Message-ID: <54414200.1090901@acm.org>
Date:	Fri, 17 Oct 2014 11:21:20 -0500
From:	Corey Minyard <minyard@....org>
To:	Thomas Renninger <trenn@...e.de>
CC:	linux-kernel@...r.kernel.org,
	openipmi-developer@...ts.sourceforge.net
Subject: Re: [patch 2/3] ipmi: Remove ipmi_major module parameter and define
 global IPMI_MAJOR

On 10/17/2014 02:55 AM, Thomas Renninger wrote:
> Hi,
>
> On Tuesday, October 14, 2014 08:26:26 PM Corey Minyard wrote:
>> Sorry to top post on this, but you attached the file, so it's hard to reply
>> inline.
>>
>> There's no way this can go in.  There's not enough major device numbers
>> for all the devices that exist, we have mechanisms to handle dynamically
>> assigning numbers, and the IPMI driver just isn't important enough to
>> warrant it's own major device number.
> Hm, I always get 248, on 2 different machines. Just luck?
> If 248 is still free (and according to major.h it is), why not?

That's only because you are loading the same modules and have similar
hardware, I'm sure.  Just luck.

But primarily, that's not the way it's done.  My understanding is that
nobody
gets major numbers any more.  There's just not enough room.

>
>> The particular mechanism to pass in the major number was just a temporary
>> measure.  It is no longer really necessary and could be removed.
> Ok, if I read above right, you mean:
> The module param to specify the major number can vanish.
> But I must not try to invent a new MAJOR_IPMI definition in major.h.
> Instead the whole thing can be dynamic (use MKDEV, remember the return
> value and use it later to freeing again).

Well, IPMI is registered into the sysfs framework and gets a dynamically
allocated major number, so udev takes care of creating the device node.
So there should be no need to do anything on a properly configured system.
No mkdev, no remembering.

-corey


>
> Thanks,
>
>      Thomas
>
>  
>> -corey
>>
>> On 10/14/2014 09:40 AM, trenn@...e.de wrote:
>>
>> There should be no need to specify the major number of /dev/ipmiX via module
>> parameter. Others do not need this as well.
>> This is the way msr.c (/dev/cpu/X/msr) is doing it as well.
>>
>> Side effect of this patch will be that the userspace interface cannot
>> be disabled at kernel level anymore. But this can also be enforced by not
>> letting userspace create the device file /dev/ipmiX.
>>
>> Signed-off-by: Thomas Renninger <trenn@...e.de>
>> CC: minyard@....org
>>
>> Index: kernel_ipmi/drivers/char/ipmi/ipmi_devintf.c
>> ===================================================================
>> --- kernel_ipmi.orig/drivers/char/ipmi/ipmi_devintf.c
>> +++ kernel_ipmi/drivers/char/ipmi/ipmi_devintf.c
>> @@ -39,6 +39,7 @@
>>  #include <linux/spinlock.h>
>>  #include <linux/slab.h>
>>  #include <linux/ipmi.h>
>> +#include <linux/major.h>
>>  #include <linux/mutex.h>
>>  #include <linux/init.h>
>>  #include <linux/device.h>
>> @@ -867,14 +868,6 @@ static const struct file_operations ipmi
>>
>>  #define DEVICE_NAME     "ipmidev"
>>
>> -static int ipmi_major;
>> -module_param(ipmi_major, int, 0);
>> -MODULE_PARM_DESC(ipmi_major, "Sets the major number of the IPMI device. 
>> By" -		 " default, or if you set it to zero, it will choose the next"
>> -		 " available device.  Setting it to -1 will disable the"
>> -		 " interface.  Other values will set the major device number"
>> -		 " to that value.");
>> -
>>  /* Keep track of the devices that are registered. */
>>  struct ipmi_reg_list {
>>  	dev_t            dev;
>> @@ -887,7 +880,7 @@ static struct class *ipmi_class;
>>
>>  static void ipmi_new_smi(int if_num, struct device *device)
>>  {
>> -	dev_t dev = MKDEV(ipmi_major, if_num);
>> +	dev_t dev = MKDEV(IPMI_MAJOR, if_num);
>>  	struct ipmi_reg_list *entry;
>>
>>  	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
>> @@ -906,7 +899,7 @@ static void ipmi_new_smi(int if_num, str
>>
>>  static void ipmi_smi_gone(int if_num)
>>  {
>> -	dev_t dev = MKDEV(ipmi_major, if_num);
>> +	dev_t dev = MKDEV(IPMI_MAJOR, if_num);
>>  	struct ipmi_reg_list *entry;
>>
>>  	mutex_lock(&reg_list_mutex);
>> @@ -932,9 +925,6 @@ int __init init_ipmi_devintf(void)
>>  {
>>  	int rv;
>>
>> -	if (ipmi_major < 0)
>> -		return -EINVAL;
>> -
>>  	printk(KERN_INFO "ipmi device interface\n");
>>
>>  	ipmi_class = class_create(THIS_MODULE, "ipmi");
>> @@ -943,20 +933,16 @@ int __init init_ipmi_devintf(void)
>>  		return PTR_ERR(ipmi_class);
>>  	}
>>
>> -	rv = register_chrdev(ipmi_major, DEVICE_NAME, &ipmi_fops);
>> +	rv = register_chrdev(IPMI_MAJOR, DEVICE_NAME, &ipmi_fops);
>>  	if (rv < 0) {
>>  		class_destroy(ipmi_class);
>> -		printk(KERN_ERR "ipmi: can't get major %d\n", ipmi_major);
>> +		printk(KERN_ERR "ipmi: can't get major %d\n", IPMI_MAJOR);
>>  		return rv;
>>  	}
>>
>> -	if (ipmi_major == 0) {
>> -		ipmi_major = rv;
>> -	}
>> -
>>  	rv = ipmi_smi_watcher_register(&smi_watcher);
>>  	if (rv) {
>> -		unregister_chrdev(ipmi_major, DEVICE_NAME);
>> +		unregister_chrdev(IPMI_MAJOR, DEVICE_NAME);
>>  		class_destroy(ipmi_class);
>>  		printk(KERN_WARNING "ipmi: can't register smi watcher\n");
>>  		return rv;
>> @@ -977,5 +963,5 @@ void cleanup_ipmi_dev(void)
>>  	mutex_unlock(&reg_list_mutex);
>>  	class_destroy(ipmi_class);
>>  	ipmi_smi_watcher_unregister(&smi_watcher);
>> -	unregister_chrdev(ipmi_major, DEVICE_NAME);
>> +	unregister_chrdev(IPMI_MAJOR, DEVICE_NAME);
>>  }
>> Index: kernel_ipmi/include/uapi/linux/major.h
>> ===================================================================
>> --- kernel_ipmi.orig/include/uapi/linux/major.h
>> +++ kernel_ipmi/include/uapi/linux/major.h
>> @@ -173,6 +173,8 @@
>>
>>  #define VIOTAPE_MAJOR		230
>>
>> +#define IPMI_MAJOR              248
>> +
>>  #define BLOCK_EXT_MAJOR		259
>>  #define SCSI_OSD_MAJOR		260	/* open-osd's OSD scsi device 
> */
>

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