linux-kernel - Re: [PATCH 2/2] block, char_dev: Use correct format specifier for unsigned ints

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Message-ID: <4ed3b9d5-ea65-ef7d-6377-62aeae44c5a3@csail.mit.edu>
Date:   Tue, 6 Feb 2018 11:58:36 -0800
From:   "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     logang@...tatee.com, axboe@...nel.dk, jlayton@...chiereds.net,
        bfields@...ldses.org, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] block, char_dev: Use correct format specifier for
 unsigned ints

On 2/6/18 2:24 AM, Greg KH wrote:
> On Mon, Feb 05, 2018 at 06:25:27PM -0800, Srivatsa S. Bhat wrote:
>> From: Srivatsa S. Bhat <srivatsa@...il.mit.edu>
>>
>> register_blkdev() and __register_chrdev_region() treat the major
>> number as an unsigned int. So print it the same way to avoid
>> absurd error statements such as:
>> "... major requested (-1) is greater than the maximum (511) ..."
>> (and also fix off-by-one bugs in the error prints).
>>
>> While at it, also update the comment describing register_blkdev().
>>
>> Signed-off-by: Srivatsa S. Bhat <srivatsa@...il.mit.edu>
>> ---
>>
>>  block/genhd.c |   19 +++++++++++--------
>>  fs/char_dev.c |    4 ++--
>>  2 files changed, 13 insertions(+), 10 deletions(-)
>>
>> diff --git a/block/genhd.c b/block/genhd.c
>> index 88a53c1..21a18e5 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -308,19 +308,22 @@ void blkdev_show(struct seq_file *seqf, off_t offset)
>>  /**
>>   * register_blkdev - register a new block device
>>   *
>> - * @major: the requested major device number [1..255]. If @major = 0, try to
>> - *         allocate any unused major number.
>> + * @major: the requested major device number [1..BLKDEV_MAJOR_MAX-1]. If
>> + *         @major = 0, try to allocate any unused major number.
>>   * @name: the name of the new block device as a zero terminated string
>>   *
>>   * The @name must be unique within the system.
>>   *
>>   * The return value depends on the @major input parameter:
>>   *
>> - *  - if a major device number was requested in range [1..255] then the
>> - *    function returns zero on success, or a negative error code
>> + *  - if a major device number was requested in range [1..BLKDEV_MAJOR_MAX-1]
>> + *    then the function returns zero on success, or a negative error code
>>   *  - if any unused major number was requested with @major = 0 parameter
>>   *    then the return value is the allocated major number in range
>> - *    [1..255] or a negative error code otherwise
>> + *    [1..BLKDEV_MAJOR_MAX-1] or a negative error code otherwise
>> + *
>> + * See Documentation/admin-guide/devices.txt for the list of allocated
>> + * major numbers.
>>   */
>>  int register_blkdev(unsigned int major, const char *name)
>>  {
>> @@ -347,8 +350,8 @@ int register_blkdev(unsigned int major, const char *name)
>>  	}
>>  
>>  	if (major >= BLKDEV_MAJOR_MAX) {
>> -		pr_err("register_blkdev: major requested (%d) is greater than the maximum (%d) for %s\n",
>> -		       major, BLKDEV_MAJOR_MAX, name);
>> +		pr_err("register_blkdev: major requested (%u) is greater than the maximum (%u) for %s\n",
>> +		       major, BLKDEV_MAJOR_MAX-1, name);
>>  
>>  		ret = -EINVAL;
>>  		goto out;
>> @@ -375,7 +378,7 @@ int register_blkdev(unsigned int major, const char *name)
>>  		ret = -EBUSY;
>>  
>>  	if (ret < 0) {
>> -		printk("register_blkdev: cannot get major %d for %s\n",
>> +		printk("register_blkdev: cannot get major %u for %s\n",
>>  		       major, name);
>>  		kfree(p);
>>  	}
>> diff --git a/fs/char_dev.c b/fs/char_dev.c
>> index 33c9385..a279c58 100644
>> --- a/fs/char_dev.c
>> +++ b/fs/char_dev.c
>> @@ -121,8 +121,8 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
>>  	}
>>  
>>  	if (major >= CHRDEV_MAJOR_MAX) {
>> -		pr_err("CHRDEV \"%s\" major requested (%d) is greater than the maximum (%d)\n",
>> -		       name, major, CHRDEV_MAJOR_MAX);
>> +		pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
>> +		       name, major, CHRDEV_MAJOR_MAX-1);
>>  		ret = -EINVAL;
>>  		goto out;
>>  	}
> 
> Thanks for both of these patches, if Al doesn't grab them, I will after
> 4.16-rc1 comes out.
> 

Sounds great! Thank you!

Regards,
Srivatsa