/torvalds/v2.5/linux

The pcnet32 driver will hang after a few frames (<30) with the 79C971
(and probably the 79C972 though I don't have the hardware to prove it).
By interrupting slightly more frequently the hang will not occur.

>>>>> "Pawel" == Pawel Sokolowski <falcon@muflon.linux.pl> writes:

Pawel> This machine has RAM BIOS booted from floppy. I ran it and EISA
Pawel> configure utility to check this once more. Card is enabled and not
Pawel> locked. I added eisa_bus.enable_dev=2 parameter but it didn't help much.
Pawel> I'm getting:

Pawel> EISA: Probing bus 0 at eisa0
Pawel> EISA: Mainboard HWPC061 detected.
Pawel> EISA: slot 2 : HWP1940 detected (forced enabled).
Pawel> EISA: Detected 1 card.

Pawel> I added this final entry you mailed but nothing changed. Still - module
Pawel> loads and unloads cleanly and without any warnings on 2.6.4-rc1. But
Pawel> does nothing - not a single line in logs/dmesg after it's loaded. Card
Pawel> does not work after modprobe, I can't get interface up.

Ok, found it.

It really looks like the new EISA probing code in hp100 never got
tested, since a precious offset has disappeared during the rewriting
process.

Please note that you still need to enable the device by hand, since
your BIOS (or maybe the EISA CFG file, since I'm seeing the exact same
problem on a Compaq machine here) doesn't properly enable the card.

Here is what I'm getting on my test system :

EISA: Probing bus 0 at 0000:00:0f.0
EISA: Mainboard CPQ0541 detected.
EISA: slot 1 : DEC4250 detected.
EISA: slot 2 : UNB0048 detected.
EISA: slot 3 : HWP1940 detected (forced enabled).
hp100: Using (slow) programmed i/o mode.
hp100: at 0x3c38, IRQ 3, EISA bus, 128k SRAM (rx/tx 75%).
hp100: Adapter is attached to 10Mb/s network (10baseT).
EISA: slot 4 : NVL0701 detected.

Now we've moved the bogolock code out to stop_machine.c and
generalized it a little, use it in module.c and delete the duplicate
code there.

The "bogolock" code was introduced in module.c, as a way of freezing
the machine when we wanted to remove a module.  This patch moves it
out to stop_machine.c and stop_machine.h.

Since the code changes affinity and proirity, it's impolite to hijack
the current context, so we use a kthread.  This means we have to pass
the function rather than implement "stop_machine()" and
"restart_machine()".

into ppc970.osdl.org:/home/torvalds/v2.5/linux

into ppc970.osdl.org:/home/torvalds/v2.5/linux

into kernel.bkbits.net:/home/davem/sparc-2.6

into ppc970.osdl.org:/home/torvalds/v2.5/linux

into austin.ibm.com:/shaggy/bk/jfs-2.5