Commit ab760791 authored by D Scott Phillips's avatar D Scott Phillips Committed by Greg Kroah-Hartman
Browse files

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



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: default avatarD Scott Phillips <scott@os.amperecomputing.com>
Link: https://lore.kernel.org/r/20221114212212.9279-1-scott@os.amperecomputing.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7b511616

drivers/char/misc.c

+28 −13
Original line number Diff line number Diff line
@@ -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);