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    Subject[PATCH] DevFS support for /dev/cpu/X/(cpuid|msr)
    Hi,

    Please find attached a patch to add support for devfs to the i386 cpuid and
    msr drivers. Not only that, but it fixes a problem with loading these
    drivers as modules in that the exit hooks on the module never run, (simply
    changing the function prototypes to include 'static' seems to fix this).

    Patch is against 2.4.17. SMP environment isn't tested, but I can't see any
    reason why it wouldn't work...

    Cheers

    Matt
    --
    "Phased plasma rifle in a forty-watt range?"
    "Hey, just what you see, pal"
    diff -ur linux-2.4.17.orig/arch/i386/kernel/cpuid.c linux-2.4.17/arch/i386/kernel/cpuid.c
    --- linux-2.4.17.orig/arch/i386/kernel/cpuid.c Sat Jan 5 19:20:08 2002
    +++ linux-2.4.17/arch/i386/kernel/cpuid.c Sun Jan 6 18:09:08 2002
    @@ -23,6 +23,11 @@
    *
    * This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on
    * an SMP box will direct the access to CPU %d.
    + *
    + * ChangeLog
    + *
    + * 2002-01-06 Matt Dainty <matt@bodgit-n-scarper.com>
    + * Added support for devfs
    */

    #include <linux/module.h>
    @@ -35,12 +40,16 @@
    #include <linux/poll.h>
    #include <linux/smp.h>
    #include <linux/major.h>
    +#include <linux/threads.h>
    +#include <linux/devfs_fs_kernel.h>

    #include <asm/processor.h>
    #include <asm/msr.h>
    #include <asm/uaccess.h>
    #include <asm/system.h>

    +static devfs_handle_t devfs_handle[NR_CPUS];
    +
    #ifdef CONFIG_SMP

    struct cpuid_command {
    @@ -140,24 +149,45 @@
    open: cpuid_open,
    };

    -int __init cpuid_init(void)
    +static int __init cpuid_init(void)
    {
    - if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) {
    + int i;
    + char name[16];
    +
    + if (devfs_register_chrdev(CPUID_MAJOR, "cpu/%d/cpuid", &cpuid_fops)) {
    printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
    CPUID_MAJOR);
    return -EBUSY;
    }
    + for(i = 0; i < NR_CPUS; i++) {
    + sprintf(name, "cpu/%d/cpuid", i);
    + if ((devfs_handle[i] = devfs_register(NULL, name, DEVFS_FL_DEFAULT,
    + CPUID_MAJOR, i,
    + S_IFCHR | S_IRUSR | S_IRGRP,
    + &cpuid_fops, NULL)) == NULL) {
    + printk(KERN_ERR "cpuid: failed to devfs_register()\n");
    + }
    + }

    return 0;
    }

    -void __exit cpuid_exit(void)
    +static void __exit cpuid_exit(void)
    {
    - unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
    + int i;
    + devfs_handle_t parent;
    +
    + for(i = 0; i < NR_CPUS; i++) {
    + parent = devfs_get_parent(devfs_handle[i]);
    + devfs_unregister(devfs_handle[i]);
    + if(devfs_get_first_child(parent) == NULL)
    + devfs_unregister(parent);
    + }
    + devfs_unregister_chrdev(CPUID_MAJOR, "cpu/%d/cpuid");
    }

    module_init(cpuid_init);
    -module_exit(cpuid_exit)
    +module_exit(cpuid_exit);

    EXPORT_NO_SYMBOLS;

    diff -ur linux-2.4.17.orig/arch/i386/kernel/msr.c linux-2.4.17/arch/i386/kernel/msr.c
    --- linux-2.4.17.orig/arch/i386/kernel/msr.c Sat Jan 5 19:20:08 2002
    +++ linux-2.4.17/arch/i386/kernel/msr.c Sun Jan 6 18:09:18 2002
    @@ -22,6 +22,11 @@
    *
    * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
    * an SMP box will direct the access to CPU %d.
    + *
    + * ChangeLog
    + *
    + * 2002-01-06 Matt Dainty <matt@bodgit-n-scarper.com>
    + * Added support for devfs
    */

    #include <linux/module.h>
    @@ -34,12 +39,16 @@
    #include <linux/poll.h>
    #include <linux/smp.h>
    #include <linux/major.h>
    +#include <linux/threads.h>
    +#include <linux/devfs_fs_kernel.h>

    #include <asm/processor.h>
    #include <asm/msr.h>
    #include <asm/uaccess.h>
    #include <asm/system.h>

    +static devfs_handle_t devfs_handle[NR_CPUS];
    +
    /* Note: "err" is handled in a funny way below. Otherwise one version
    of gcc or another breaks. */

    @@ -248,24 +257,45 @@
    open: msr_open,
    };

    -int __init msr_init(void)
    +static int __init msr_init(void)
    {
    - if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
    + int i;
    + char name[16];
    +
    + if (devfs_register_chrdev(MSR_MAJOR, "cpu/%d/msr", &msr_fops)) {
    printk(KERN_ERR "msr: unable to get major %d for msr\n",
    MSR_MAJOR);
    return -EBUSY;
    }
    + for(i = 0; i < NR_CPUS; i++) {
    + sprintf(name, "cpu/%d/msr", i);
    + if ((devfs_handle[i] = devfs_register(NULL, name, DEVFS_FL_DEFAULT,
    + MSR_MAJOR, i,
    + S_IFCHR | S_IRUSR | S_IRGRP | S_IWUSR,
    + &msr_fops, NULL)) == NULL) {
    + printk(KERN_ERR "msr: failed to devfs_register()\n");
    + }
    + }

    return 0;
    }

    -void __exit msr_exit(void)
    +static void __exit msr_exit(void)
    {
    - unregister_chrdev(MSR_MAJOR, "cpu/msr");
    + int i;
    + devfs_handle_t parent;
    +
    + for(i = 0; i < NR_CPUS; i++) {
    + parent = devfs_get_parent(devfs_handle[i]);
    + devfs_unregister(devfs_handle[i]);
    + if(devfs_get_first_child(parent) == NULL)
    + devfs_unregister(parent);
    + }
    + devfs_unregister_chrdev(MSR_MAJOR, "cpu/%d/msr");
    }

    module_init(msr_init);
    -module_exit(msr_exit)
    +module_exit(msr_exit);

    EXPORT_NO_SYMBOLS;
    \
     
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