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

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Message-ID: <5B8DA87D05A7694D9FA63FD143655C1B9DAA3809@hasmsx108.ger.corp.intel.com>
Date:   Tue, 12 Feb 2019 15:22:27 +0000
From:   "Winkler, Tomas" <tomas.winkler@...el.com>
To:     cgxu519 <cgxu519@....com>, Greg KH <gregkh@...uxfoundation.org>
CC:     "arnd@...db.de" <arnd@...db.de>,
        "linux-kernel@...r.kernel.org" <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.

I guess this was a boilerplate code, but I'm sure we don't need so many devices.

Thanks
Tomas