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char: misc: Increase the maximum number of dynamic misc devices to 1048448

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On AmpereOne, 128 dynamic misc devices is not enough for the per-cpu
coresight_tmc devices.  Switch the dynamic minors allocator to an ida and
add logic to allocate in the ranges [0..127] and [256..1048575], leaving
[128..255] for static misc devices.  Dynamic allocations start from 127
growing downwards and then increasing from 256, so device numbering for the
first 128 devices remain the same as before.

Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
Link: https://lore.kernel.org/r/20221114212212.9279-1-scott@os.amperecomputing.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
D Scott Phillips 2022-11-14 13:22:12 -08:00 committed by Greg Kroah-Hartman
parent 7b51161696
commit ab760791c0
1 changed files with 28 additions and 13 deletions
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41
drivers/char/misc.c
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@ -61,7 +61,29 @@ static DEFINE_MUTEX(misc_mtx);
* Assigned numbers, used for dynamic minors
*/
#define DYNAMIC_MINORS 128 /* like dynamic majors */
static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
static DEFINE_IDA(misc_minors_ida);
static int misc_minor_alloc(void)
{
int ret;
ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL);
if (ret >= 0) {
ret = DYNAMIC_MINORS - ret - 1;
} else {
ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,
MINORMASK, GFP_KERNEL);
}
return ret;
}
static void misc_minor_free(int minor)
{
if (minor < DYNAMIC_MINORS)
ida_free(&misc_minors_ida, DYNAMIC_MINORS - minor - 1);
else if (minor > MISC_DYNAMIC_MINOR)
ida_free(&misc_minors_ida, minor);
}
#ifdef CONFIG_PROC_FS
static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
@ -183,14 +205,13 @@ int misc_register(struct miscdevice *misc)
mutex_lock(&misc_mtx);
if (is_dynamic) {
int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
int i = misc_minor_alloc();
if (i >= DYNAMIC_MINORS) {
if (i < 0) {
err = -EBUSY;
goto out;
}
misc->minor = DYNAMIC_MINORS - i - 1;
set_bit(i, misc_minors);
misc->minor = i;
} else {
struct miscdevice *c;
@ -209,10 +230,7 @@ int misc_register(struct miscdevice *misc)
misc, misc->groups, "%s", misc->name);
if (IS_ERR(misc->this_device)) {
if (is_dynamic) {
int i = DYNAMIC_MINORS - misc->minor - 1;
if (i < DYNAMIC_MINORS && i >= 0)
clear_bit(i, misc_minors);
misc_minor_free(misc->minor);
misc->minor = MISC_DYNAMIC_MINOR;
}
err = PTR_ERR(misc->this_device);
@ -240,16 +258,13 @@ EXPORT_SYMBOL(misc_register);
void misc_deregister(struct miscdevice *misc)
{
int i = DYNAMIC_MINORS - misc->minor - 1;
if (WARN_ON(list_empty(&misc->list)))
return;
mutex_lock(&misc_mtx);
list_del(&misc->list);
device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
if (i < DYNAMIC_MINORS && i >= 0)
clear_bit(i, misc_minors);
misc_minor_free(misc->minor);
mutex_unlock(&misc_mtx);
}
EXPORT_SYMBOL(misc_deregister);