Messages in this thread | | | Date | Mon, 04 Jul 2011 10:45:03 +0300 | From | Igor Grinberg <> | Subject | Re: pca953x: support working w/o platform data |
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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.
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