Re: [patch] staging: comedi: cleanup comedi_recognize()

[Ian Abbott <abbotti@mev.co.uk>]

On 2012-06-06 10:49, Dan Carpenter wrote:
> On Wed, Jun 06, 2012 at 11:45:43AM +0200, walter harms wrote:
>>
>>
>> Am 06.06.2012 11:28, schrieb Ian Abbott:
>>> On 2012-06-05 12:01, Dan Carpenter wrote:
>>>> On Tue, Jun 05, 2012 at 12:06:10PM +0200, walter harms wrote:
>>>>> Hi all,
>>>>> the patch is fine with me but i have a few basic questions:
>>>>>
>>>>> Why the (void  *) at all ? it returns a name what is a const char *.
>>>>>
>>>>
>>>> We're really returning a pointer to a private struct, it's just that
>>>> the first element on the struct always has to be a pointer to char *.
>>>
>>> To be pedantic, it's really returning a pointer to some member of type
>>> 'const char *' within a private struct.  To make life easier for
>>> themselves, those drivers make that the first member of the private
>>> struct so a void pointer to the member is also a void pointer to the
>>> struct.
>>>
>>
>> I do not like it. It is confusing.
>
> Yep.

But at least the confusion is concentrated in a single place!  From the 
individual drivers' point of view it's fairly simple (as long as it puts 
the 'const char pointer to board name' member at the top of its private 
data structure).

>> Are these struct comedi_driver *driv of different size every time ?
>
> Nope.

It's the private board information data structures for each driver that 
are different sizes, but the size is passed in the comedi comedi_driver 
'offset' member along with the 'board_name' and 'num_names' members. 
Not all drivers set those members and just use the 'driver_name' to 
match any supported device, but I digress.

-- 
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