lkml.org 
[lkml]   [2011]   [Jul]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: pca953x: support working w/o platform data
On 07/04/11 09:43, Grant Likely wrote:

> On Fri, Jul 01, 2011 at 08:17:44PM +0300, Igor Grinberg wrote:
>> On 07/01/11 14:33, Christian Gmeiner wrote:
>>
>>> Provide defaults for pca953x, so the driver can be used w/o
>>> providing platform data.
>> Wouldn't it be better to provide a default pdata structure inside the driver
>> and use it in case no pdata supplied, so you will not have to patch the
>> driver all around checking each time if pdata is valid?
>
> I would agree. However, you will need to adjust the structure of the
> driver somewhat to do so. Once a device is registered, the data
> pointed to by platform_device->dev.platform_data must be treated as
> immutable by the driver, otherwise driver unbind/rebind can become
> horribly broken.

The driver already copies several field from pdata to the chip structure.
Also, chip->dyn_pdata can be used for this purpose, but instead of
allocating it dynamically, it just can be a part of the chip structure.

> I often solve this by keeping a full copy of the pdata structure in
> the driver's private data structure, and always referencing the 'safe'
> local copy instead of dereferencing dev->platform_data every time.

If this is done and the chip structure will contain all the information
needed (either flat, or in some kind of dyn_pdata), then indeed there
will be no need to access the pdata anymore.
Also, there will be no need to allocate pdata in pca953x_get_alt_pdata()
function.
I think this would be the most clean and safe way.

--
Regards,
Igor.



\
 
 \ /
  Last update: 2011-07-04 09:47    [W:0.036 / U:1.324 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site