[PATCH 09/11] staging: comedi: comedi_buf: clarify comedi_buf_read_alloc()

Ian Abbott abbotti at mev.co.uk
Wed Jan 2 19:03:08 UTC 2013


On 02/01/2013 18:10, H Hartley Sweeten wrote:
> On Wednesday, January 02, 2013 6:52 AM, Ian Abbott wrote:
>> On 2012-12-21 16:42, H Hartley Sweeten wrote:
>>> Clarify the check to make sure the number of bytes to allocate is
>>> available.
>>>
>>> Signed-off-by: H Hartley Sweeten <hsweeten at visionengravers.com>
>>> Cc: Ian Abbott <abbobbi at mev.co.uk>
>>> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
>>> ---
>>>    drivers/staging/comedi/comedi_buf.c | 8 ++++----
>>>    1 file changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
>>> index 246f577..1ec5aaa 100644
>>> --- a/drivers/staging/comedi/comedi_buf.c
>>> +++ b/drivers/staging/comedi/comedi_buf.c
>>> @@ -298,10 +298,10 @@ EXPORT_SYMBOL(comedi_buf_read_n_available);
>>>    /* allocates a chunk for the reader from filled (and munged) buffer space */
>>>    unsigned comedi_buf_read_alloc(struct comedi_async *async, unsigned nbytes)
>>>    {
>>> -	if ((int)(async->buf_read_alloc_count + nbytes - async->munge_count) >
>>> -	    0) {
>>> -		nbytes = async->munge_count - async->buf_read_alloc_count;
>>> -	}
>>> +	int available = async->munge_count - async->buf_read_alloc_count;
>>
>> Minor nit-pick: that should be an unsigned int.
>
> Will the munge_count always be larger, or equal, to the buf_read_alloc_count?
> The original code had the (int) cast so I wasn't sure. If so, then yes the variable
> should be an unsigned int.

Well the value it is being compared to (nbytes) is an unsigned int, so 
the int value (available) will be converted to unsigned int before the 
comparison anyway.  So making 'available' an unsigned int to begin with 
shouldn't break anything that isn't already broke!

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti at mev.co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-





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