linux-kernel - Re: [PATCH 2/2] chardev: showing minor range for chardev in the output of /proc/devices

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Date:   Tue, 12 Feb 2019 23:18:22 +0800
From:   cgxu519 <cgxu519@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 2/2] chardev: showing minor range for chardev in the
 output of /proc/devices

On 2/12/19 5:02 PM, Greg KH wrote:
> On Tue, Feb 12, 2019 at 04:47:39PM +0800, Chengguang Xu wrote:
>> Currently chardev allows to share major, showing
>> major with minor range for chardev will be more
>> helpful.
>>
>> Signed-off-by: Chengguang Xu <cgxu519@....com>
>> ---
>>   fs/char_dev.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/char_dev.c b/fs/char_dev.c
>> index b25b1da097d5..6f00acdeb308 100644
>> --- a/fs/char_dev.c
>> +++ b/fs/char_dev.c
>> @@ -55,7 +55,9 @@ void chrdev_show(struct seq_file *f, off_t offset)
>>   	mutex_lock(&chrdevs_lock);
>>   	for (cd = chrdevs[major_to_index(offset)]; cd; cd = cd->next) {
>>   		if (cd->major == offset)
>> -			seq_printf(f, "%3d %s\n", cd->major, cd->name);
>> +			seq_printf(f, "%3d %s (%u-%u)\n", cd->major, cd->name,
>> +				   cd->baseminor,
>> +				   cd->baseminor + cd->minorct - 1);
> You are changing the format of a userspace file, what tools are going to
> break when you do this?

I'll remove this part in V2. Do you have any idea how to get the minor
range info for particular major? Or adding a similar file to somewhere
under /sys is acceptable?

Thanks