linux-kernel - Re: [PATCH] mei: expand minor range when registering chrdev region

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Date:   Tue, 12 Feb 2019 22:55:03 +0800
From:   cgxu519 <cgxu519@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     tomas.winkler@...el.com, arnd@...db.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mei: expand minor range when registering chrdev region

On 2/12/19 5:29 PM, Greg KH wrote:
> On Tue, Feb 12, 2019 at 02:02:52PM +0800, Chengguang Xu wrote:
>> Actually, total amount of available minor number
>> for a single major is MINORMARK + 1. So expand
>> minor range when registering chrdev region.
>>
>> Signed-off-by: Chengguang Xu <cgxu519@....com>
>> ---
>>   drivers/misc/mei/main.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
>> index 87281b3695e6..3df54f1e1a8b 100644
>> --- a/drivers/misc/mei/main.c
>> +++ b/drivers/misc/mei/main.c
>> @@ -869,7 +869,7 @@ static const struct file_operations mei_fops = {
>>   
>>   static struct class *mei_class;
>>   static dev_t mei_devt;
>> -#define MEI_MAX_DEVS  MINORMASK
>> +#define MEI_MAX_DEVS  (MINORMASK + 1)
> Why is this needed?  Have you really run out of that many minor nodes
> for this driver?

Not really, practically maybe we cannot reach to the limit.
I was just curious why only one minor number left there and assumed
that was from a mistake(since I've seen similar mistake in other driver).
However, if it explicitly sets to MINORMASK for some reasons, then it's
better to keep as is.

Thanks