Messages in this thread Patch in this message | | | From | Thadeu Lima de Souza Cascardo <> | Subject | [PATCH 3/3] misc: use a proper range for minor number dynamic allocation | Date | Mon, 9 Nov 2009 22:30:17 -0200 |
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The current dynamic allocation of minor number for misc devices has some drawbacks.
First of all, the range for dynamic numbers include some statically allocated numbers. It goes from 63 to 0, and we have numbers in the range from 1 to 15 already allocated. Although, it gives priority to the higher and not allocated numbers, we may end up in a situation where we must reject registering a driver which got a static number because a driver got its number with dynamic allocation. Considering fs/dlm/user.c allocates as many misc devices as lockspaces are created, and that we have more than 50 users around, it's not unreasonable to reach that situation.
The proposed solution uses the not yet reserved range from 64 to 127. If more devices are needed, we may push 64 to 16.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com> --- drivers/char/misc.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/char/misc.c b/drivers/char/misc.c index 59fff30..5681d3c 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -60,6 +60,7 @@ static DEFINE_MUTEX(misc_mtx); /* * Assigned numbers, used for dynamic minors */ +#define DYNAMIC_MINOR_BASE 64 #define DYNAMIC_MINORS 64 /* like dynamic majors */ static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS); @@ -206,7 +207,7 @@ int misc_register(struct miscdevice * misc) mutex_unlock(&misc_mtx); return -EBUSY; } - misc->minor = DYNAMIC_MINORS - i - 1; + misc->minor = DYNAMIC_MINOR_BASE + i; set_bit(i, misc_minors); } @@ -215,7 +216,7 @@ int misc_register(struct miscdevice * misc) misc->this_device = device_create(misc_class, misc->parent, dev, misc, "%s", misc->name); if (IS_ERR(misc->this_device)) { - int i = DYNAMIC_MINORS - misc->minor - 1; + int i = misc->minor - DYNAMIC_MINOR_BASE; if (i < DYNAMIC_MINORS && i >= 0) clear_bit(i, misc_minors); err = PTR_ERR(misc->this_device); @@ -244,7 +245,7 @@ int misc_register(struct miscdevice * misc) int misc_deregister(struct miscdevice *misc) { - int i = DYNAMIC_MINORS - misc->minor - 1; + int i = misc->minor - DYNAMIC_MINOR_BASE; if (list_empty(&misc->list)) return -EINVAL; -- 1.6.3.3
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